Light Charged Particles Induced Nuclear Reactions on Some Medium Weight Nuclei for Practical Applications

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Ain Shams University Faculty of Science Physics Department

Light Charged Particles Induced Nuclear Reactions on some Medium Weight Nuclei for Practical Applications

Thesis Submitted for the Partial Fulfillment of Master Degree in Physics (Nuclear Physics)

Bahaa Mohamed Ali Mohamed Mohsena

BSc. in Physics 2004

Physics Department- Faculty of Science

Ain Shams University

Egypt

2011

Ain Shams University Faculty of Science Physics Department

Light Charged Particles Induced Nuclear Reactions on some Medium Weight Nuclei for Practical Applications

Thesis Submitted for the Partial Fulfillment of Master Degree in Physics (Nuclear Physics)

Bahaa Mohamed Ali Mohamed Mohsena

BSc. in Physics 2004

Supervised by

Prof.Dr. Samir Yousha El Kameesy Prof. of Nuclear Physics Physics Department Faculty of Science Ain Shams University

Prof.Dr. Usama Seddik Abd Alghafar Prof. of Nuclear and Particle Physics Physics Department Nuclear Research Center Atomic Energy Authority

Dr. Mogahed Ibrahim Al Abyad Lecturer of Nuclear Physics Physics Department Nuclear Research Center Atomic Energy Authority Ain Shams University Faculty of Science Physics Department Approval Sheet

Light Charged Particles Induced Nuclear Reactions on some Medium Weight Nuclei for Practical Applications

Name of Candidate

Bahaa Mohamed Ali Mohamed Mohsena

Supervised by Signature

Prof.Dr. Samir Yousha El Kameesy

Prof.Dr. Usama Seddik Abd Alghafar

Dr. Mogahed Ibrahim Al Abyad

Acknowledgment

ACKNOWLEDGMENT

All thanks go first to ALLAH. I would like to thank Prof. Dr. Samir El-Kameesy for his kindness, support, continuous encouragement and guidance during this study. I would like to thank deeply Prof. Dr. Usama Seddik for his scientific supervision and kind help for me from my first day in the AEA cyclotron project. He showed steady interest and provided constant guidance and encouragement during this study. I would like to give special great thanks to my supervisor Dr. Mogahed Al-Abyad for suggesting the subject of this thesis. His scientific supervision, guidance, support, encouragement and contribution in the experimental work are highly appreciated. I am highly indebted to him for his investigations and carrying out the theoretical nuclear reaction model calculations. I would like to thank Dr. Ditrói, Institute of Nuclear Research of the Hungarian Academy of Science, ATOMKI, Debrecen, Hungary for establishing this work in his laboratory. My great thanks go also for Prof. Dr. Tárkányi and Dr. Takács. I wish to express my great thanks for both cyclotron crews in Inshas Egypt and Debrecen Hungary. This work would have not been possible without the efforts of them. My special thanks go to my father, mother and wife.

Bahaa Mohamed Ali Cairo, 2011

I Abstract

ABSTRACT

The radioisotopes of indium, cadmium and tin have many practical and medical applications. Their standard routes for production are proton or deuteron induced reactions on natural or enriched cadmium or tin. The production via 3He induced reactions on natural or enriched cadmium was rarely discussed.

In this study 3He induced reactions on natural cadmium were measured utilizing the stacked-foil technique. The primary incident beam energy was 27 MeV extracted from the MGC-20E cyclotron, Debrecen, Hungary. The excitation functions for the reactions natCd(3He,x)115g,111mCd, 117m,g,116m,115m,114m,113m,111g,110m,g,109g,108g,107gIn and 117m,113g,111,110Sn were evaluated. The data were compared with the available literature data.

Different theoretical nuclear reaction models were also used to predict the cross sections for those reactions. The used models were ALICE-IPPE, TALYS-1.2 and EMPIRE-03. The experimental data were compared also to the theoretical model calculations. The theoretical models did not describe most of the experimental results.

The isomeric cross section ratios for the isomeric pairs 117m,gIn and 110m,gIn were calculated. The isomeric cross section ratio depends on the spins of the states of the interested isomeric pair. The calculated isomeric ratios helped to identify the mechanisms of the reactions involved.

The integral yields for some medically relevant isotopes were calculated using the excitation function curves.

Contents CONTENTS

TITLE Page ACKNOWLEDGEMENT I ABSTRACT II CONTENTS III LIST OF FIGURES VI LIST OF TABLES VIII SUMMARY X CHAPTER 1: INTRODUCTION AND LITRATURE REVIEW 1.1. RADIOACTIVITY 1 1.2. ISOTOPES 2 1.2.1. PRODUCTION OF ISOTOPES 2 1.2.2. APPLICATION OF RADIOISOTOPES 3 1.3. FUNDAMENTALS OF NUCLEAR REACTIONS 5 1.3.1. NUCLEAR REACTION ENERGETIC 7 1.3.2. REACTION THRESHOLD ENERGIES 8 1.3.3. REACTION CROSS SECTION 10 1.3.3.1. CROSS SECTION MEASUREMENT 12 1.3.3.2. TARGET YIELD 15 1.3.4. REACTION CHANNELS 17 1.3.5. STOPPING POWER AND RANGE 17 1.3.6. NUCLEAR REACTION MECHANISMS 22 1.3.6.1. COMPOUND NUCLEAR REACTIONS 23 1.3.6.2. DIRECT REACTIONS 25 1.3.6.3. PRECOMPOUND REACTIONS 26 1.4. BASICS OF GAMMA RAY DETECTORS 27 1.4.1. SCINTILLATION DETECTORS 28 1.4.2. SEMICONDUCTOR DETECTOR 29 1.4.3. THE DETECTOR EFFICIENCY 32 1.4.3.1. ABSOLUTE EFFICIENCY 32

III

Contents

1.4.3.2. INTRINSIC EFFICIENCY 33 1.4.3.3. RELATIVE EFFICIENCY 33 1.5. LITERATURE REVIEW 34 1.6. AIM OF THE WORK 35 CHAPTER 2: APPARATUS AND EXPERIMENTAL TECHNIQUES 2.1. THE CLASSICAL CYCLOTRON 38 2.2. THE AVF CYCLOTRON 41 2.3. IRRADIATION BY MGC-20 CYCLOTRON 41 2.3.1. MAGNET 43 2.3.2. ACCELERATING CHAMPER 44 2.3.3. RESONANCE SYSTEM 44 2.3.4. ION SOURCE 45 2.3.5. GAS SUPPLY SYSTEM OF THE ION SOURCE 46 2.3.6. VACUUM SYSTEM 46 2.3.7. WATER COOLING SYSTEM 46 2.3.8. BEAM EXTRACTION SYSTEM 47 2.3.9. BEAM MONITORING AND DIAGNOSTICS 47 2.3.10. BEAM TRANSPORT SYSTEM 48 3 2.4. IRRADIATION BY He 49 2.5. STACKED-FOIL TECHNIQUE 50 2.6. TARGET PREPARATION 51 2.7. ACTIVITY MEASUREMENT 54 CHAPTER 3: THEORETICAL CALCULATIONS 3.1. ALICE-IPPE 58 3.2. TALYS-1.2 60 3.3. EMPIRE-03 (ARCOLA) 65 CHAPTER 4: RESULTS AND DISCUSSION 4.1. EXCITATION FUNCTIONS OF TIN ISOTOPES 76 117m 4.1.1. FORMATION OF Sn 76 113g 4.1.2. FORMATION OF Sn 78 111 4.1.3. FORMATION OF Sn 80

Contents 110 4.1.4. FORMATION OF Sn 82 4.2. EXCITATION FUNCTIONS OF INDIUM 83 ISOTOPES 117m,g 4.2.1. FORMATION OF In 83 116m 4.2.2. FORMATION OF In 86 115m 4.2.3. FORMATION OF In 87 114m 4.2.4. FORMATION OF In 89 113m 4.2.5. FORMATION OF In 90 111g 4.2.6. FORMATION OF In 92 110m,g 4.2.7. FORMATION OF In 93 109g 4.2.8. FORMATION OF In 96 108g 4.2.9. FORMATION OF In 98 107g 4.2.10. FORMATION OF In 99 4.3. EXCITATION FUNCTIONS OF CADMIUM 101 ISOTOPES 115g 4.3.1. FORMATION OF Cd 101 111m 4.3.2. FORMATION OF Cd 102 4.4. ISOMERIC CROSS SECTION RATIOS 104 117m,g 4.4.1. ISOMERIC CROSS SECTION RATIO OF In 104 110m,g 4.4.2. ISOMERIC CROSS SECTION RATIO OF In 106 4.5. YIELD CALCULATIONS 108 CONCLUSION 112 REFERENCES 114 ARABIC SUMMARY XI

List of Figures LIST OF FIGURES

Figure Page number Caption Fig. 1.1 Growth of daughter activity A(t) normalized to 16 saturation activity Asat plotted against time normalized to the half-life of the daughter (t1/2). The slope of the tangent on the A(t)/(Asat) vs. t curve at t = 0, defined as the activation yield (Y), is also shown. Fig. 1.2 Collisions of charged particle with an atom, depending 18 on the relative sizes of the impact parameter b and atomic radius a. Fig. 1.3 The shape of the collision stopping power curve as a 21 function of the charged particle kinetic energy E. Fig. 1.4 Formation nuclear reaction of the compound nucleus 24 51Cr through various entrance channels and decay through various exit channels. Fig. 1.5 At higher energies, it’s more likely that additional 25 neutrons will evaporate from the compound nucleus. Fig. 1.6 Schematic energy spectrum of particles emitted at a 27 given angle and for a specific residual nucleus as a consequence of a nuclear reaction. The dashed curve represents the compound nuclear contribution. The discrete peaks at the high energy end correspond to direct reaction contribution. Fig. 1.7 Schematic diagram of a scintillation counter. 29 Fig. 1.8 Comparison of NaI(Tl) and HPGe spectra for 99mTc. 30 Fig. 1.9 A symple schematic electronic system for gamma 31 spectrometry. Fig. 2.1 Schematic diagram of a classical cyclotron. 39 Fig. 2.2 Magnetic pole of AVF cyclotron with and without spiral 41 angels. Fig. 2.3 Schematic diagram of the MGC-20 cyclotron. 43 Fig. 2.4 The Hungarian MGC-20E cyclotron. 44 Fig. 2.5 Proton beam profile. 48 Fig. 2.6 Hungarian beam transport Line. 49 Fig. 2.7 Schematic arrangement for target and monitor stacked- 51 foils.

List of Figures Fig. 2.8 Cross section of a typical HPGe detector. 54 Fig. 2.9 Live photo of the HPGe detector and the system of data 55 acquisition. Fig. 2.10 The efficiency curve of the detector at 12 cm source to 56 detector distance. Fig. 3.1 Flowchart of TALYS code. 64 Fig. 3.2 Flowchart of EMPIRE code. 68 Fig. 4.1 Excitation function of the monitor reaction 73 natTi(3He,x)48V. Fig. 4.2 Excitation function of 116Cd(3He,2n)117mSn reaction. 78 Fig. 4.3 Excitation function of the natCd(3He,xn)113Sn reaction. 80 Fig. 4.4 Excitation function of the natCd(3He,xn)111Sn reaction. 81 Fig. 4.5 Excitation function of the natCd(3He,xn)110Sn reaction. 83 Fig. 4.6 Excitation function of the natCd(3He,x)117gIn reaction. 85 Fig. 4.7 Excitation function of the natCd(3He,x)117mIn reaction. 85 Fig. 4.8 Excitation function of the natCd(3He,x)116mIn reaction. 87 Fig. 4.9 Excitation function of the natCd(3He,x)115mIn reaction. 88 Fig. 4.10 Excitation function of the natCd(3He,x)114mIn reaction. 90 Fig. 4.11 Excitation function of the natCd(3He,x)113mIn reaction. 91 Fig. 4.12 Excitation function of the natCd(3He,x)111gIn reaction. 93 Fig. 4.13 Excitation function of the natCd(3He,x)110gIn reaction. 95 Fig. 4.14 Excitation function of the natCd(3He,x)110mIn reaction. 95 Fig. 4.15 Excitation function of the natCd(3He,x)109gIn reaction. 97 Fig. 4.16 Excitation function of the natCd(3He,x)108gIn reaction. 99 Fig. 4.17 Excitation function of the natCd(3He,x)107gIn reaction. 100 Fig. 4.18 Excitation function of the natCd(3He,x)115gCd reaction. 102 Fig. 4.19 Excitation function of the natCd(3He,x)111mCd reaction. 104 Fig. 4.20 Isomeric cross section ratio for the isomeric pair 117m,gIn. 106 Fig. 4.21 Isomeric cross section ratio for the isomeric pair 110m,gIn. 107 Fig. 4.22 Integral yields of natCd(3He,x)110,111,113,117mSn and 115Cd 110 reactions. Fig. 4.23 Integral yields of natCd(3He,x)111,113m,114m,115m,117mIn 110 reactions. Fig. 4.24 Integral yields of natCd(3He,x)109,110m,110In reactions. 111

VII

List of Tables LIST OF TABLES

Table Caption Page Number Table. 2.1 Energy and current ranges in MGC-20 cyclotron. 42 Table. 4.1 Measured cross sections and their errors for 73 natTi(3He,x)48V. Table. 4.2 Decay data and contributing reactions of the 74 investigated products. Table. 4.3 Measured cross sections and their errors for 77 116Cd(3He,2n)117mSn. Table. 4.4 Measured cross sections and their errors for 79 natCd(3He,xn)113Sn. Table. 4.5 Measured cross sections and their errors for 81 natCd(3He,xn)111Sn. Table. 4.6 Measured cross sections and their errors for 82 natCd(3He,xn)110Sn. Table. 4.7 Measured cross sections and their errors for 84 natCd(3He,x)117m,gIn. Table. 4.8 Measured cross sections and their errors for 86 natCd(3He,x)116mIn. Table. 4.9 Measured cross sections and their errors for 88 natCd(3He,x)115mIn. Table. 4.10 Measured cross sections and their errors for 89 natCd(3He,x)114mIn. Table. 4.11 Measured cross sections and their errors for 91 natCd(3He,x)113mIn. Table. 4.12 Measured cross sections and their errors for 92 natCd(3He,x)111gIn. Table. 4.13 Measured cross sections and their errors for 94 natCd(3He,x)110m,gIn. Table. 4.14 Measured cross sections and their errors for 97 natCd(3He,x)109gIn. Table. 4.15 Measured cross sections and their errors for 98 natCd(3He,x)108gIn. Table. 4.16 Measured cross sections and their errors for 100 natCd(3He,x)107gIn.

VIII

List of Tables Table. 4.17 Measured cross sections and their errors for 101 natCd(3He,x)115gCd. Table. 4.18 Measured cross sections and their errors for 103 natCd(3He,x)111mCd. Table. 4.19 Isomeric cross section ratio in the 105 116Cd(3He,np)117m,gIn process. Table. 4.14 Isomeric cross section ratio in the 107 natCd(3He,x)110m,gIn process.

Summary SUMMARY

In this study 3He induced nuclear reactions on natural cadmium were investigated utilizing the stacked foil technique. The thesis contains four chapters;

 Chapter one (Introduction and literature review) presents historical review of the radioisotopes and their applications. The chapter presents a general introduction for the nuclear reactions fundamentals, the nuclear reactions kinematics, the nuclear reactions mechanisms, the stopping power, the reactions cross sections and the integral yield. The gamma ray spectroscopy principles are also presented. Finally the chapter presents the literature review and the aim of the work.

 Chapter two (Apparatus and experimental techniques) presents the devices and techniques included in the experimental work. The MGC-20 cyclotron and its parts, the stacked-foil technique and the HPGe detectors for activity measurement.

 Chapter three (Theoretical calculations) presents the used three theoretical nuclear reaction models; ALICE-IPP, TALYS-1.2 and EMPIRE-03.

 Chapter four (Results and discussion) presents the investigation of the excitation functions of the 3He induced nuclear reactions on natural cadmium. The formation cross sections of the radioisotopes 115g,111mCd, 117m,g,116m,115m,114m,113m,111g,110m,g,109g,108g,107gIn and 117m,113g,111,110Sn are presented. The present experimental data are compared to the previous available data. Theoretical calculations using the codes ALICE-IPPE, TALYS-1.2 and EMPIRE-03 are performed and compared to the experimental data. A disagreement is observed for most cases between theoretical and experimental data. Studying of the isomeric cross section ratios for the isomeric pairs 117m,gIn and 110m,gIn are presented. The isomeric cross section ratios for both the isomeric pairs helped to identify the mechanisms of the reactions involved. In addition the integral yields for some interesting radioisotopes are presented. Finally the conclusion is presented.

Chapter One Introduction and Literature Review

CHAPTER I INTRODUCTION AND LITERATURE REVIEW

Chapter One Introduction and Literature Review 1.1. RADIOACTIVITY

Nuclear physics as a subject distinct from atomic physics could be said to date from 1896, the year that Henri Becquerel observed that photographic plates were being fogged by an unknown radiation emanating from uranium ores. He had accidentally discovered radioactivity: the fact that some nuclei are unstable and spontaneously decay [Martin, 2006]. Rutherford started working with these newly discovered uranium rays believing that they were similar to the X-rays discovered by Röntgen [Joseph Magill and Jean Galy, 2005]. In the years that followed, the phenomenon was extensively investigated, notably by the husband and wife team of Pierre and Marie Curie and by Ernest Rutherford and his collaborators and it was established that there were three distinct types of radiation involved: these were named (by Rutherford) α, β and γ rays. In 1897 J. J. Thomson was the first to identify the cathode ray -that had been observed to occur when an electric field was established between electrodes in an evacuated glass tube- to be free electrons (the name „electron‟ had been coined in 1894 by Stoney) [Martin, 2006]. In 1900 Becquerel identified that β rays consists of electrons. And in the same year Villard and Becquerel propose that γ radiation is of electromagnetic nature; finally proven in 1914 by Rutherford and Andrade. In 1903 Rutherford proved that α radiation is shown to be ionized helium atoms. The rate of radioactive decay per unit weight was found to be fixed for any specific radioelement, no matter what its chemical or physical state was, though this rate differed greatly for different radioelements. Radioactive decay is a random process. Among the atoms in a sample undergoing decay it is not possible to identify which specific atom will be the next to decay [Gregory et al., 2002]. The activity (A) is the number of disintegrations per unit time and is proportional to the number of radioactive atoms

where (λ) is the decay constant and (N) is the number of nuclei at any time (t). Using simple mathematical treatment, the well known decay low can be obtained,

Chapter One Introduction and Literature Review 1.2. ISOTOPES

In 1913, Fajans and Soddy independently stated that each element could have atoms of different weight and with different radioactive properties, and Soddy introduced in 1914 the name isotope for different atomic species of an element. In 1913 Thomson discovered that an accelerated beam of neon atoms into two beams, corresponding to atoms having a mass number 20 and 22, when it passed through a crossed electric and magnetic field. After World War I, Aston resumed Thomson‟s work and developed mass spectrometers that could be used to measure very precisely the mass of atoms as well as their relative abundance for individual elements. He demonstrated that most elements have more than one isotope [Gregory et al., 2002]. The explanation of isotopes had to wait 20 years until a classic discovery by Chadwick in 1932. He discovered the neutron and in so doing had produced almost the final ingredient for understanding nuclei [Martin, 2006]. A nuclear species, or nuclide, is defined by (N), the number of neutrons, and (Z), the number of protons. The mass number (A) is the total number of nucleons, i.e. A = N + Z. Thus the isotopes of an element have the same number of protons i.e. same charge but different number of neutrons i.e. the same atomic number but different mass number. From this point, the isotopes have different nuclear properties but practically have identical chemical properties, since these arise from the (Z) electrons around the nucleus [Basdevant et al., 2005]. It is possible for nuclei to have the same mass number but different number of protons and different number of neutrons. Such nuclei are called isobars. Others have the same number of neutrons and different number of protons. They are called isotones. It is convenient also to identify Isomers as, the same nuclide (same Z and A) in which the nucleus is in different long lived excited states. For example, an isomer of (Tc) is (99mTc) where the (m) denotes the longest- lived excited state (i.e., a state in which the nucleons in the nucleus are not in the lowest energy state).

1.2.1. PRODUCTION OF ISOTOPES

Stable isotopes, as their name suggests, do not undergo radioactive decay. Radioactive isotopes, or radioisotopes, are available with a great variety of half lives, types of radiation, and energy [Raymond, 2009]. Of the nuclei found on Earth, the vast majority is stable. This is so because

Chapter One Introduction and Literature Review almost all short-lived radioactive nuclei have decayed during the history of the Earth. These isotopes appear in the element as mixture. There are more than 2500 isotopes; only about 270 stable and 50 radioisotopes are naturally occurring [CPEP, 2003]. All other isotopes are called artificial radioisotopes. They can be produced by nuclear reactors, by particle accelerators, or by radionuclide generators [Michael and Leo, 2007]. Generators are units that contain a radioactive “parent” nuclide with a relatively long half life that decays to a short-lived “daughter” nuclide [Powsner and Powsner, 2006]. Reactors and accelerators are producing radioisotopes through nuclear interactions by neutrons or accelerated charged particles i.e. artificially. Stable nuclides placed in or near the core of a nuclear reactor can absorb neutrons, transforming them into radioisotopes. Nuclear reactors are also used in the separation of radionuclides from fission products. These radioisotopes being neutron rich and generally decay by β- emission often accompanied by gamma- ray emission. Examples of important radioisotopes produced by different neutron induced reactions include 59Co(n.γ)60Co, and 14N(n,p)14C. To produce radioisotopes that are proton rich and that generally decay by positron emission, particle accelerators are used. Ion beams with energies ranging from hundreds of kilo-electron volts (keV) to several mega- electron volts (MeV) can be produced by accelerators such as linear accelerators and cyclotrons. Bombarding a target with such energetic ions can produce radioisotopes by a variety of nuclear reactions. Some examples are 65Cu(p,n)65Zn, 68Zn(p,2n)67Ga, 55Mn(p,pn)54Mn, and 25Mg(p,α)22Na [Shultis and Faw, 2002].

1.2.2. APPLICATION OF RADIOISOTOPES

The main advantages of using radioisotopes are ease of detection of their presence through the emanations, and the uniqueness of the identifying half-lives and radiation properties. The majority of important radionuclides applicable in science, technology, and industry have a sufficiently long half-life (months, years, tens of years, and even more) allowing long-term application, especially in the form of so-called closed radio emitters [Michael and Leo, 2007]. In 1912 Hevesy and Paneth made the first application of radioactive trace elements [Gregory et al., 2002]. Radioisotopes have found widespread use in many industrial and research activities. These applications can be categorized into four broad types of applications.

Chapter One Introduction and Literature Review

(I). TRACER APPLICATIONS: Material can be tagged with minute amounts of a radioisotope to allow it to be easily followed as it moves through some process. Some of tracer applications are flow measurements, isotope dilution, tracking of material, radiometric analysis, metabolic studies, wear and friction studies, labeled reagents, preparing tagged materials, chemical reaction mechanisms, and material separation studies.

(II). MATERIALS AFFECT RADIATION: Radiation is generally altered, either in intensity or energy, as it passes through a material. By measuring these changes, properties of the material can be determined. Such applications are density gauges, liquid level gauges, thickness gauges, neutron moisture gauges, radiation absorptiometry, and x-ray or neutron radiography.

(III). RADIATION AFFECTS MATERIALS: As radiation passes through a material, it produces ionization or changes in the electron bonds of the material, which, in turn, can alter the physical or chemical properties of the material. Such applications are radioactive catalysis, food preservation, biological growth inhibition, insect disinfestations, modification of fibers, increasing biological growth, sterile-male insect control, polymer modification, and bacterial sterilization.

(IV). ENERGY FROM RADIOISOTOPES: The energy released as a radionuclide decays is quickly transformed into thermal energy when the emitted radiation is absorbed in the surrounding medium. This thermal energy can be used as a specialized thermal energy sources or converted directly into electrical energy in electric power sources [Shultis and Faw, 2002].

Most of the radioisotopes found in nature have relatively long half lives. They also belong to elements which are not handled well by the human body. As a result medical applications generally require the use of radioisotopes which are produced artificially [Maher, 2006]. Short-lived radionuclides used in nuclear medicine can be applied in radionuclide diagnosis and therapy in the form of open radio emitters. These are called radiopharmaceuticals and are administered to the organism directly (in most cases intravenously or orally) [Michael and Leo, 2007]. In 1907 Stenbeck made the first therapeutic treatment with radium and healed skin cancer [Gregory et al., 2002]. Some of diagnostic applications are

Chapter One Introduction and Literature Review bone densitometry, Single Photon Emission Computed Tomography (SPECT), Positron Emission Tomography (PET), radioimmunoassay, diagnostic radiotracers, and radioimmunoscintigraphy. Radiation therapy has a lot of applications as teletherapy, radioimmunotherapy, clinical brachytherapy, and boron neutron capture therapy [Shultis and Faw, 2002].

The four important sub-specialties in medical physics are related to:

(I). Diagnostic imaging with x rays (diagnostic radiology physics).

(II). Diagnostic imaging with radio-nuclides (nuclear medicine physics).

(III). Treatment of cancer with ionizing radiation (radiation oncology physics).

(IV). Study of radiation hazards and radiation protection (health physics) [Podgoršak, 2006].

1.3. FUNDAMENTALS OF NUCLEAR REACTIONS

In 1919, Rutherford produced the first induced nuclear transformation in the laboratory

4He + 14N → 17O + 1H (1-3)

Rutherford used α-particles from the radioactive decay of 214Po, which have kinetic energies of 7.68 MeV. The product 17O is a stable isotope of oxygen. Joliet and I. Curie in 1934, produce radioactive nuclei in the laboratory through nuclear reactions. They used α-particles from the natural radioactive decay of polonium to bombard aluminum, thereby producing the isotope 30P, which they observed to decay through positron emission with a half life of 2.5 min to 30S [Krane, 1988].

4He + 27Al → 30P + n (1-4)

Chapter One Introduction and Literature Review The first induced nuclear reaction done in 1932 by Cockcroft and Walton using high voltage multiplier they developed to accelerate protons to 0.4 MeV [Gregory et al., 2002]. They observed the reaction

1H + 7Li → 4He + α (1-5)

The study of nuclear reactions is important for many reasons. The relative probabilities of different reactions provides information about the nuclear structure and hence an idea about the nuclear forces. It helps to obtain information about new isotopes, new particles, excited nuclear states, and elementary particles [Shirokov and Yudin, 1982]. Nuclear reactions are classified by the type of the incident radiation (projectile), bombarding energy, target, or reaction product [Meyerhof, 1967]. In the first case we distinguish: light charged particles such as electrons and positrons, heavy charged particles such as protons and α particles, and neutral particles such as neutrons. Targets are often called: light nuclei if A ≤ 40, medium nuclei if 40 < A < 150, and heavy nuclei if A ≥ 150. The collisions are classified into two categories: nuclear reactions, and scattering collisions (elastic collisions; and inelastic collisions). Nuclear reactions may entail three types of reaction mechanisms: direct, compound nucleus and preequilibrium effects. The contribution of these processes depends on the given reaction and the energy of the incident particle. The three types can be distinguished by their angular distributions and time scales. The nuclear reaction can generally represented by the equation;

or, in more compact notation, X(x,y)Y, where (X) is the target nucleus, (x) is the projectile, (Y) is the product nucleus, and (y) is the outgoing particle. The particles (x) and (y) may be elementary particles or - rays, or they may be nuclei. Hence the nuclear reaction may be represented by the set of equations,

The reactants usually are called entrance state and the products are called final state or final channel.

Chapter One Introduction and Literature Review

A number of conservation conditions apply to any reaction equation [CPEP, 2003].

 The mass number (A) and the charge (Z) must balance on each side of the reaction arrow.

 The total energy before the reaction must equal the total energy after the reaction. The total energy includes the particle kinetic energies plus the energy equivalent of the particle rest masses.

 Linear momenta before and after the reaction must be equal. For two-particle final states this means that a measurement of one particle‟s momentum determines the other particle‟s momentum.

 Quantum rules govern the balancing of the angular momentum, parity, and isospin of the nuclear levels.

1.3.1. NUCLEAR REACTION ENERGETIC

The conservation of total energy in the X(x,y)Y nuclear reaction means that;

where (mx) , (mX), (my), and (mY) represent the masses of the incident particle, target nucleus, outgoing particle, and product nucleus respectively and the (E‟s) represent kinetic energies with the assumption that the target nucleus (X) is initially at rest. The released energy of a nuclear reaction i.e. the difference between the kinetic energy of the products and that of the reactants is the so called Q- value

Because the number of protons is usually conserved in this nuclear reaction, the nuclear masses (mi) in this expression can be replaced by the corresponding atomic masses (Mi) of the particles. The electron masses on both sides of the reaction cancel each other, and the small

Chapter One Introduction and Literature Review difference in electron binding energies is negligible [Shultis and Faw, 2002]. Thus, the Q-value may also be written as,

If Q > 0, the reaction is exoergic (exothermic) and there is a net increase in the kinetic energy of the products accompanied by a net decrease in the rest mass of the products. By contrast, if Q < 0, the reaction is endoergic (endothermic), and energy is absorbed to increase the rest mass of the products. The special case of Q = 0 occurs only for elastic scattering, i.e., when mx = my and mX = mY. In inelastic scattering, mx = my but mY > mX since Y is an excited configuration of the target nucleus X and hence, Q < 0.

1.3.2. REACTION THRESHOLD ENERGIES

For reactions with Q < 0, i.e. endoergic, (or even for reactions with Q > 0 when mY < mx) the incident projectile must supply a certain minimum amount of energy (Ex) before the reaction can occur. This minimum incident energy is termed the total reaction threshold energy. Two types of reaction threshold energies are encountered. These are kinetic threshold energy or briefly threshold energy (Ethr), and Coulomb barrier threshold (Ec) [Shultis and Faw, 2002].

 KINETIC THRESHOLD ENERGY:

The kinetic threshold energy (threshold energy) is charge independent i.e. exists for all charged and neutral projectiles. The actual amount of energy required to bring about a nuclear reaction is slightly greater than the Q- value. This is due to the fact that not only energy but also momentum must be conserved in any nuclear reaction. From conservation of momentum, a fraction M /(M +MX) of the kinetic energy of the incident particle a must be retained by the products. This implies that only a fraction MX/(M +MX) of the incident particle is available for the reaction. It follows that the threshold energy is higher than the Q- value and is given by

Chapter One Introduction and Literature Review

 COULOMB BARRIER THRESHOLD:

If the incident projectile (x) is a neutron or gamma photon, it can reach the nucleus of the target without repulsion. The minimum energy needed to initiate a given nuclear reaction is, thus, only that specified by the threshold energy. However, if the incident projectile is a positively charged particle the situation will be different. As it approaches the target nucleus, Coulombic nuclear forces repel the projectile, and, if the projectile does not have sufficient momentum, it cannot reach the target nucleus. Only if the projectile reaches the surface of the target nucleus can nuclear forces cause the two particles to interact and produce a nuclear reaction. Thus, even for a reaction with a positive Q- value, if a positively charged incident projectile does not have enough kinetic energy to reach the target nucleus, the reaction cannot occur even though energy and momentum constraints for the reaction can be satisfied. The Coulombic repulsive potential between the incident projectile (charge Zxe) and the target nucleus (charge ZXe), when separated by a distance (r), is

where ε0 is the permittivity of free space.

However, at contact we may assume, to a first approximation, that 1/3 1/3 r= Rx+RX=R0(Ax +AX ) where (Rx), (RX) are the radii of the incident -13 projectile and the target nucleus, respectively, R0 ≈ 1.25 * 10 cm, and (Ax), (AX) are the nucleon number of the target and the projectile respectively. Thus, for an incident particle with a positively charged nucleus to interact with the target nucleus, it must have a kinetic energy to penetrate the Coulomb barrier of about (after substituting appropriate values for the constants)

 OVERALL THRESHOLD ENERGY:

For a neutral incident particle (e.g., neutron or photon), no Coulomb barrier has to be overcome before the reaction takes place. For exoergic reactions (Q > 0), there is no threshold. For endoergic reactions

Chapter One Introduction and Literature Review (Q < 0), the only threshold is the kinematic threshold energy. However, for incident particles with a charged nucleus, the Coulomb barrier always has to be overcome. For exoergic reactions (Q > 0), there is no kinematic threshold, only the Coulomb barrier threshold Ec is exist. For endoergic reactions (Q < 0), there are both kinematic and Coulomb thresholds.

1.3.3. REACTION CROSS SECTION

A nuclear reaction occurs, when a projectile comes sufficiently close to the target nucleus, i.e. closer than the range of the nuclear forces. In the first sight this means that the reaction probability to occur is approximately stable and equal to the geometrical cross section (πR2) i.e. about 10-24 cm2. This geometrical picture takes no account of the finite size of the incident particle nor does it consider the range of interaction forces that are in effect between the incident particle and the target nucleus. Rather than treating a geometrical cross sectional area (πR2) as a measure of interaction probability, an effective area (ζ) perpendicular to the incident beam were assigned to the nucleus such that a reaction occurs every time a bombarding particle hits any part of the effective disk area. This effective area is referred to as the reaction cross section ζ and is usually measured in barn, where 1 barn = 1 b = 10−24 cm2 [Podgoršak, 2006]. The reaction cross section is a function of not only of the target nucleus, but also of the type and energy of the bombarding particle [Stake, and Mido, 2003]. We associate a cross section with each particular type of nuclear reaction. Thus we speak of a scattering cross section (s) when referring to a nuclear scattering process, an absorption cross section (a) when referring to an absorption process or a fission cross section (f) when dealing with a nuclear fission reaction and so on. We can also concern with the probability to find the outgoing particle at certain angle or certain energy i.e. the angular or energy differential cross section, while the reaction cross section represent the probability of finding it over all energies and all angels [Krane, 1988]. The various possibilities are then represented by the total cross section t which is equal to the sum of all partial cross sections involved. The integral cross section (or production cross section) refers to the sum of cross sections of all reaction channels on a well-defined target nucleus, which lead to direct production of the final nuclide. The same final nuclide can also be produced indirectly via the decay of progenitors produced simultaneously on the target nucleus. In many cases the separation of direct and indirect routes becomes unimportant and one uses the cumulative production

Chapter One Introduction and Literature Review cross-section to describe these two routes together. This becomes even more complicated when one uses a natural multi-isotopic target element where different reaction channels on different target nuclei can contribute to the production of the same final radioisotope. In this case one uses the elemental production cross section to describe all production routes together. It should be noted that in doing so one must properly calculate the number of target nuclei, by summing nuclei of all contributing target isotopes. If one considers also indirect production routes, the elemental cumulative production cross-section should be used. Similarly, the notation isotopic production cross-section is used to describe reactions with mono isotopic target elements [Tárkányi, 2001]. The cross section dependence on the energy is called the excitation function. So the plot of the cross section against the energy represents the excitation function curves. The shape of some excitation functions can be explained with the competing channels as a steep rise near the threshold followed by a plateau and then a decrease at energies, where other reactions become energetically possible. The excitation functions are essential in the field of radioisotope production [Al-Abyad, 2003] for:-

 Determination of the optimal energy ranges required for a particular reaction.

 Calculation of the radioisotope production yield which can be expected for this reaction and a given target.

 Calculation of yields for a possible produced radionuclidic impurities.

Charged particle induced nuclear reaction cross-sections are of great interest for many applications, such as:-

 Radioisotope production, for medical applications, industrial and agricultural use.

 Monitoring the beams energy and current intensity for light charged particles (p, d, 3He, α) available at cyclotrons and electrostatic accelerators.

 Surface analysis in industrial applications.

Chapter One Introduction and Literature Review  Astrophysics and cosmochemistry [Tárkányi, 2001].

1.3.3.1. CROSS SECTION MEASUREMENT

There are two methods commonly used for induced reaction cross section measurement involve, direct (online) detection of the emitted particles x, also known as spectroscopic method or offline identification of the activation products Y, which can take place long after the actual irradiation experiment. In case of a radioactive product the activation method is applied, which was the main technique used in this work.

 Determination of the emitted particle:

This online method involves the measurement of the energy and angular distribution of the emitted particle, thus resulting in double differential cross section data. A thin sample is required for measurements of (n, charged particle) reactions, since the ranges of the emitted particles are rather short. Another drawback is the particle selectivity of this method. It is not easy to distinguish whether, for example, an emitted proton originates from an (n,p) or from an (n,np) reaction.

 Activation method:

Since the activation method involves the measurement of the radioactive product, it is not possible to distinguish an (n,np) reaction from an (n,d) reaction, or if it was produced via several production routes. But in contrast to the online methods it is possible to use a large (thick) sample, which may require further radiochemical processing of the irradiated sample material. The yield of a nuclear reaction can be calculated, when the cross section (ζ) and the beam flux (Φ) are known. On the other side, the cross section can be determined when the flux and the yield are measured [Reimer, 2002]. The most simple activation situation is illustrated by the constant irradiation of some material by a constant spatially uniform flux radiation density that begins at some time t = 0, continues for an irradiation period that ends at t = ti. So, if a homogeneous beam of ionizing radiation with flux (Φ Particle per second per cm2) is allowed to pass through a thin sheet of target material of area (S cm2), thickness (d cm), and having (N) nuclei per cm3, the effective nuclear target area which is available for nuclear reactions to occur is

Chapter One Introduction and Literature Review given by the product of cross section per target nucleus and total number of target nuclei contained in the target sheet [Liverhant, 1960].

We are assuming that the target is thin enough so that no overlapping of nuclei in successive layers occurs that might cause a screening of some nuclei by those in the preceding layers. Thus every nucleus presents an entire effective cross section to the incident radiation. The probability or the chance for one incident particle to hit a nuclear target area is equal to the ratio of this area to the total area (S) presented to the incident particle. Hence

The number of nuclear reactions per second, (R), is obtained from this by multiplying the probability per particle by the total number of particles incident on the target per second. This number is given by the product of beam intensity (flux, denoted by Φ) and the area of incidence (S). Hence,

where (V) is the volume of the target, i.e. (Sd), (N0) is total number of target nuclei i.e. (NV) [Liverhant, 1960]. The number of nuclear reactions per second, (R), is simply the rate at which the new nuclei are formed. When the product nucleus is radioactive, its loss through decay during the irradiation time is (- λ n(t)) where, (n(t)) represents the number of the product nuclei at any time, and (λ) is its decay constant. Thus, the rate of change of the number of new radioactive nuclei is given by [Kaplan, 1963],

The equation has the following solution for 0 < t < ti,

Chapter One Introduction and Literature Review

The activity induced in the material as a function of time during the irradiation is given by

At the instant of completion of irradiation the activity at End Of Bombardment (AEOB) is

The decay period followed the irradiation time is called the "cooling time" and denoted (tc). (tc) is a period which begins at t=ti and ends at t=ti+tc. Hence the activity as a function of the cooling time will obviously decay exponentially and be given by:

which is the so called activation formula.

When performing experiments using the activation method, several parameters are needed to be optimized in order to obtain valuable cross section data. These parameters include the type of the projectile, its incident energy, the irradiation time and the beam intensity. The cross section is determined by measuring the induced activity of the activation product. This is most conveniently done by measuring the (γ) rays, following the (β) decay, via (γ) ray-spectroscopy using HPGe or NaI detectors. In cases were no (γ) rays are emitted the activity has to be determined by (β) counting or X-ray spectroscopy. This usually requires some radiochemical processing of the irradiated sample material. If a metastable state is populated, the isomeric cross section can either be determined by measuring the (γ) rays of the internal transition (IT) leading to the ground state or the (γ) rays succeeding the (β) decay of the metastable state [Reimer, 2002]. While measuring the induced activity one should choose carefully the cooling time, the measuring time and the measuring geometry.

Chapter One Introduction and Literature Review 1.3.3.2. TARGET YIELD

The yield for a target having any thickness can be defined as the ratio of the number of nuclei formed in the nuclear reaction to the number of particles incident on the target. It is termed as the physical yield, (Y), and from its definition it‟s a unit is Becquerel /Coulomb (Bq/c). The analytical meaning of the physical yield is the slope (at the beginning of the irradiation) of the curve of the growing activity of the produced radionuclide versus irradiation time [Podgoršak, 2006; Tárkányi, 2001].

Radioisotopes disintegrate during the bombardment, therefore for practical applications other yield definitions are used taking into account this effect. The activity at the end of a bombardment performed at a constant (1µA) beam current on a target during (1 hour) is closely related to the measured activity in every day isotope production by accelerators, the so called (1h–1µA) yield, and denoted (A1). In practice, this latter quantity can be used when the bombardment time is significantly shorter than or comparable with the half life of the produced isotope.

When the irradiation time is much longer than the half-life of the produced isotope ((1-exp (-λt)) ≈ 1), a saturation of the number of the radioactive nuclei present in the target is reached, and their activity becomes practically independent of the bombardment time (at a constant beam current). This activity produced by a unit number of incident beam particles is the so-called saturation yield, A2.

Because of the relatively slow approach to the saturation (Asat), it is generally accepted that in practice, irradiation times beyond (2t1/2) are not worthwhile [Podgoršak, 2006] (Fig. 1.1). There are close relationships between the above-mentioned yields. Using the decay constant of the radionuclide (λ) and the irradiation time (ti) one gets

Chapter One Introduction and Literature Review

If the irradiation time is too shorter than the half life of the produced isotope the quantity (exp (-λt) ≈ 1-λt) and hence, the growth of the activity will be rapid and almost linear with time.

If the mixture is being irradiated and there are short lived and long lived radionuclides being formed, we take advantage of their difference in the time to saturation. If we want the short lived nuclide(s), we irradiate for a short time because very little of the long lived product will be formed. If we want the long lived nuclide(s), we irradiate for the long time, take the sample out and wait for the short lived ones to decay.

Fig. 1.1 Growth of daughter activity A(t) normalized to saturation activity Asat plotted against time normalized to the half-life of the daughter (t1/2). The slope of the tangent on the A(t)/(Asat) vs. t curve at t = 0, defined as the activation yield (Y), is also shown.

Several other definitions are often used. Differential or thin target yield is defined for negligibly small (unit) energy loss of the incident beam in the thin target material. Thick target yield is defined for a fixed macroscopic energy loss, Ein-Eout, in a thick target. Integral yield is defined for a finite energy loss down to the threshold of the reaction, Ein- Eth. The thin target yield is easily related to the reaction cross-section and the stopping power of the target material for the beam considered see

Chapter One Introduction and Literature Review

[Tárkányi, 2001]. The yield for any target thickness, Ythick can be obtained from the simple formula

Ythick (Ein - Eout) = Y (Ein) – Y (Eout), (1-27) where (Ein) is the incident particle energy and (Eout) is its outgoing energy.

1.3.4. REACTION CHANNELS

For a given particle energy different reactions are possible depending on the Q- values. These reactions are called reaction channels; hence we have exit channels for an entrance channel. The exit channels may be elastic and inelastic scattering, radiative capture, charged particle emission etc. If the energy of the projectile is less than the threshold energy of some endoergic reaction the respective channel is called closed. At very low energies of a projectile, only exoergic channels are open. As the energy rises, the endoergic channels begin to open one after the other.

1.3.5. STOPPING POWER AND RANGE

A charged particle is surrounded by its Coulomb electric force field that interacts with orbital electrons and the nucleus of all atoms it encounters as it penetrates into matter. The energy transfer from the charged particle to matter in each individual atomic interaction is generally small, so that the particle undergoes a large number of interactions before its kinetic energy is spent. Stopping power is the parameter used to describe the gradual loss of energy of the charged particle as it penetrates into an absorbing medium. Stopping powers play an important role in radiation dosimetry. They depend on the properties of the charged particle such as its mass, charge, velocity and energy as well as on the properties of the absorbing medium such as its density and atomic number. As a charged particle travels through an absorber, it experiences Coulomb interactions with the nuclei and the orbital electrons of the absorber atoms. These interactions can be divided into three categories depending on the size of the classical impact parameter (b) compared to the classical atomic radius (a) as in Fig. 1.2:

Chapter One Introduction and Literature Review  Coulomb force interaction of the charged particle with the external nuclear field (bremsstrahlung radiation production) for b << a.

 Coulomb force interaction of the charged particle with orbital electron for b ≈ a (hard collision).

 Coulomb force interaction of the charged particle with orbital electron for b >> a (soft collision).

Fig. 1.2 Collisions of charged particle with an atom, depending on the relative sizes of the impact parameter b and atomic radius a.

The major part of the energy loss is due to atomic electron collision. The rate of energy loss per unit of path length by a charged particle in a medium is called the linear stopping power (dE/dx). It is typically given in units (MeV.cm2.gm-1) and referred to as the mass stopping power (S) and equal to the linear stopping power divided by the density (ρ) of the absorbing medium. The stopping power is a property of the material in which a charged particle propagates [Podgoršak, 2006].

Two types of stopping powers are known:

I. Radiative stopping power that results from charged particle Coulomb interaction with the nuclei of the absorber. Only light charged particles (electrons and positrons) experience appreciable energy losses through these interactions that are usually referred to as bremsstrahlung interactions.

II. Collision (ionization) stopping power that results from charged particle Coulomb interactions with orbital electrons of the absorber.

Chapter One Introduction and Literature Review Both heavy and light charged particles experience these interactions that result in energy transfer from the charged particle to orbital electrons, i.e., excitation and ionization of absorber atoms.

The total stopping power for a charged particle traveling through an absorber is the sum of the radiative and collision stopping power.

The classical mass collision stopping power for a heavy charged particle (Niels Bohr 1913) colliding with orbital electrons is then given with the following approximation:

The non-relativistic quantum-mechanical expression for the mass stopping power of heavy charged particles was derived by Hans Bethe and Felix Bloch to be

Bethe‟s relativistic quantum-mechanical expression for the mass collision stopping power of heavy charged particles accounts for relativistic effects to get

Two corrections were subsequently incorporated into Bethe‟s expression for the mass collision stopping power:

 Correction CK/Z to account for non-participation of bound K-shell electrons in the slowing-down process. This correction reduces the collision stopping power but is only effective at low kinetic energies of the charged particle.

 Polarization (density effect) correction δ also lowers the collision stopping power. It is applied to condensed media (liquids and solids) for which the dipole distortion of the atoms near the track of

Chapter One Introduction and Literature Review the charged particle weakens the Coulomb force field experienced by the more distant atoms, thus decreasing their participation in the slowing down process.

Then Bethe‟s relativistic quantum-mechanical expression results in the following relationship;

where, e Elementary charge v Velocity of the projectile NA Avogadro‟s number c Speed of light A Atomic number of the target I Mean ionization- excitation potential Z Atomic number of the target β Normalized incident material particle velocity = v/c ε0 The permittivity of free space Ck k-shell correction z Atomic number of the projectile δ Density effect correction me Electron mass

From the general expression for the mass collision stopping power, we note that the mass collision stopping power (S) for a heavy charged particle traversing an absorber does not depend on charged particle mass but depends upon:

 Atomic number (Z), atomic mass (A), and mean ionization- excitation potential (I) in the form [(Z/A) and (−ln I)] of the absorber. As (Z) increases, (Z/A) and (−ln I) decrease resulting in a decrease of (S).

 Particle velocity (v). By increasing non-relativistic velocities (S) first increases, reaches a maximum, then decreases as (1/υ2), reaches a broad minimum Fig. 1.3 and then, slowly rises with the relativistic term (ln β2 − ln(1 − β2)− β2) as (υ) becomes relativistic and approaches (c).

 Particle charge (ze). (S) increases as (z2) i.e. a doubly charged particle experiences 4 times the collision stopping power of a

Chapter One Introduction and Literature Review singly charged particle of the same velocity (v) moving through the same absorber [Podgoršak, 2006].

Fig. 1.3 The shape of the collision stopping power curve as a function of the charged particle kinetic energy E.

Due to the energy loss of the ionizing particles when passing through matter, an important question arises, that is, how far will the particles penetrate before they lose all of their energy? This distance of which the charged particle travels before coming to rest is called the range. It depends on the type of material, the particle type and its energy. Due to the statistical nature of interactions and hence the energy loss, two identical particles with the same initial energy will not in general suffer the same number of collisions and hence the same energy loss. Thus the range will not be a well defined number for all identical particles with the same initial energy in the same type of material. Instead, a statistical distribution of ranges centered about some mean value. This phenomenon is known as range straggling. In a first approximation, this distribution is Gaussian in form and the mean value of the distribution is known as the mean range. From a theoretical point of view, the mean range of a particle of a given energy (E) might be calculated from the integration of the reciprocal of the stopping power.

This yields the approximate path length travelled and ignores the effect of multiple Coulomb scattering which causes the particle to follow a zigzag path through the absorber. Thus, the range, defined as the

Chapter One Introduction and Literature Review straight-line thickness, will generally be smaller than the total zigzag path length [Leo, 1992].

1.3.6. NUCLEAR REACTION MECHANISMS

As mentioned before the collisions are classified into two categories: nuclear reactions, and scattering collisions (elastic collisions; and inelastic collisions). In the elastic collisions, the products and the reactants are identical in which;

 The total kinetic energy and momentum before the collision are equal to the total kinetic energy and momentum, respectively, after the collision.

 A small fraction of the initial kinetic energy of the projectile is transferred to the target nucleus, but it is left in the same nuclear state as before the collision [Podgoršak, 2006].

In inelastic scattering, similarly to elastic scattering, the reaction products after collision are somehow identical to the initial products. The incident projectile transfers a portion of its kinetic energy to the target in the form of not only kinetic energy but also in the form of intrinsic excitation energy. The excitation energy may represent:

 Nuclear excitation of the target.

 Atomic excitation or ionization of the target.

 Emission of bremsstrahlung by the projectile.

Nuclear reactions may entail three types of reaction mechanisms: direct, compound nucleus and preequilibrium process. The contribution of these processes depends on the given reaction and the energy of the incident particle. The three types can be distinguished by their angular distributions and time scales. In direct reactions only very few nucleons take part in the reaction, with the remaining nucleons of the target serving as passive spectators. Such reactions might insert or remove a single nucleon from a shell-model state and might therefore serve as way to explore the shell structure of nuclei. The other extreme is the compound nucleus mechanism, in which the incoming and target nuclei

Chapter One Introduction and Literature Review merge briefly for a complete sharing of energy before the outgoing nucleon is ejected, somewhat like evaporation of a molecule from a hot liquid. Between these two extremes are the resonance reactions, in which the incoming particle forms a quasibound state before the outgoing particle is ejected.

1.3.6.1. COMPOUND NUCLEAR REACTIONS

This reaction can be treated as a two step process. In the first step the incident particle stays in the nucleus for a relatively long time (10-15s) compared with the time that would be required for a particle to travel across the nucleus- natural nuclear time- forming a compound nucleus and delivers its energy to many nucleons in the target nucleus, then this energy is rapidly distributed throughout the nucleus. The incident particle itself becomes indistinguishable from other nucleons in the compound nucleus. In the second step the compound nucleus disintegrates by ejecting a particle (proton, neutron, α- particle, etc...) or a - ray, leaving the final or product nucleus. The excitation energy of the compound nucleus is equal to the kinetic energy introduced by the incident particle plus its binding energy. This energy is statistically distributed among the nucleus, and each nucleon is rapidly colliding with the others and changing its energy [Kaplan, 1963]. During the process of energy- momentum sharing more and more degrees of freedom are excited after each interaction with the consequence that the nuclear state becomes more and more complex. After a certain relaxation time a condition of statistical equilibrium is reached when the average number of excited degrees of freedom becomes constant [Singh and Mukherjee, 1996]. At statistical equilibrium it may happen that by chance enough energy is concentrated on one or more nucleons that they can leave the nucleus, and a particle(s) emission takes place, such as molecule evaporation from a hot liquid. This compound nuclear reaction model was proposed first by Bohr in 1936 and denoted by

where (C*) indicates the compound nucleus.

A given compound nucleus may decay in a variety of different ways, and essential to the compound nucleus model of nuclear reactions is the assumption that the relative probability for decay into any specific

Chapter One Introduction and Literature Review set of final products is independent of the means of the formation of the compound nucleus. The decay probability depends only on the total energy given to the system; in fact, the compound nucleus forgets the process of formation and decays governed primarily by statistical rules. Consequently the angular distributions of the compound nuclear reaction are either completely isotropic. As an example the compound nucleus (51Cr) can be formed through several reactions and decay in a variety of ways as in Fig. 1.4.

Fig. 1.4 Formation nuclear reaction of the compound nucleus 51Cr through various entrance channels and decay through various exit channels.

The compound nucleus mechanism works best for low incident energies, where the incident projectile has a small chance of escaping from the nucleus with its identity and most of its energy intact. It also works best for medium weight and heavy nuclei, where the nuclear interior is large enough to absorb the incident energy. The evaporation analogy mentioned above is really quite appropriate. In fact, the more energy we give to the compound nucleus, the more particles are likely to evaporate. For each final state the cross section has the Gaussian-like shape as in Fig. 1.5. The figure shows the cross sections for (α,xn) reactions, where x = 1,2,3,… For each reaction the cross section increases to a maximum and then decreases as the higher energy makes it more likely for an additional neutron to be emitted. In cases in which a heavy ion is the incident particle, large amounts of the angular momentum can be transferred to the compound nucleus [Krane, 1988]. And since the ejectile come out with low energies the residual nucleus is left with comparatively high excitation where the density of nuclear levels is large. So the ejectile spectrum is continuous Fig. 1.6 [Singh and Mukherjee, 1996]. Hence, to extract that angular momentum the compound nucleus favors the formation of high spin nuclides [Montgomery and Porile,

Chapter One Introduction and Literature Review 1969]. So in the case of the production of two isomeric states of any nuclide via compound nuclear mechanism, the formation of the higher spin state will be favorable.

Fig. 1.5 At higher energies, it’s more likely that additional neutrons will evaporate from the compound nucleus.

1.3.6.2. DIRECT REACTIONS

As the energy of the incident particle is increased, its de Broglie wavelength decreases, until it becomes more likely to interact with a nucleon-sized object than with a nucleus-sized object. It is possible to have direct and compound nuclear mechanisms both contribute to a given reaction. Direct interactions are most likely to involve one nucleon or a cluster of nucleons near the surface of the target nucleus. Direct interactions occur very rapidly, in a time of the order of 10-22 s. In any case the projectile interacts with only a small portion of the nucleus with the consequence that the ejectile (the outgoing particle) takes up a substantial part of the projectile momentum. The ejectile energy is then high and the residual nucleus is left at comparatively low excitation where the nuclear states are discrete. The ejectile spectrum is, therefore also discrete Fig. 1.6 [Singh and Mukherjee, 1996]. Therefore the direct reaction mechanism doesn‟t distinguish between low and high spin states of any product nuclide [Montgomery and Porile, 1969]. Since the projectile energy and momentum governs the kinematics of the interactions leading to direct emissions, the ejectile angular distribution is strongly forward peaked than in the case of compound nuclear reactions [Singh and Mukherjee, 1996].

Chapter One Introduction and Literature Review

1.3.6.3. PRECOMPOUND REACTIONS

The direct and compound nuclear reactions taken together can account for the greater part of the nuclear reaction cross sections. However, these are not the only mechanisms by which particle emission can occur in nuclear reactions. Particle emission is also possible while the composite nucleus is proceeding towards statistical equilibrium. Emissions taking place at this region are called preequilibrium or precompound nuclear processes and can be interpreted from Fig. 1.6 which is a schematic plot of the double differential cross section as a function of the ejectile energy for a given angle.

At the high energy end of the spectrum the emitted particle has discrete energies corresponding to the excitation of specific discrete nuclear states. This part of the spectrum is dominated by the direct reaction mechanism. As the ejectile energy decreases the excitation of the residual nucleus increases. Since the level density of the residual nucleus is very large at large excitations, the ejectile spectrum becomes continuous. The broad peak on the low energy side can be accounted for by the compound nucleus theory. This is shown by the broken line in Fig. 1.6. In between these two extremes lies a portion of the continuous ejectile spectrum which can‟t be accounted for either by direct or compound nuclear reaction. This is the region dominated by precompound emissions [Singh and Mukherjee, 1996]. This necessarily implies that the description of these preequilibrium processes must, somehow, contain both the statistical features, dominant in compound reactions, and some coherent effects (e.g. peaking in the forward-angle region) that characterize direct processes [Hussein and Rego, 1983]. As the composite nucleus proceeds towards statistical equilibrium the projectile energy and momentum are shared between more and more nucleons after each successive interaction. In the initial stages when the number of interactions is small the energy available to each degree of freedom is comparatively large. Consequently the particles emitted at these stages will carry more energy than those emitted from the equilibrated compound nucleus. This qualitatively accounts for the high energy tail of the continuous energy spectrum in Fig. 1.6. Also in the initial stages of the precompound process the composite nucleus retains the memory of the projectile direction as a result of which the emission spectrum from these initial stages is preferentially forward peaked as in

Chapter One Introduction and Literature Review the case of direct reactions. However in the later stages, as the number of degrees of freedom increases the memory of the projectile direction gets more and more diffused and the ejectile spectrum tends towards isotropy. This means that though the precompound ejectile shows forward peaking, it also exhibits substantial cross sections in the backward angles as well [Singh and Mukherjee, 1996].

Fig. 1.6 Schematic energy spectrum of particles emitted at a given angle and for a specific residual nucleus as a consequence of a nuclear reaction. The dashed curve represents the compound nuclear contribution. The discrete peaks at the high energy end correspond to direct reaction contribution.

1.4. BASICS OF GAMMA RAY DETECTORS

The types of detectors available for the measurement of radioactivity are numerous, and they may be designed in the gaseous, liquid, or solid state. They will differ not only in their physical state but also in chemistry. The instrumentation and electronic circuitry associated with radiation detectors will also vary. As a result, radiation detectors and the instrumentation associated with detectors will perform with varying efficiencies of radiation detection depending on many factors, including the characteristics of the instrumentation, the types and energies of the radiation, as well as sample properties. The proper selection of a particular radiation detector or method of radioactivity analysis requires a good understanding of the properties of nuclear radiation, the mechanisms of interaction of radiation with matter, half-life, decay schemes, decay abundances, and energies of decay [L’Annunziata, 2003]. In case of the induced nuclear reactions the analysis method being

Chapter One Introduction and Literature Review through detection of the outgoing particles (Offline method) or detection of the radioactivity from only the radioactive products (Activation method) and hence, different detection methods are used. As mentioned before, using the activation method, the cross section is determined by measuring the induced activity of the activation product. This is most conveniently done by measuring the (γ) rays, following the (β) decay, via (γ) ray-spectroscopy using semiconductor detectors (such as HPGe) or scintillation detectors (such as NaI). In cases were no (γ) rays are emitted the activity has to be determined by (β) counting or X-ray spectroscopy. In general, in the measurement of gamma ray energies above several hundred keV, there are only two detector categories of major importance: inorganic scintillators, of which NaI(Tl) is the most popular, and germanium semiconductor detectors. Although there are many other potential factors, the choice in a given application most often revolves about a trade-off between counting efficiency and energy resolution [Knoll, 2000].

1.4.1. SCINTILLATION DETECTORS

The scintillation detectors is undoubtedly one of the most often and widely used particle detection devices in nuclear and particle physics today. It makes use of the fact that certain materials when struck by a nuclear particle or radiation emit a small flash of light, i.e. scintillation. When coupled to an amplifying device such as a photomultiplier, these scintillations can be converted into electrical pulses which can then be analyzed and counted electronically to give information concerning the incident radiation. Probably the earliest example of the use of scintillators for particle detection was the spinthariscope invented by Crookes in 1903. This instrument consisted of a ZnS screen which produced weak scintillations when struck by α-particles. The basic elements of a scintillation detector are sketched below in Fig. 1. 7. Generally, it consists of a scintillating material which is optically coupled to a photomultiplier either directly or via a light guide. As radiation passes through the scintillator, it excites the atoms and molecules making up the scintillator causing light to be emitted. This light is transmitted to the photomultiplier tube (PM or PMT for short) where it is converted into a weak current of photoelectrons which is then further amplified by an electron-multiplier system. The resulting current signal is then analyzed by an electronics system [Singh and Mukherjee, 1996].

Chapter One Introduction and Literature Review

Fig. 1.7 Schematic diagram of a scintillation counter.

The scintillation material may be organic or inorganic, the common scintillation materials are sodium iodide (NaI), cesium iodide (CsI), zink sulfide (ZnS), and lithium iodide (LiI). Sodium iodide activated with thalium, NaI(Tl), is the most popular scintillation material used for gamma ray spectroscopy. The extraordinary success stems from its extremely good light yield, excellent linearity, and the high atomic number of its iodine constituent [Knoll, 2000]. Scintillator like sodium iodide have the advantage of availability in large sizes, which, togeather with the high density of the material, can result in very high interaction probabillities for gamma rays. The relatively high atomic number of iodine also assures that a large fraction of all interactions will result in complete absorption of the gamma ray energy, and therefore the photofraction (or fraction of events lying under the full-energy peak in the pulse hight spectrum) will aso be relatively high. However, one of the major limitations of scintillation counters is their relatively poor energy resolition. The chain of events that must take place in converting the incident radiation energy to light and the subsequent generation of an electrical signal involves many inefficient steps.

1.4.2. SEMICONDUCTOR DETECTOR

Semiconductor detectors, as their name implies, are based on crystalline semiconductor materials, most notably silicon and germanium. While work on crystal detectors was performed as early as the 1930‟s, real development of these instruments first began in the 1950‟s. The first prototypes quickly progressed to working status commercial availability in the 1960‟s. These devices provided the first high resolution detectors for energy measurement and were quickly adopted in nuclear physics research for charged particle detection and gamma spectroscopy [Singh and Mukherjee, 1996]. The basic operating principle of semiconductor detectors is analogous to that in gas ionization

Chapter One Introduction and Literature Review chambers except that a semiconductor crystal instead of a gas fills the space between the anode and cathode. When ionizing radiation is absorbed in the crystal, electron-hole pairs are collected rather than electron-ion pairs [Wernick and Aarsvold, 2004]. Its density is much higher (5.33 gm/cm3 vs. 2 x 10-3 gm/cm3). The energy required to produce an electron-hole pair is 10 times lower than that required to ionize a gas molecule, i.e., 2.96 eV vs. ~30 eV, producing much better statistics and consequently a significantly greater energy resolution. The same analogy can be made for semiconductor and scintillation detectors. Scintillation detectors as mentioned above have relatively poor energy resolution such that good germanium systems will have a typical energy resolution of a few tenths of a percent compared with 5-10% for sodium iodide. Not only does good resolution help separate closely spaced peaks, but it also aids in the detection of weak sources of discrete energies when superimposed on a broad continuum. Detectors with equal efficiency will result in equal areas under the peak, but those with good energy resolution produce a narrow but tall peak that may then rise above the statistical noise of the continuum Fig. 1.8 [Knoll, 2000].

Fig. 1.8 Comparison of NaI(Tl) and HPGe spectra for 99mTc.

Using a p-n junction the depletion region will function as a radiation detector (although with relatively poor performance). When a charged particle passes through a semiconductor, electron-hole pairs are created along the path of the charged particle. These electrons allow for the conduction of electricity. In short, this conduction of electricity allows a pulse to be formed. However, the contact potential is too low to generate electric fields that will move charge carriers quickly. Incomplete charge collection can result, as charges have time to be trapped or

Chapter One Introduction and Literature Review recombine. This means that the noise characteristics of an unbiased junction are poor. Moreover, the thickness of the depletion region is quite small, so that only a small volume of the crystal acts as a radiation detector, which requires extension of the depletion region. The semiconductor detector operates much better as a radiation detector if an external voltage is applied across the junction in the reverse biased direction. Reverse biasing a junction increases the thickness of the depletion region because the potential difference across the junction is enhanced. For a semiconductor detector, the depletion depth is given by,

where (V) is the reverse bias voltage, (є) is the dielectric constant, (e) is the elementary charge, and (N) represents the net impurity concentration in the initial semiconductor material. If silicon or germanium of normal semiconductor purity is employed, the maximum achievable depletion depth is a few mm even at bias voltages close to the breakdown level. Thus, the impurity concentration should be much reduced down to 1010 atoms/cm3 in order to realize intended depletion depths of cm order. At this impurity concentration, a reverse bias voltage of 1 kV can produce a depletion depth of 1 cm [Byun, 2010]. Several techniques have been used for increasing the depletion depth. In High Purity Germanium, or simply HPGe, detectors the crystals are manufactured from ultrapure germanium. The reason that high level of purity in the material is desired has to do with the depletion region. The depletion region is desired to be as large as possible. Thus from the depletion region equation, it follows that, the lower the impurity concentration, the higher the depletion depth is. Due to the small band gap of about 0.7 eV, germanium detectors are impossible to operate at room temperature. This lack of functionality at room temperature stems from the large thermally induced leakage current that result at this temperature. In order to get around this, the germanium detector is cooled to the point where this thermal leakage no longer spoils the excellent energy detections. This temperature happens to be 77 K and is achieved through the use of liquid nitrogen to cool the detector [Rittersdorf, 2007]. The resultant charge is integrated by a charge sensitive preamplifier and converted to a voltage pulse with amplitude proportional to the original photon energy. An amplifier then increases the size of the pulse from the output of the preamplifier. The output of the main amplifier is a peak of nearly Gaussian shape with amplitude proportional to the gamma ray which inters the detector. The Analogue-

Chapter One Introduction and Literature Review Digital Converter (ADC) changes this pulse into digital signal proportional to the pulse height which is then deposited as a count in the appropriate channel number of the analyzer. A typical simple electronic system for gamma ray spectrometry might be as shown in Fig. 1.9.

Fig. 1.9 A simple schematic electronic system for gamma spectrometry.

1.4.3. THE DETECTOR EFFICIENCY

The efficiency (ε) is a measure of the probability (expressed in absolute values or in percent) that a gamma ray of energy (Eγ) is fully absorbed in the active volume of the detector or, in other words, the probability that it contributes to the full-energy peak. It depends basically on the solid angle (Ω) under which the source is seen by the detector and on intrinsic factors characteristic of the detector.

1.4.3.1. ABSOLUTE EFFICIENCY

The absolute efficiency is the ratio between the number of pulses recorded by the detector to the number of radiation quanta emitted by the source.

where N(E) is the net area under the peak at energy (E), (Tl) is the live time of the count, (tr) is the real time of the count, (λ) is the decay constant, (A) is the activity in Bq at the starting time of data acquisition,

Chapter One Introduction and Literature Review

Iγ(E) is the relative gamma intensity at energy (E) (which is equal to ratio of the gamma emission rate at energy (E) to the disintegration rate), and the term represent the decay correction for the decay during the counting period [L’Annunziata, 2003].

1.4.3.2. INTRINSIC EFFICIENCY

Not always are all photons striking the detector volume registered. Therefore another kind of efficiency is used which is called the intrinsic efficiency. It is the ratio of the number of signals recorded by the detector to the number of photons striking the detector. For point source geometries the relation between absolute and intrinsic efficiency is

where (Ω) is the solid angel under which the source sees the detector, (r) is the radius of the detector window, and (R) is the source-detector distance. The intrinsic efficiency of a detector usually depends primarily on the detector material, the radiation energy, and the thickness of the detector in the direction of the incident radiation [Al-Abyad, 2003].

1.4.3.3. RELATIVE EFFICIENCY

Efficiency of one detector relative to another; commonly the ratio of the absolute detector efficiency at 1332.5 keV (60Co) to that of the same gamma ray obtained with a 3 inch×3 inch NaI(Tl) scintillation detector, the point source being placed at 25 cm on the axis of the endcap (measured from the center of the source to the front of the endcap). The relative efficiency can be helpful to construct a very crude absolute efficiency curve when, besides the detector‟s relative efficiency, the diameter of its active volume is also given. The efficiency cited by the manufacturer of a Ge detector following the IEEE standards (ANSI/IEEE Standard 325-1986) represents the relative efficiency [L’Annunziata, 2003].

1.5. LITERATURE REVIEW

A survey of the available cross section data for 3He induced nuclear reactions on natural cadmium showed too rare data. Both [Qaim and

Chapter One Introduction and Literature Review Döhler, 1984] and [Szelecsényi et al., 1991] used natural cadmium foils.

[Qaim and Döhler, 1984] studied the production of 117mSn π - 113 π + (t1/2=13.6 d, J =11/2 ), and Sn (t1/2=115.09 d, J =1/2 ) through the induced reactions 116Cd(3He,2n)117mSn, and 111-114Cd(3He,xn)113Sn respectively. They irradiated natural cadmium for three hours at the compact cyclotron (CV 28) as well as the medium energy isochronous cyclotron (JULIC). The respective incident beam energies were 36 and 120 MeV with about 10 nA beam current. The cross section calculation of 117mSn showed one peak of 1.6 mb at 18 MeV which is clearly low value. The cross section of 113Sn showed the same trend; again one peak but with higher value 379 mb at 33 MeV.

[Szelecsényi et al., 1991] studied the reactions natCd(3He, x) 110Sn π + nat 3 111 π + (T1/2=4.11 h, J =0 ), Cd( He, x) Sn (T1/2=35.3 m, J =7/2 ), and nat 3 113m π + 110 Cd( He, x) Sn (t1/2=21.4 m, J =7/2 ). They aimed to produce In π + 110 (T1/2=4.9 h, J =7 ) via the production of Sn which by positron emission decaying to 110In. They used the MGC-20E cyclotron of ATOMKI, Debrecen to irradiate natural cadmium with 27-16.3 MeV 3He. The excitation functions of 110Sn, 111Sn, and 113mSn showed the same trend; increasing of the cross section up to the end of the energy range. The maxima cross sections were 58, 76, and 148 mb at 26.4 MeV for the 110Sn, 111Sn, and 113mSn respectively.

[Montgomery and Porile, 1969] used highly enriched foils of (97.2 %) 116Cd foils. The targets were irradiated with the 3He and 4He ion beams of the 152 cm cyclotron at Argonne National Laboratory. Irradiations lasted from 3 to 4 hours at beam intensities of 1 µA. The energies of the 3He ions varied between 13 and 33 MeV. Excitation functions and average range measurements reported for the (3He, α) 115m, g π - 115m π + Cd - (T1/2=44.6 d, J =11/2 for Cd) and (T1/2=53.46 h, J =1/2 for 115g 3 117m π - 116 Cd)-, and ( He, 2n) Sn (T1/2=13.6 d, J =11/2 ) reactions of Cd. The isomeric cross section ratios for reactions leading to 115m, gCd are also reported. The maxima cross sections were 16 and 9 mb at 33 MeV for 115gCd and 115mCd formation respectively and 28 mb at 19 MeV for 117mSn formation. From the calculated average ranges and isomeric cross section ratios they concluded that the mechanisms of the (3He,α)115m,gCd, and (3He,2n)117mSn reactions is direct process.

Chapter One Introduction and Literature Review 1.6. AIM OF THE WORK

Radioisotopes are used daily in medical and industrial applications; see 1.2.2. The most important step in each application is the selection of the suitable radionuclide and production route. This process starts from the availability of nuclear and nuclear reaction data. From a theoretical point of view, the experimental nuclear reaction data are used as input parameters for building and developing theoretical nuclear models and codes to understand and predict reaction mechanisms and nuclear properties. Therefore measurements of activation cross section data are very important both for the everyday practice and for the improvement of the nuclear reaction theory. Charged particle activation are usually performed in accelerators mainly cyclotrons. The activation is usually performed by protons and alpha particles while the activation by deuterons and 3He-particles are relatively rare due to economical reasons. Due to increasing importance of the charged particle activation data in medical and industrial applications, the Nuclear Data Section of the IAEA had started a coordination research project for development of a reference charged particle cross section data base. Thus, systematic investigations of charged particle induced nuclear reactions on different materials are in progress in many laboratories for evaluating their potential use in different applications. We followed the methodology that suggested by the IAEA to make the selection of data more authentic. The first step in evaluation of production data is to compile all available data and to draw an excitation function for each reaction. The second step is a critical analysis of the experimental data, considering specially the monitor reaction cross sections and decay data used in the calculation of reaction cross sections. At the end nuclear model calculations are performed and compared to the experimental data.

The main aim of this work was to study the excitation functions of the induced nuclear reactions (3He,xn), (3He,pxn), (3He,2pxn) on natural cadmium up to 27 MeV to produce tin, indium and cadmium radioisotopes. The standard production routes of these isotopes are charged particles activation by protons and deuterons on natural or enriched cadmium or tin targets. The available experimental data are too low; from 18 measured excitation function only 5 reactions have previous experimental data. Almost all the products have already medical and/or industrial applications. The respectively large number of stable cadmium isotopes (106Cd 1.25 %, 108Cd 0.89 %, 110Cd 12.49 %, 111Cd

Chapter One Introduction and Literature Review 12.8 %, 112Cd 24.13 %, 113Cd 12.22 %, 114Cd 28.73 %, 116Cd 7.49 %) is a good occasion to test nuclear reaction models. Three theoretical nuclear reaction models namely ALICE-IPPE, TALYS-1.2 and EMPIRE-03 that based on different theoretical nuclear models, were used to identifying the relative significance of the different reactions contributing to the formation of a given radionuclide. A comparison between theoretical and experimental results was performed and used to test the models. The integral yields were calculated for almost all products from the measured excitation functions. Isomeric cross section ratios as a function of the projectile energy are of fundamental interest for studying the reactions mechanisms and spin dependence of the formation of the isomeric states. The isomeric cross section ratios were calculated for 110m,gIn and 117m,gIn isotopes and compared with the theoretical calculations.

Chapter Two Apparatus and Experimental Techniques

CHAPTER II APPARATUS AND EXPERIMENTAL TECHNIQUES

Chapter Two Apparatus and Experimental Techniques A particle accelerator is a machine that produces a directional energetic stream of electrically charged particles using electromagnetic fields. There are two families of accelerators. The first is linear accelerators (such as, Van de Graaff and Tandem), in which the beam passes through the accelerating fields only once. The second family is circular accelerators (such as, Cyclotron and Betatron) in which the magnetic fields bend the path of the particles so multiple passes are made through the accelerating structures and focusing magnets. Particle accelerators can also classified to electrostatic and oscillating field accelerators depending on the accelerating electric field. Accelerators have great potential for developing industrial and medical applications. By far, most of commercial applications of accelerators are in materials processing (e.g. ceramics, insulators, metals and plastics) and in medicine. The most common accelerator applications include:

 Medical applications, such as diagnosis, treatment of cancer, radiotherapy, medical radioisotopes production, and biomedical research.

 Mineral and oil prospecting, using neutrons produced with small accelerators.

 Charged particle beams for processing semiconductor chips by ion implantation.

 Intense sources of X-rays for sterilization of medical equipment and food products.

 Charged particle beams for materials sciences analysis and radioisotope production.

 Radiocarbon dating.

There are over 15000 accelerators around the world today make an essential contribution to our well-being, and to many products used in daily life. Over 97% of these accelerators are used for dedicated commercial applications. Only a small percentage (a few hundred) is used for scientific research. The best known and one of the most successful devices for acceleration of ions to millions of electron volts

Chapter Two Apparatus and Experimental Techniques is the cyclotron, which was invented by E. O. Lawrence in 1929. The first working model produced 80 KeV protons in 1930. A conventional cyclotron uses resonance radio-frequency (RF) acceleration of charged particles in a uniform DC magnetic field. Cyclotrons continue to be efficient accelerators for radioisotope production. Developments in the accelerator technology have greatly increased the practical beam current in these machines while also improving the overall system reliability. These developments combined with the development of new isotopes for medicine and industry, and a retiring of older machines indicates a strong future for commercial cyclotrons.

2.1. THE CLASSICAL CYCLOTRON

In its simplest form the classical cyclotron (called uniform field cyclotron) Fig. 2.1 is constructed of two hollow evacuated D-shaped metal chambers (referred to as Dees), which are connected to an alternating high voltage source and separated by a small gap. The entire system is placed inside a closed evacuated vessel called the chamber and affected by strong magnetic field perpendicular to the Dees surface. Although the hollow Dees are connected to the source of high voltage, because of the shielding effect of the metallic chamber walls, there is no electric field within the Dees. Consequently, a strong alternating electric field exists only in the gap between the Dees. A source for producing ions called the ion source is placed in the gap between the Dees, and, depending on the sign of the voltage at that time, any ion in the gap is attracted towards one of the Dees. However, the trajectory of the ions is circular because of the bending effect of the magnetic field. Once an ion is inside the Dee, it stops sensing the electric force, but continues in its circular motion because of the presence of the static magnetic field. But after a half circle, when the ion is about to emerge from the Dee, the direction of the voltage can be changed and the ion can be accelerated again before it enters the other Dee. Similarly, when it is about to exit from the second Dee, the applied voltage can again be reversed and the particle accelerated further. If the frequency of the alternating voltage source is just right, then the charged particle can be accelerated continuously and move in ever increasing radial orbits (i.e. spiral path), until it is extracted.

Chapter Two Apparatus and Experimental Techniques

Fig. 2.1 Schematic diagram of a classical cyclotron.

For non-relativistic motion, the frequency appropriate for the alternating voltage can be calculated from the fact that the magnetic force provides the centripetal acceleration for a circular orbit. Thus for a particle of mass (m) and charge (q) accelerated up to velocity (V) in a classical cyclotron of magnetic field strength (B),

where (r) is the radius of the particle path. Hence the angular velocity (ω) is

Therefore the cyclotron frequency (fc) is equal to

Clearly, keeping the acceleration in phase with the particle motion requires that the frequency of the electric field be the same as fc. This

Chapter Two Apparatus and Experimental Techniques frequency is referred to as the cyclotron resonance frequency. This shows that for a particle of constant mass, the frequency does not depend upon the radius of the particle’s orbit. As the beam spirals out, its frequency does not decrease, and it must continue to accelerate, as it is travelling more distance in the same time.

The radius (r) of the particle’s orbit is equal to

where (v) is the velocity of the particle at that orbit. Similarly the radius (r) increased with the velocity of so that the particle will follow a spiral path from the center of Dees to the edge. The maximum energy that a charged particle has when it is extracted at a radius r = R is given by

Therefore, for a given kind of particles, the energy is proportional to (B2R2) [Das and Ferbel, 2003].

As particles approach the speed of light, they acquire additional mass, which destroy synchronization between oscillating acceleration fields and the revolution frequency of particles. This makes a limitation to the maximum beam energy and a modification to the magnetic field or the frequency or both of them during the acceleration is required to overcome this limitation. In the first case (magnetic field modification) the RF driving frequency is left constant while an alternating magnetic field gradient in space but constant in time compensates for the relativistic mass gain of the accelerated particles. This type of cyclotrons is called Azimuthally Varying Field (AVF) cyclotrons. In the second case the magnetic field is constant while RF frequency is varied with the radius to maintain particle synchronization in the relativistic regime. This type is called synchrocyclotrons. In the third case both magnetic field and RF frequency are varied and too much higher energies are reached without any limitation except the cost of the machine. This type of cyclotrons is called synchrotrons. Our cyclotron belongs to the AVF cyclotrons and its type is MGC-20 cyclotron.

Chapter Two Apparatus and Experimental Techniques 2.2. THE AVF CYCLOTRON

AVF cyclotrons generally have magnet poles with wedge-shaped extensions attached at periodic azimuthal positions. These extensions have boundaries that lie along diameter of the poles or have a spiral shapes Fig. 2.2. The raised regions are called hills and the recessed regions are called valleys. The magnitude of the vertical magnetic field is approximately inversely proportional to the gap width; therefore the field is stronger in hill regions. So a particle in an orbit moves in a magnetic field that is alternately higher and lower than the average magnetic field. An element of field periodicity along a particle orbit is called a sector. So a sector contains one hill and one valley. The periodicity of hill and valley regions along particle orbit produces extra horizontal field components that enhance vertical focusing. The stronger vertical focusing allows higher beam intensities and currents. Therefore AVF cyclotrons are often referred as sector-focusing machines. The name isochronous is also often used [Stanley Humphries, 1986].

Fig. 2.2 Magnetic pole of AVF cyclotron with and without spiral angels.

2.3. IRRADIATION BY THE MGC-20E CYCLOTRON

The irradiation has been done in the MGC-20E cyclotron in Debrecen Hungary. There is a similar MGC-20 cyclotron in Inshas, Egypt. The MGC-20 is a variable energy compact sector-focusing

Chapter Two Apparatus and Experimental Techniques cyclotron intended for acceleration of light ions. The energy range of the cyclotron is equal to

where (z) is the charge number and (A) is the mass number of the accelerated ion.

The MGC-20 cyclotron is a multipurpose facility aiming to use nuclear knowledge based on charged particle accelerators in the field of basic science and applications. The MGC-20 is mostly applied for research in nuclear physics, activation analysis and for production of radionuclides. The energy and current parameters of the MGC-20 cyclotron are mentioned in Table 2.1. The present work used 3He ions with primary energy of 27 MeV. The irradiation time was one hour with a beam current of 100 nA.

Table. 2.1 Energy and current ranges in MGC-20 cyclotron.

Inner beam Extracted beam Particles Energy Current Energy Current (MeV) (μA) (MeV) (μA) Protons 2-20 200 5-18 50 Deuterons 1-11 200 3-10 50 3He++ 4-27 50 8-24 25 4He++ 2-22 50 6-20 25

The MGC-20 cyclotron consists of the following components, Figs. 2.3, 2.4.

A). The components of the cyclotron itself,

1) Magnet.

2) Accelerating chamber.

3) Resonance system.

B). The additional components,

Chapter Two Apparatus and Experimental Techniques

4) Ion source.

5) Gas supply system of the ion source.

6) Vacuum system.

7) Cooling system.

8) Beam extraction system.

9) Beam monitoring and diagnostics

10) Beam transport system.

Fig. 2.3 Schematic diagram of the MGC-20 cyclotron.

Following is some specifications of these components [Galchuk, 1995]

2.3.1. MAGNET

The electromagnet of the MGC-20 cyclotron is an H-shaped magnet consists of three spiral (weakly helical) sectors on each pole. The maximum average magnetic field is 1.6 Tesla. The magnet pole

Chapter Two Apparatus and Experimental Techniques diameter is 103 cm and the extraction radius is 45 cm. The magnetic field is tuned by five concentric coils (four on the top and one on the bottom) for correction of the average field shape. There are two sets of harmonic coils situated in the valleys for correction of lower harmonics of azimuthal non-uniformity of the magnetic field in the central area and at the final radius. The power supply of the magnet is 30 kW.

Fig. 2.4 The Hungarian MGC-20 cyclotron.

2.3.2. ACCELERATING CHAMBER

It consists of upper and lower covers similar in design and casing (of non-magnetic steel). Sections, forming the magnetic field, are located in the vacuum volume of the chamber and are covered with a copper cladding. The chamber cladding is connected with that of the resonance system tank via special mechanical contacts.

2.3.3. RESONANCE SYSTEM

The accelerating system of cyclotron is designed for creation of an accelerating electric field of a specified amplitude and frequency.

Chapter Two Apparatus and Experimental Techniques The accelerating system consists of two ¼ wave resonators each comprising sections of transmitting lines. The resonators are capacitively coupled and excited in opposite phases. The range of frequency tuning in each resonator is 8 - 24 MHz. Resonators are equipped with panels and cladding (capacitors) providing variation of the operating frequency over a required range. The accelerator system also comprises trimmers and sensors for automatic tuning the resonator frequency over small limits and for measuring amplitude and phase of RF oscillations. The dee aperture is chosen taking into account the amplitude of the beam vertical oscillations. The outer conductor consists of a tank, pole cladding, and a transition system, which is the chamber cladding. Dees, panels, and claddings are connected through the dee stem. The RF power supply system includes a pilot generator (frequency synthesizer) of the MGC-20 cyclotron and several amplification stages.

2.3.4. ION SOURCE

The ion source type in the MGC-20 cyclotron is a BIG Livingston hot filament cathode. It is a slit-type closed source with filament cathode (the filament is U- shaped and made of tantalum 2.5 mm in diameter), which is heated with a DC current up to 300 A, 4V. Negative potential up to 500V is applied to the filament. The ion source comprises two main parts the head and the holder connected to each other. The head can be easily removed from the cyclotron chamber without losing the vacuum. The filament cathode is located on the end of the head. The body of the head represents the anode and is earthed while, the filament represents the cathode. The holder cannot be removed from the chamber without losing the vacuum. Anticathode is made of molybdenum to receive the scattered electrons from the filament and reflect them again to the plasma region. The anticathode is isolated from the anode. The MGC-20 cyclotron ion source has a discharge power up to 600 W that allowed producing beams of p & d with intensity over 1000 μA, double-charged ions of 3He++ and 4He++ with intensity above 200 μA.

Chapter Two Apparatus and Experimental Techniques 2.3.5. GAS SUPPLY SYSTEM OF THE ION SOURCE

It supplies the gas to the ion source to be ionized and accelerated. It is a simple system which allows the ion source gas to be pressurized through a copper tube and a simple dosage valve to control the amount of gas.

2.3.6. VACUUM SYSTEM

The total vacuum volume includes the acceleration chamber and the ion beam transport lines is ≈ 3 m3. The vacuum in the cyclotron chamber with no gas supply to the ion source is a usually equal to (3- 5)x10-6 mm Hg and ~ 2x10-5 mm Hg with gas supplied through the ion source. The pumps that used in vacuum system are;

 Forevacuum and bypass pumps: Forevacuum pumping is used for the production of preliminary rarefaction at the high-vacuum diffusion pumps outlets while bypass pumping is used for the production of rough vacuum in the chamber and the beam lines. Two mechanical rotary pumps are used for these purposes.

 High vacuum diffusion pumps: High-vacuum pumping of the cyclotron chamber down to the working pressure is realized by three oil diffusion pumps while the three beam transport lines are evacuated to the working pressure with another three smaller oil diffusion pumps.

There are also a number of pressure valves and meters for control and measure the vacuum.

2.3.7. WATER COOLING SYSTEM

Cyclotron different parts are cooled with closed cycle of distilled water. Three chillers system is used for cooling all parts of the machine and another small chiller is used as secondary part for cooling the diffusion pumps.

Chapter Two Apparatus and Experimental Techniques 2.3.8. BEAM EXTRACTION SYSTEM

The extraction system consists of:

 Electrostatic deflector: The deflector is located between the dees, such that the input of the deflector is located in the hill area, while the output in the valleys area. The maximum voltage at the potential plate is (-45 kV). The electric field strength is 100 kV /cm. The beam enters the deflector with the radius R=450 mm.

 Magnetic channel: The deflected beam enters the magnetic channel which located at an angle of 90° from the deflector in the fringing field. To form the field, gradient shims are used.

2.3.9. BEAM MONITORING AND DIAGNOSTICS

The beam monitoring and diagnostic devices included on the cyclotron are:

 Internal prop: It is located on the chamber on the opposite side to the resonance system. It used for measurements of beam parameters starting from the radius of 130 mm. The head of the probe is made of copper and cooled with water.

 External prop: It located on the beam line just before the switching magnet. It contains five small electrodes to measure the beam spread.

 Beam profile monitor: It used to analyze the beam quality and spatial power distribution Fig. 2.5.

 Faraday cup: It used to collect and measure the current of charged ions in the beam.

Chapter Two Apparatus and Experimental Techniques

Fig. 2.5 Proton beam profile.

2.3.10. BEAM TRANSPORT SYSTEM

The beam transport system is intended to provide distant targets with extracted cyclotron beam. It consists of:

 Vacuum ion guide: pipes made of aluminum alloy equipped with collectors where targets, diagnostics, vacuum pumps, valves, and vacuum gauge heads to be mounted.

 Electromagnet units: Such as the switching magnet (That provides the external beam transportation to different target stations with as low beam losses as possible), quadruple lens doublets (For focusing the beam on targets), and magnetic correctors (For beam positioning in ion guide).

The beam transport system is serve three irradiation units. The first irradiation unit is used for isotope production and nuclear physics experiments. The second unit is mainly used for nuclear physics research, and, the last unit is used for neutron production. The irradiation unit consists of the following well-separated subsystems: vacuum system, cooling system, beam transport and diagnostic system, target positioning and handling system, pneumatic system, production

Chapter Two Apparatus and Experimental Techniques chambers, transporter container and slide-way, and control system Fig. 2.6.

Fig. 2.6 Hungarian beam transport Line.

Besides a control system is used for acquisition and display of the data on the MGC-20 cyclotron and other constituent systems. One personal and three industrial computers are used to control these data.

3 2.4. IRRADIATION BY He

As mentioned, the irradiation has been done in the MGC-20E cyclotron with 27 MeV 3He. This projectile is a light nonradioactive isotope of helium with two protons and one neutron. It is rare on earth; its abundance is 0.0001373 %, so it is manufactured instead of recovered from natural deposits. It can be produced from the decay of tritium and from the D-D nuclear reaction. The high cost of 3He gas is a disadvantage which can be partially solved by using 3He recovery system to get back some of the used 3He gas. Due to the lower atomic mass of 3He (3.0160293191 amu), it has significantly different

Chapter Two Apparatus and Experimental Techniques properties from 4He (4.00260325415 amu). It boils at 3.19 Kelvin compared to 4He’s 4.23 Kelvin, and its critical point is also lower at 3.35 Kelvin, compared to 4He’s 5.19 Kelvin. It has less than half the density when liquid at its boiling point: 0.059 g/ml compared to 4He’s 0.12473 g/ml at one atmosphere. The low binding energy per nucleon for 3He (2.5727 MeV) compared to that for 4He (7.073915 MeV) make it one of the loosely bound projectiles like deuterons and tritons. This means that contributions from transfer and pick up reactions affect the cross section of 3He induced nuclear reactions. Therefore nucleon and cluster emission is possible.

2.5. STACKED-FOIL TECHNIQUE

In applied nuclear physics the cross section measurement of a nuclear reaction is in most cases done by stacked-foil technique Fig. 2.7 (by means of offline gamma ray spectroscopy). In this method several targets (usually thin foils) are placed behind each other and they are irradiated in one step. Thus, single and simultaneous bombardment can be done for several thin targets or special combination of target materials resulting in a series of data point in one irradiation. The simultaneous irradiation of the stack (the set of stacked foils) is not only economical but also could assure a good relative accuracy. The energy degradation of the entering particle beam along the stack is usually determined using the stopping power formula and tables of stopping power and range. The energy value related to the cross section is the mean value of the particle energies at entering and leaving the given foil (taking into account the change of the excitation function). A disadvantage of this technique is that the beam intensity may change along the stack due to scattering and/or focusing of the bombarding particles. Avoiding this problem can be done with proper experimental setup and using low beam current during the activation. Another disadvantage of this technique is that the energy cannot be estimated properly in the stack due to the errors in thickness of the foils, stopping power calculation, and estimation of incident particle energy. To decrease the influence of these errors, one has to decrease the number of foils in the stack and/or use the so called monitor foils.

In all cases the stack thickness must be such that it stopped the beam. The number of foils is determined by taking into account the

Chapter Two Apparatus and Experimental Techniques energy range of interest, the stopping power of the target material, the acceptance level of energy uncertainty and the available irradiation time. In special cases energy degrader foils are placed in the stack. Their purpose is to enhance the energy degradation in the stack, where otherwise a large number of target foils would have been necessary to cover the whole energy region. During nuclear reactions, the newly formed nucleus will recoil by transfer of kinetic energy from the incident particle. As a result the nuclei formed near to the surface will be able to escape from the sample. These recoiled and escaped nuclei can be implanted into the next foil in the stack modifying the activity of the foils. To overcome this problem extra foils called catcher foils have to be included in the stack for every target foil. These foils will catch the escaping recoiled nuclei and then it can be measured separately or together with the target foils and a correction can be made for the recoiled nuclei [Al-Abyad, 2003].

Fig. 2.7 Schematic arrangement for target and monitor stacked-foils.

2.6. TARGET PREPARATION

In order to obtain a large number of cross section data points over a given energy range one should use a large number of target foils. But, to avoid the excessive energy degradation in each foil, it is essential to use thin foils. On the other hand, the foils should be thick enough to produce measurable activities for getting good counting statistics. The principal difference between thin foil and thick foil is not the actual thickness of the foil, but rather how the particles in the beam will see the foil. A thin target is one in which all the target nuclei see the same incident particle flux at the same energy. As the interaction probability increases the target becomes thicker. A thick target could therefore be

Chapter Two Apparatus and Experimental Techniques physically thin but be considered thick from a radiation physics point of view because its interaction cross section is large. In this case, nuclei on the exit side of the target see either a smaller particle flux or a lower energy than the entry side [Smith, 2000]. One can prepare thin targets on several ways. The most frequently used methods are: use of thin films or foils, electrodeposition, evaporation or sedimentation of the target material on thin backing and use of target material in gas form. Typically target foils are cut out of a larger sheet of the appropriate material with known purity and certified thickness. (In most cases we used Goodfellow materials). The thickness of the foils (in mg/cm2) is checked by calculating the surface area and determining the weight of the foils.

The beam energy and intensity in activation technique should be known accurately at every time during irradiation and at every foil i.e. as a function of time and penetration depth. Several methods had been developed for measuring intensity of charged particle beam such as: beam current transformers, calorimetric methods and collecting charge in a faraday cup. Also several techniques had been used for measuring the energy of the bombarding beam such as: Rutherford back scattering, magnetic spectrometers, range-energy functions, calibrated analyzing magnets, measurement of spatial separation between neighboring bunches of particles in the beam and Time Of Flight (TOF). All these methods are technically more sophisticated and need more expertise in applications. The use of monitor reaction is a simple method to determine the flux, provide a check of the calculated particle energy incident at a thin foil and assure the necessary precision needed in different application. From the activity induced by the beam and from the known excitation function of the reaction takes place in the monitor foil, the energy and the intensity of the bombarding beam can be calculated. If the beam parameters were established using monitor reactions, one can actually obtain a relative cross section values. These values are as good as the cross section values of the used monitor reactions. Some criteria are necessary in choosing monitor foils and monitor reactions:

 The target element(s) should be isotopically pure.

 The absolute cross section should be high and known precisely in wide energy range for the incident particle.

Chapter Two Apparatus and Experimental Techniques

 The excitation function should change smoothly as the beam energy increases.

 The half life of the reaction product(s) should be comparable to irradiation time.

 The monitor foils should be available commercially.

 The monitor foils should be stable during activation i.e. having good thermal and electrical properties.

 The reaction product(s) should remain in the foil during and after the irradiation.

 The activity of the reaction product(s) should be accurate and easy to determine.

The above mentioned requirements give a serious limitation for the number of materials having the right properties to be used as beam monitor materials. In the present work high purity natural cadmium 99.5 % supplied by Goodfellow, England were used as a target foils. The monitor foils material used were high purity natural titanium 99.5 % (supplied by Goodfellow, England) which is recommended by the International Atomic Energy Agency IAEA for 3He ions interactions [Tárkányi, 2001]. The stack consists of 11 natural cadmium foils of thickness 15 μm and surface area 1 cm2 as a target placed together with 9 natural titanium thin foils of thickness 4 μm and surface area 1 cm2 as a monitor foils. The sequence of all the target and monitor foils in the stack was produced via a special program called STACK and based on the stopping power and range calculations [Williamson et al., 1966], [Ziegler, 1980]. The monitor foils also served to degrade the projectile energy as well as to calculate the actual beam energy and current during the irradiation. In addition the initial beam parameters; incident energy and particle flux were derived from the accelerator setting and from the integrated charge, measured on the Faraday cup. These parameters were adapted by evaluating the excitation function of the monitor reactions. For this purpose, the IAEA recommended cross section data of the natTi(3He,x)48V reaction were used and a good agreement between our values and that for the recommended values was observed.

Chapter Two Apparatus and Experimental Techniques

2.7. ACTIVITY MEASUREMENT

The induced activity of the irradiated target and monitor foils are usually measured via high resolution gamma ray spectrometry systems. The most common detector used is the High Purity Germanium HPGe with a classical setup (detector, preamplifier, amplifier, Analog to Digital Converter ADC and Multi Channel Analyzer MCA) see 1.4.2. A cross section of a typical HPGe detector with the liquid nitrogen cryostat is shown in Fig. 2.9. The system of measurements in this work at Debrecen Hungary is consists of a CANBERRA HPGe detector with CANBERRA and TENNELEC electronics, and a PC-based CANBERRA MCA placed in a low-background target room. A live photo of that system is in Fig. 2.10. The detector is carefully calibrated in energy scale and counting efficiency using standard gamma sources. The sharp peaks in the HPGe spectra, coupled with a careful precise energy calibration, can be used for generally unique determinations of the nuclides in a sample. All CANBERA HPGe computer-based gamma spectroscopy systems provide nuclide identification through peak searches of spectra and scans of standard and user-generated nuclide libraries.

Fig. 2.8 Cross section of a typical HPGe detector.

Chapter Two Apparatus and Experimental Techniques The net area of any peak is directly related to the intensity of the radioactivity corresponding to an isotope, but it is also necessary to correct for the efficiency of the detector, the branching ratio of the source, and the half life. Measurements are always carried out with the live time correction to correct the dead time of the detector setup. The dead time has to be kept fewer than 5 % for the present measurements. To determine a reaction cross section in stacked foil technique, one has to measure many samples having too high or too low activity and hence, has to know the sequence of the foils in the stack. This done by labeling the target foils and monitor foils separately. In the present work the counting time was adjusted according to the half-life of the product nuclides to get reasonable counting statistics.

Without chemical processing the foils were measured four times. Two measurements have been done in the same day of irradiation starting from less than one hour after the End Of Bombardment EOB in order not to lose the short lived isotopes. The third measurement have been started in the next day while, the fourth measurement have been started more than two weeks later allowing short lived nuclides to decay completely. So, in case of contribution from several isotopes to a single gamma line, one can separate the contributions of the different nuclides. For the same reason, measurements of the monitor foils have been performed 10 days after the EOB. All the major gamma lines of the resulting radionuclides were identified. The peak area analyses were done by using a flexible gamma spectrum analyses program FGM [Székely, 1985].

Fig. 2.9 Live photo of the HPGe detector and the system of data acquisition.

Chapter Two Apparatus and Experimental Techniques

As mentioned above the detector efficiency was determined experimentally using standard gamma sources (152Eu and 111Ba). The source to detector distance was 12 cm. The efficiency was calculated using the various gamma lines in the standard sources through equation 1-35 and fitted by the program TableCurve 2D-V4. Figure 3.11 shows the calculated absolute efficiency and the fitting curve. The fitting equation as obtained from the program is

where E is the gamma energy in KeV and the parameters values are

a = - 0.026475391 b = - 0.000000511 c = 0.000180634 d = 0.133494507 e = - 0.132559964

Fig. 2.10 The efficiency curve of the detector at 12 cm source to detector distance.

Chapter Three Theoretical Calculations

CHAPTER III THEORETICAL CALCULATIONS

Chapter Three Theoretical Calculations Nuclear model calculations are an integral part of modern nuclear data evaluation methodology [Herman, 2001]. Creation of a reference charged particle cross section database for medical radioisotope production requires the evaluation of both experimental and theoretical cross sections for beam monitor reactions and for radionuclide production reactions. For a better understanding of the experimental data it is instructive and advantageous to perform nuclear model calculations and compare the experimental and calculated data [Tárkányi, 2001]. Nuclear model codes are helpful in the validation of existing data; they can also generate an evaluation that is entirely complete in its description of reaction channels, incident and outgoing particle energies and angles. The adjustable parameters of the nuclear model code should be fitted to reproduce the experimental data in the process of evaluation [Koning and Duijvestijn, 2006]. The most important parameters are: optical model parameters, level density parameters, gamma ray transmission coefficients, equilibrated emissions, direct interactions, pre-equilibrium reactions and multiple emissions of particles. The developed models are checked with experimental data to see the extent how much they can reproduce these data. In general it was found that the nuclear model calculations could reproduce the excitation functions reliably only for the simple reaction channels like (p,n), (p,2n), etc. on medium and heavy mass nuclei. In most of the other cases, therefore, heavy reliance was placed on the data fitting methods [Tárkányi, 2001]. In this work analysis of reaction cross section as a function of energy (the excitation function) have been done using three theoretical codes namely; ALICE- IPPE, TALYS 1.2, and EMPIRE-3. The theoretical results are compared with the experimental data obtained in this work. The ALICE-IPPE code [Dityuk et al., 1998] is an update version of ALICE-91 [Blann, 1991] updated by the Obninsk group. The ALICE family of codes is based on the hybrid, the Geometry-Dependent Hybrid (GDH) or the HMS (Hybrid Monte-Carlo Simulation) pre-equilibrium models and the Weisskopf- Ewing evaporation formalism. Among the most reputable codes, TALYS [Koning et al., 2005], and EMPIRE [Herman et al., 2007] which, are the most modern codes are prominent. They have been extensively and very successfully used over the last years, especially in evaluation of neutron data up to 20 MeV. These codes are good choices if one needs to have information on each channel participating in the reaction process, and when the exciton energy (and the number of open channels) is not too large. A comprehensive description of ALICE-IPPE, TALYS-1.2 and EMPIRE-3, the three codes used in this work, is given below.

Chapter Three Theoretical Calculations

3.1. ALICE-IPPE

The well known computer code ALICE was developed by [Blann, 1975] based on the hybrid, geometry-dependent hybrid (GDH) or the hybrid multi-step HMS pre-equilibrium models and the Weisskopf- Ewing evaporation description of equilibrium processes. The Russian group in Obninsk introduced a new version of the code ALICE-91 (ALICE-IPPE) to include the pre-equilibrium cluster emission and the generalized- superfluid-model description of nuclear level densities. This version is used for the creation of Medium Energy Nuclear Data Library, MENDL-2, to study activation and transmutation of materials irradiated with nucleons of intermediate energies and for other applications.

The main features of the ALICE-IPPE code are given below [Dityuk et al., 1998; Hussain, 2009].

1. The calculation of level density for all nuclei in the evaporation cascade used the phenomenological approach [Ignatyuk, 1975; Blokhin et al., 1985] that based on the generalized superfluid model developed in the Institute for Physics and Power Engineering (IPPE).

2. Preequilibrium nucleon spectra are obtained using the geometry dependent hybrid exciton model (GDH) [Blann, 1972; Blann and Vonach, 1983].

3. Preequilibrium cluster emission calculation was included in the code.

4. The calculations of deuteron precompound spectra were carried out in the frame of the exciton coalescence pick-up model combined with hybrid exciton model. The direct mechanism of deuteron emission was also taken into account using phenomenological approach.

5. The spectrum of a-particles is represented as a sum of three components pick-up, knock-out and evaporation processes.

Chapter Three Theoretical Calculations 6. To describe pick-up reaction the Iwamoto-Harada model is used [Iwamoto and Harada, 1982].

7. The modified approach [Milazzo-Colli and Braga-Marcazzan, 1973] for a particle knock-out process description is used.

8. The triton and 3He emission spectra are calculated according to the coalescence pick-up model of Sato, Iwamoto and Harada [Sato et al., 1983].

9. Correction has been made in the cross section calculation taking account of gamma emission from the residual nucleus.

10. Double precision calculations are used in all code.

11. The optical potential parameters for the heavy nuclei have been corrected to achieve agreement of the calculational results with the evaluated data (given in BROND-2, ENDF/B-VI and JENDL-3) and experimental data.

12. Some corrections have been made in the calculations on spectra of the second preequilibrium particle.

13. Correction has been made in the radiation width determination.

The cross-sections were calculated using the recommended input dataset: experimental masses, normal pairing shift (zero for odd–even nuclei, delta added to excitation for odd–odd nuclei, etc.), level density of Ignatyuk model, A/9.0 level density parameter, 0.24 MeV energy bin mesh size, Sierk’s rotating finite range barriers [Sierk, 1986], neutron, proton, alpha and deuteron emission and optical model for inverse cross- sections.

The lake of angular momentum and parity treatments in the Weisskopf-Ewing formalism used in ALICE-IPPE makes independent treatment of isomeric states impossible, thus, only the total production cross section (σg+σm)of the interested channel can be calculated. In the present work 3He induced nuclear reactions on each stable isotope of natural cadmium have been reproduced using ALICE-IPPE. The total cross section of a given isotope was obtained by weighting and summing

Chapter Three Theoretical Calculations the individual results of the reactions producing this isotope according to the abundance of the target isotopes.

3.2. TALYS-1.2

TALYS is a nuclear reaction program created at Nuclear Research and Consultancy Group (NRG), Petten, the Netherlands and CEA Bruyères-le-Châtel, France. It wrote to provide a complete and accurate simulation of nuclear reactions in the 1 keV-200 MeV energy range, through an optimal combination of reliable nuclear models, flexibility and user-friendliness. It can be used for target mass numbers between 12 and 339 and treats n, γ, p, 2d, 3t, 3He, and α as projectiles and ejectiles. TALYS incorporates modern nuclear models for the optical model, level densities, direct reactions, compound reactions, pre-equilibrium reactions, fission reactions, and a large nuclear structure database. It calculates total and partial cross sections, energy spectrum angular distributions, double-differential spectra, residual production cross sections and recoils. There are two main purposes of TALYS, which are strongly connected. First, it is a nuclear physics tool that can be used for the analysis of nuclear reaction experiments. After the nuclear physics stage comes the second function of TALYS, namely as a nuclear data tool: Either in a default mode, when no measurements are available, or after fine-tuning the adjustable parameters of the various reaction models using available experimental data, TALYS can generate nuclear data for all open reaction channels. The nuclear data libraries that are constructed with these calculated and experimental results provide essential information for existing and new nuclear technologies. Important applications that rely directly or indirectly on data generated by nuclear reaction simulation codes like TALYS are: conventional and innovative nuclear power reactors (GEN-IV), transmutation of radioactive waste, fusion reactors, accelerator applications, homeland security, medical isotope production, radiotherapy, single event upsets in microprocessors, oil-well logging, geophysics and astrophysics [Koning et al., 2009].

The specific features of the TALYS package are:

1. In general, an exact implementation of many of the latest nuclear models for direct, compound, pre-equilibrium and fission reactions.

Chapter Three Theoretical Calculations 2. A continuous, smooth description of reaction mechanisms over a wide energy range (0.001- 200 MeV) and mass number range (12 < A < 339).

3. Completely integrated optical model and coupled-channels calculations by the ECIS-94 code [Raynal, 1994].

4. Incorporation of recent optical model parameterizations for many nuclei, both phenomenological (optionally including dispersion relations) and microscopical.

5. Total and partial cross sections, energy spectra, angular distributions, double-differential spectra and recoils.

6. Discrete and continuum photon production cross sections.

7. Excitation functions for residual nuclide production, including isomeric cross sections.

8. An exact modeling of exclusive channel cross sections, e.g. (n,2np), spectra, and recoils.

9. Automatic reference to nuclear structure parameters as masses, discrete levels, resonances, level density parameters, deformation parameters, fission barrier and gamma-ray parameters, generally from the IAEA Reference Input Parameter Library [Capote et al., 2009].

10. Various width fluctuation models for binary compound reactions and, at higher energies, multiple Hauser-Feshbach emission until all reaction channels are closed.

11. Various phenomenological and microscopic level density models.

12. Various fission models to predict cross sections and fission fragment and product yields.

13. Models for pre-equilibrium reactions, and multiple pre-equilibrium reactions up to any order.

Chapter Three Theoretical Calculations 14. Astrophysical reaction rates using Maxwellian averaging.

15. Option to start with an excitation energy distribution instead of a projectile-target combination, helpful for coupling TALYS with intranuclear cascade codes or fission fragment studies.

16. Use of systematics if an adequate theory for a particular reaction mechanism is not yet available or implemented, or simply as a predictive alternative for more physical nuclear models.

17. Automatic generation of nuclear data in Evaluated Nuclear Data File (ENDF-6) format.

18. A transparent source program.

19. Input/output communication that is easy to use and understand.

Fig. 3.1 gives an overview of the nuclear models that are included in TALYS i.e. flowchart of TALYS. All nuclear models make use of structure and model parameters. There is an automatic reference to parameters as masses, resonances, etc. With a few exceptions, TALYS database is based on the Reference Input Parameter Library [Capote et al., 2009].

The coupled-channels code ECIS-94 [Raynal, 1994] used in TALYS as a subroutine for all optical model and direct reaction calculations. The default Optical Model Potentials (OMPs), used in TALYS, are the local and global parameterizations for neutrons and protons of [Koning and Delaroche, 2003]. For nuclides outside the scope of this OMP, i.e. strongly deformed nuclides, TALYS allows input of potentials on an individual basis. With this, coupled-channels calculations for various types of deformation (symmetric-rotational, harmonic-vibrational, vibration-rotational, and asymmetric-rotational) can be automatically performed. For near-spherical nuclides, direct reactions are calculated with Distorted Wave Born Approximation (DWBA), and inelastic scattering of odd-A nuclei is described by the weak-coupling model. For deuteron, triton, 3He and alpha OMPs, TALYS uses a folding approach applied on the aforementioned OMPs. For energies above a few MeV, pre-equilibrium reactions play an important role. For nucleon reactions, TALYS implemented a two-

Chapter Three Theoretical Calculations component exciton model with a new form for the internal transition rates based on the OMP of [Koning and Delaroche, 2003] which yields an improved description of pre-equilibrium processes over the whole energy range [Koning and Duijvestijn, 2004]. Another feature necessary to cover a large energy range is the generalization of multiple preequilibrium processes up to any order of particle emission. This is accomplished by keeping track of all successive particle-hole excitations of either proton or neutron type; see [Koning and Duijvestijn, 2004] for the mathematical outline. Preequilibrium photon emission is taken into account with the model of [Akkermans and Gruppelaar, 1985]. For pre-equilibrium reactions involving deuterons up to alpha particles, a (too low) contribution is automatically calculated within the exciton model reaction equations. TALYS include a phenomenological contribution developed by [Kalbach, 2005] for nuclear reactions involving projectiles and ejectiles with different particle numbers, i.e. mechanisms like stripping, pick-up and knock-out and these direct-like reactions. However, the (very) phenomenological nature of the model still provides a challenge to construct a more physical approach for these reactions in the future. The equilibrium particle emission is calculated with the Hauser-Feshbach formalism including Width Fluctuation Corrections (WFC). The WFC factor accounts for the correlations that exist between the incident and outgoing waves [Koning et al., 2005]. Several models for the level density used in TALYS, which range from phenomenological analytical expressions to tabulated level densities derived from microscopic calculations.

The following data can be calculated using TALYS code:

 Total, elastic and reaction cross sections,

 Non-elastic cross sections per discrete state,

 Elastic and non-elastic angular distributions,

 Exclusive reaction channels ((n,2n), (n,np), etc.),

 Exclusive double-differential spectra,

 Exclusive isomeric production cross sections,

Chapter Three Theoretical Calculations  Discrete and continuum gamma-ray production cross sections,

 Total particle production cross sections e.g. (n,xn),

 Single- and double-differential particle spectra,

 Residual production cross sections (+ isomers),

 Recoils,

 Fission cross sections and fission yields.

Fig. 3.1 Flowchart of TALYS code.

Besides the ENDF-formatted data file, for each reaction channel all data are also produced in readable numerical form for plotting and graphical purposes. In our calculation by TALYS1.2 we used the default

Chapter Three Theoretical Calculations interface parameters to get the cross sections of the different reactions. TALYS website presents a nuclear data library TENDL-2010 which provides the output of the TALYS nuclear model code system. The third version is TENDL-2010, which is based on both default and adjusted TALYS calculations and data from other sources.

3.3. EMPIRE-03 (ARCOLA)

EMPIRE is a modular system of nuclear reaction codes, comprising various nuclear models, and designed for calculations over a broad range of energies and incident particles. The code involves the most important nuclear reaction mechanisms such as direct, preequilibrium and compound nucleus processes. We used the latest version of the code (EMPIRE-3.0, Arcola) in the present calculations. The following are the important features of this version:

 A broad range of energies (up to 150 MeV) and projectiles (any nucleon or HI).

 Most important nuclear reaction mechanisms.

 Ability to choice of models and parameterizations.

 Use extensive input parameter library (RIPL-2/3).

 Automatic retrieval of experimental data from EXFOR.

 Highly automated fit of optical model parameters.

 Automatic adjustment of remaining model parameters.

 Easy input (extensive use of defaults, built-in internal logic).

 Easy operation via Graphic User Interface (GUI).

 Interactive plots of experimental and calculated results:

 Excitation functions,  Angular distributions,

Chapter Three Theoretical Calculations  Inclusive emission spectra for n, p, α, and γ,  Double differential spectra.

 Resonance module - link to the Atlas of Neutron Resonances.

 ENDF-6 formatting.

 Utility codes (ENDF-6 verification).

 NJOY support.

A comprehensive library of input parameters covers nuclear masses, optical model parameters, ground state deformations, discrete levels and decay schemes, level densities, fission barriers, moments of inertia and gamma-ray functions.

The nuclear codes that used for various reaction mechanisms are:

 Spherical optical model (ECIS-06),

 Coupled Channels (ECIS-06),

 TUL approach to Multistep Direct (MSD) (ORION + TRISTAN),

 NVWY Multistep Compound (MSC) with γ-emission,

 Second-chance preequilibrium emission,

 Exciton model (PCROSS, DEGAS),

 Monte Carlo preequilibrium (DDHMS),

 HRTW for widths’ fluctuations,

 Hauser-Feshbach model with full γ-cascade and dynamical deformation effects,

 State of the art fission (multi-hump barriers, microscopic barriers, optical model for fission, multimodal fission).

Chapter Three Theoretical Calculations

The entire EMPIRE system can be divided into six major components:

1. Physics core,

2. Input parameter library,

3. Scripts and Graphic User Interfaces (GUI),

4. Utility codes,

5. Library of neutron resonances,

6. Library of experimental data (EXFOR).

The flowchart shown in Fig. 3.2 illustrates the organization of the system and indicates the flow of the data. The physics core, supported by the input parameter library, is the heart of the system. It consists of a number of modules written in FORTRAN that implement various nuclear reaction models and a number of stand-alone utility codes [Herman et al., 2007].

The direct interaction cross sections are calculated within the coupled-channel (CC) formalism, while the particle transmission coefficients for the emerging channels were calculated considering a spherical optical model. Additionally, the direct neutron scattering on non-coupled levels was considered by a Distorted Wave Born Approximation (DWBA) with dynamic deformations selected to describe available neutron emission spectra. All the optical model calculations were performed with the ECIS06 code [Raynal, 2005] incorporated into the EMPIRE system [Milocco et al., 2011].

The preequilibrium emission can be treated by

 The deformation dependent theories Multi-Step Direct (MSD) and Multi-Step Compound (MSC). The (Tamura, Udagawa and Lenske) TUL approach to MSD [Tamura et al., 1982] carried out by the codes ORION+TRISTAN, while the modeling of Multi-Step Compound (MSC) processes follows the approach of Nishioka et al. (NVWY) [Nishioka et al., 1986].

Chapter Three Theoretical Calculations

Fig. 3.2 Flowchart of EMPIRE code.

 Preequilibrium exciton models:

. DEGAS with full angular momentum coupling. The module DEGAS is the exciton model code with angular-momentum conservation written by E. Betak as an improved version of the code PEGAS by [Bĕták and Oblŏzinský, 1993].

. PCROSS with cluster emission. Preequilibrium emission was based on the one-component Griffin exciton model [Griffin, 1966]. There is no spin included in the PCROSS formulation, which is the main difference from the DEGAS treatment. The parameterization of internal transition rate proposed by [Blann and Mignerey, 1972] is used. Kalbach’s method [Cline and Blann, 1971; Cline, 1972; Kalbach, 1977] was implemented for the calculation of the nucleon emission rate. The preequilibrium

Chapter Three Theoretical Calculations mechanism for clusters in the incoming and outgoing channels treated by the Iwamoto-Harada model [Iwamoto and Harada, 1982] parameterized and improved in [Sato et al., 1983; Shang and Jun, 1989]. The probability of gamma emission (without spin selection rules) is derived in a way similar to the nucleon emission probability by applying the principle of detailed balance [Pluyko and Prokopets, 1978; Bĕták and Dobes, 1979; Akkermans and Gruppelaar, 1985].

 Monte-Carlo preequilibrium. The Hybrid Monte-Carlo Simulation (HMS) approach to the preequilibrium emission of nucleons has been formulated by [Blann, 1996] as a hybrid-model inspired version of the intranuclear cascade approach. There are no physical limits on the number of preequilibrium emissions (apart from energy conservation) in HMS. With the addition of linear momentum conservation by [Blann and Chadwick, 1985] (DDHMS), the model provides a nearly complete set of observables.

The statistical model used in the EMPIRE is an advanced implementation of the Hauser-Feshbach theory. The full γ-cascade in the residual nuclei is considered. The γ-emission involves E1, E2 and M1 transitions. To account for the correlation between incidence and exit channels inelastic scattering (width fluctuations) EMPIRE code uses the model proposed by Hofmann, Richert, Tepel and Weidenmueller (HTRW) [Hofmann et al., 1975]. The exact angular momentum and parity coupling is observed using l-dependent transmission coefficients. The emission of neutrons, protons, α- particles, deuterons, tritium and 3He is taken into account. Angular distributions of particles emitted from the compound nucleus are assumed to be isotropic. The E1, E2, and M1 transitions are taken into account in the statistical model (Hauser- Feshbach) default calculations using the giant multipole resonance model known as Brink-Axel hypothesis [Axel, 1962; Brink, 1957]. Six different shapes of the γ-ray strength function can be selected in the EMPIRE code:

 EGLO: Enhanced Generalized Lorentzian [Kopecky et al., 1993].

 MLO1, MLO2, MLO3: Modified Lorentzian [Plujko, 2000].

Chapter Three Theoretical Calculations  GFL: Generalized Fermi Liquid Model [Mughabghab and Dunford, 2000].

 SLO: Standard Lorentzian.

Several options of nuclear level densities include the EMPIRE- specific approach, which includes the dynamic deformation of fast rotating nucleus, the classical Gilbert–Cameron approach [Gilbert and Cameron, 1965] and pre-calculated tables obtained with a microscopic model based on Hartree-Fock-BCS (HFB) [Naoki Tajima, 2001] single- particle level schemes with collective enhancement.

In the present work 3He induced nuclear reactions on each stable isotope of natural cadmium have been reproduced using EMPIRE-3. The total cross section of a given isotope was obtained by weighting and summing the individual results of the reactions producing this isotope according to the abundance of the target isotopes.

Chapter Four Results and Discussion

CHAPTER IV RESULTS AND DISCUSSION

Chapter Four Results and Discussion As mentioned earlier, the experimental and theoretical excitation functions for 3He induced nuclear reactions on high purity natural cadmium (99.5 %) were calculated. Natural cadmium has eight sTable isotopes (106Cd 1.25 %, 108Cd 0.89 %, 110Cd 12.49 %, 111Cd 12.8 %, 112Cd 24.13 %, 113Cd 12.22 %, 114Cd 28.73 %, 116Cd 7.49 %) and hence, the formation cross section of any nuclide include contributions from reactions with different target isotopes. Direct and cumulative cross sections were calculated depending on the contributing processes and the activity measurements. The excitation functions of the reactions leading to the production of the radioisotopes 110,111,113,117mSn, 108,109,110m,g,111,113m,114m,115m,116m,117m,gIn, 111m,115Cd were evaluated from their respective threshold energies up to 27 MeV. The large number of radioisotopes and isomeric states obtained in the bombardment of cadmium also is a good occasion to test the prediction capabilities of different codes based on theoretical models.

In general, cadmium is an important material for nuclear technology; it is used in bearing alloys, in electroplating and in low melting point alloys. The activation of cadmium can therefore be used for estimation of depth distribution and dose [Tárkányi et al., 2006]. 117In, 117Cd, 111mCd, 111Cd, and 111In have been used for characterization of defects in semiconductors [Thomas Wichert and Manfred Deicher, 2001]. The radioactive props 111In/111Cd, 111mCd/111Cd and 117Cd/117In were used as an ideal tool for the determination of chemical nature, lattice location, thermodynamical properties, and dynamic behavior of intrinsic and extrinsic defects especially for semiconductor materials. 114mIn and 111In are used for therapy, in dual radioassy (dual-nuclide studies) with 51Cr, and used as radiolabel in many cellular research applications [Liburd et al., 1980]. 115mIn for labeling blood elements for evaluating inflammatory bowel disease and in dual-emitter studies [Ehrhardt et al., 1983]. The most important Single Photon Emission Computed Tomography (SPECT) isotope 111In is used for detection of heart transplant, imaging of abdominal infections, antibody labeling, cellular immunology, used with 67Ga for soft tissue infection detection and ostemyelitis detection, white blood cell imaging, cellular dosimetry, myocardial scans, treatment of leukemia, imaging tumors, and hemopoietic marrow scanning [Rayudu et al., 1973; Siciliano, 2004]. 109In, 110In are used for diagnostic purposes using the Positron Emission Tomography (PET) technique e.g. labeling and quantification of the uptake via PET measurements [Mark Lubberink et al., 2002]. 113mIn is

Chapter Four Results and Discussion used for Human Serum Albumin (HSA) microspheres labeling and clinical ventilation imaging. 117mSn is used for bone cancer pain relief and treatment of metastatic bone pain [Siciliano, 2004].

The stack consists of 11 natCd foils as a target placed together with 9 natTi foils for monitoring the 3He beam current and energy. The 3He beam current was observed from the current integrator and calculated from the monitor reaction. The incident energy was estimated also from the cyclotron parameters and monitor reaction. A good agreement was obtained between the evaluation of the current and energy utilizing the experimental parameters and the evaluation using the excitation function of the adapted monitor reaction by the IAEA i.e. natTi(3He,x)48V. The experimental excitation function of this reaction compared with the adapted excitation function from IAEA was presented in Fig. 4.1. The measured cross section results and their errors for this reaction were presented in Table 4.1. The measurements of the activity of 48V have been performed 10 days after the EOB. That is because there is an overlapping between the gamma line Eγ= 1312.10 keV, Iγ= 97.5 % comes 48 from the decay of V (T1/2= 15.97 day), and the line Eγ= 1312.10 keV, 48 Iγ= 100.1 % comes from the decay of Sc (T1/2= 43.67 hours). So we performed the activity measurements after the total decay of 48Sc to avoid this overlapping. The incident energy was estimated at 26.4±0.3 MeV. The 3He beam current was evaluated at about 100 nA during the irradiation. Uncertainty on the median energy in each foil is increasing along the stack due to the cumulative effect of energy spread and variations in foils thickness and reaches a maximum of ±1.3 MeV on the last foil.

The uncertainties were estimated in the standard way [ISO, 1995]; the linearly contributing independent processes were taken into account extracting square root of quadratically summed relative uncertainties. The following individual uncertainties are taken into account: number of bombarding particles (7 %), determination of the thickness of each foil (3 %), decay data (3 %), detector efficiency (7 %), and peak area (10 %). The total uncertainties of the cross section values were evaluated to be approximately 15 %, in some cases even higher. The decay characteristics of all the investigated radioisotopes were taken from [Ekstrom and Firestone, 2000] and were given with their producing reactions in Table 4.2.

Chapter Four Results and Discussion Table. 4.1 Measured cross sections and their errors for natTi(3He,x)48V.

Energy (MeV) Cross section (mb) 25.60±0.33 311±36.00 22.63±0.47 192.47±22.71 20.89±0.55 129.43±15.13 19.10±0.63 83.15±10.53 17.10±0.72 63.16±8.29 14.94±0.82 53.59±6.81 12.57±0.92 55.35±6.64 9.87±1.10 19.98±2.38 6.59±1.20 3.98±0.76

400 This work 350 IAEA recommended data 300 250 200 150 natTi(3He,x)48V

100 Cross section (mb) section Cross 50 0 0 3 6 9 12 15 18 21 24 27 30 3 He -particle energy (MeV)

Fig. 4.1 Excitation function of the monitor reaction natTi(3He,x)48V.

Chapter Four Results and Discussion Table. 4.2 Decay data and contributing reactions of the investigated products.

Decay Contributing Q Value E Half- E (I ) Product th Mode γ γ (MeV) (MeV) life reaction (%) (keV) (%) 108Cd(3He,n) 3.45 0 110Sn EC 110Cd(3He,3n) - 13.79 14.17 4.11 h 283 (97) (100) 111Cd(3He,4n) - 20.76 21.32 110Cd(3He,2n) - 5.62 5.77 EC+β+ 111Sn 111Cd(3He,3n) - 12.59 12.93 35.3 m 1152.98 (2.7) (100) 112Cd(3He,4n) - 21.98 22.57 111Cd(3He,n) 5.93 0 391.69 (64) 112Cd(3He,2n) - 3.46 3.55 EC+β+ 113gSn 115.1 d 113Cd(3He,3n) - 10.0 10.26 (100) 255.05 (1.82) 114Cd(3He,4n) - 19.04 19.54 117mSn 116Cd(3He,2n) 0.47 0 IT (100) 13.6 d 158.56 (86) 204.97 (47) 106Cd(3He,np) - 4.0 4.11 EC+β+ 107gIn 32.4 m 320.92 (10.2) 108Cd(3He,3np) - 1.78 1.83 (100) 505.51 (11.9) 106 3 + 108g Cd( He,p) 4.62 0 EC+β 875.47 (100) In 108 3 58 m Cd( He,2np) - 13.63 14.01 (100) 242.75 (41) 108Cd(3He,np) - 3.19 3.28 EC+β+ 203.5 (74) 109gIn 4.2 h 110Cd(3He,3np) - 20.43 20.99 (100) 426.25 (4.12) 884.69 (92.9) 108Cd(3He,p) 4.86 0 EC+β+ 937.49 (68.4) 110gIn 110Cd(3He,2np) - 12.37 12.71 4.9 h (100) 707.4 (29.5) 111Cd(3He,3np) - 19.35 19.87 641.68 (25.9) 108Cd(3He,p) 4.86 0 EC+β+ 657.76 (98) 110mIn 110Cd(3He,2np) - 12.37 12.71 69.1 m (100) 111Cd(3He,3np) - 19.35 19.87 1125.7 (1.02) 110Cd(3He,np) - 2.39 2.45 111Cd(3He,2np) - 9.36 9.61 111gIn EC (100) 2.81 d 171.28 (90) 112Cd(3He,3np) - 18.75 19.25 113Cd(3He,4np) - 25.29 25.96 111Cd(3He,p) 7.75 0 112Cd(3He,np) - 1.64 1.68 113mIn IT (100) 1.66 h 391.69 (64.2) 113Cd(3He,2np) - 8.18 8.40 114Cd(3He,3np) - 17.22 17.67 112Cd(3He,p) 5.63 0 IT 114mIn 49.51 d 190.3 (15.56) 113Cd(3He,np) - 0.91 0.93 (96.75)

Chapter Four Results and Discussion

114Cd(3He,2np) - 9.95 10.21 EC+β+ 116Cd(3He,4np) - 24.78 25.43 (3.25) 113Cd(3He,p) 8.13 0 115m 114 3 IT (95) 336.24 In Cd( He,np) - 0.91 0.94 - 4.49 h β (5) (45.83) 116Cd(3He,3np) - 15.75 16.16 1293.56 114Cd(3He,p) 5.87 0 (84.4) 116mIn β- (100) 54.29 m 116Cd(3He,2np) - 8.97 9.20 1097.33 (56.2) 117gIn 116Cd(3He,np) - 0.20 0.21 β- (100) 43.2 m 553 (100) β- (52.9) 117mIn 116Cd(3He,np) - 0.20 0.21 116.2 m 315.30 (19) IT (47.1) 110Cd(3He,2p) - 0.74 0.76 111Cd(3He,n2p) - 7.72 7.92 112Cd(3He,α) 11.18 0 111mCd IT (100) 48.54 m 150.82 (29.1) 113Cd(3He,nα) 4.64 0 114Cd(3He,2nα) - 4.40 4.51 116Cd(3He,4nα) - 19.23 19.73 114Cd(3He,2p) - 1.58 1.62 527.9 (27.45) 115gCd β- (100) 53.46 h 116Cd(3He,α) 11.87 0 492.3 (8.03)

The cross section data reported here are not of high enough resolution to depict the individual contribution of the various processes involved. For most of reactions, these data represent the first consistent sets of data.

Below we have introduced the investigated reactions in three categories; formation of tin isotopes, formation of indium isotopes and formation of cadmium isotopes. The first category i.e. formation of tin isotopes is mainly performed via the reactions (3He,xn) since the other reaction mode (3He,γ) is often neglected. In the second category the indium isotopes are formed mainly via the reactions (3He,p) and (3He,pxn). In the third category, cadmium isotopes are formed via the reactions (3He,2p) and (3He,2pxn). In addition, indium and cadmium isotopes may be also produced via cluster emission i.e. deuterons, tritons and alpha particles.

Chapter Four Results and Discussion 4.1. EXCITATION FUNCTIONS OF TIN ISOTOPES

4.1.1. FORMATION OF 117mSn

117 The isomeric state of Sn with half life T1/2= 13.6 d, spin and parity Jπ = 11/2- decays by 100 % Isomeric Transition (IT). Hence, this radioisotope is practically pure gamma emitter. It decays to its ground state through either one direct transition, with Eγ= 314 keV, Iγ= 0.0004 % or two transitions on cascade, the first is relatively low intensity line with Eγ= 156.02 keV, Iγ= 2.113 % and the second leads to a 158.562 keV γ- ray (Iγ= 86 %) which is the radiation of interest for medical applications, especially for SPECT techniques. The 158.562 keV line is overlapped with another line emitted through the decay of 117mIn and/or 117gIn. The half lives of them are however, short in comparison to the half life of 117mSn (see Table 4.2) hence, late measurements of the 158.562 keV gamma line are only very slightly influenced by the initial presence of 117m,gIn. We used the fourth measurement of the 158.562 keV line in the cross section calculations. Since 117gIn decays to 117Sn by 100 % β-, the formation cross section of 117mSn is a cumulative process.

117mSn is formed via the reaction channels 114Cd(3He,γ) and 116Cd(3He,2n). The measured formation cross section values and their errors for the 117mSn formation are presented in Table 4.3.

The excitation function shows a peak of about 2.75 mb maximum at 18 MeV, Fig. 4.2.

[Montgomery and Porile, 1969] irradiated 97.2 % enriched 116Cd with 3He ions in the energy range 33-13 MeV. We normalized their data by extrapolation to natural abundance. The present data is in more or less in agreement with [Montgomery and Porile, 1969] especially in the trend of the excitation function curve. A difference of about 25 % decrease in the maximum reported value and an energy shift of about 1.4 MeV can be seen.

[Qaim and Döhler, 1984] irradiated natural cadmium with 3He ions up to 120 MeV. Two points of their data are in our energy range;

Chapter Four Results and Discussion their values represent about 60 % from the present data. Their maximum cross section value is 1.6 at about 18 MeV.

The theoretical code ALICE-IPPE represents the sum of cross sections of the ground and isomeric states. It has somehow the same trend with higher cross section values than the present data. However, we applied the isomeric ratios calculated with TALYS to the total cross sections calculated with ALICE-IPPE to generate separate values for the ground and isomeric states. In this way ALICE results for 117mSn have more or less the same behavior of the present data with higher values; about 150 % in the higher energy range over 20 MeV. TALYS and TENDL have also the same behavior but with lower values than the present work. They extremely match each other. EMPIRE code has different trend and higher values. All the codes however agreed that the channel (3He,γ) can be neglected; it has no significant effect on the reaction. Hence the dominant channel is (3He,2n).

Table. 4.3 Measured cross sections and their errors for 116Cd(3He,2n)117mSn.

Energy (MeV) Cross section (mb) 26.36±0.30 1.24±0.28 24.81±0.37 1.54±0.31 23.45±0.43 1.87±0.32 21.76±0.51 2.15±0.37 19.97±0.59 2.14±0.35 18.10±0.68 2.75±0.41 16.00±0.77 1.10±0.28

Chapter Four Results and Discussion

5 This work 116 3 117m cum Montgomery & Porile Cd( He,2n) Sn Qaim & Dohler 4 ALICE 117g+mSn ALICE 117mSn 3 EMPIRE TALYS TENDL 2

1 Cross section (mb) section Cross

0 0 5 10 15 20 25 30 35 3He -particle energy (MeV)

Fig. 4.2 Excitation function of 116Cd(3He,2n)117m cumSn reaction.

113g 4.1.2. FORMATION OF Sn

113 π + The long-lived nuclide Sn with T1/2= 115.09 d and J = 1/2 + 113m 113 decays by 100 % EC+β to In (T1/2= 99.5 m). Sn has only one strong gamma line with Eγ= 391.69 keV, Iγ= 64 %. This line is overlapped with another one emitted from the decay of 113mIn. But, due to short half life of 113mIn compared to 113gSn, a convenient long cooling time is enough for total decay of that indium isotope. However, after the total decay of 113mIn, it is produced continuously again through the decay of the 113gSn isotope and hence, always some contamination will affect the cross section data. The formation of 113Sn is a cumulative process 113m π + since the isomeric state Sn with (T1/2= 21.4 m, J = 7/2 ) decays to its ground state by 91.1 % IT and we start measurements after the total decay of this isomeric state.

113Sn is formed via a combination of four reaction channels 111Cd(3He,n), 112Cd(3He,2n), 113Cd(3He,3n) and 114Cd(3He,4n). The measured cross section values and their errors for the 113Sn formation are presented in Table 4.4.

The cross section increases slightly with the energy up to about 20 MeV then a plateau region appear and then again increases up to a maximum of about 158 mb at the end of energy range, see Fig. 4.3. The

Chapter Four Results and Discussion regrowth of the cross section after the plateau may indicate the opening 114 3 of the Cd( He,4n) channel with threshold energy Eth= 19.5 MeV. The experimental threshold at about 13 MeV may indicate the opening of the 113 3 Cd( He,3n) channel (Eth= 10.26 MeV).

Two points of [Qaim and Döhler, 1984] data are in our energy range, and they are in a good agreement with the present data.

Table. 4.4 Measured cross sections and their errors for natCd(3He,xn)113Sn.

Energy (MeV) Cross section (mb) 26.36±0.30 158.25±18.70 24.81±0.37 149.37±17.22 23.45±0.43 131.73±15.70 21.76±0.51 127.82±15.28 19.97±0.59 120.23±14.41 18.10±0.68 92.96±11.35 16.00±0.77 21.20±3.37 13.76±0.87 2.49±1.30

ALICE code data for the total (ground and isomeric) cross section has the same trend of the present data. The code data match more or less the present data in the high energy range over 20 MeV but has higher values in lower energy range. This is because ALICE code give high 112 3 results for the channel Cd( He,2n) (Eth= 3.55 MeV) that opened around 5 MeV. However, ALICE results for the ground state only have different trend and magnitude. Analysis of the code by resolving it to its elemental cross section values showed that the regrowth of the cross section indicates the opening of the 114Cd(3He,4n) channel. EMPIRE code results are far from the present results and even they haven’t the same behavior. TALYS and TENDL have different trend from the present data and have too lower values.

Chapter Four Results and Discussion 200 This work 180 Qaim & Dohler 160 ALICE 113g+mSn 140 ALICE 113gSn EMPIRE 120 TALYS*10 100 TENDL*10 80 60 Cross section section Cross (mb) 40 natCd(3He,xn)113 cumSn 20 0 8 11 14 17 20 23 26 3 He -particle energy (MeV)

Fig. 4.3 Excitation function of the natCd(3He,xn)113Sn reaction.

111 4.1.3. FORMATION OF Sn

111 π + + Sn with T1/2= 35.3 m and J = 7/2 decays by 100 % EC+β directly or through excited states to 111In. There are a lot of gamma lines in the decay scheme of 111Sn, all with low intensities. We used the highest intensity line with Eγ= 1152.98 keV and Iγ= 2.7 % in the cross section calculation.

111Sn is formed via a combination of the reactions 110Cd(3He,2n), 111Cd(3He,3n) and 112Cd(3He,4n). The measured cross section values and their errors for the 111Sn formation are presented in Table 4.5.

The cross section increases with the energy until it reaches a maximum value of about 73.5 mb at 26.4 MeV with high error values mainly due to the low intensity of the gamma line that used in the cross section calculation Fig. 4.4. The excitation function curve has low resolution to be resolved to describe the opening of different contributing channels.

Chapter Four Results and Discussion [Szelecsényi et al., 1991] irradiated natural cadmium with 3He up to 27 MeV. Their data match well the present data.

ALICE and EMPIRE have the same trend and magnitude; they match well each other especially below 20 MeV. They have the same trend of the present data but their cross section values represent twice as the present values. Note that, there are no isomeric states for this isotope. Hence the ALICE code results which represent the total cross sections, equal to the ground state cross sections. TALYS and TENDL match each other very well in trend and magnitude but they don’t describe the present data; they have lower values.

Table. 4.5 Measured cross sections and their errors for natCd(3He,xn)111Sn.

Energy (MeV) Cross section (mb) 26.36±0.30 73.49±18.30 24.81±0.37 69.60±12.27 23.45±0.43 68.01±10.70 21.76±0.51 50011±12.37 19.97±0.59 48.65±10.84 18.01±0.68 33.11±6.31

140 This work Szelecsenyi et al. 120 ALICE 100 EMPIRE TALYS 80 TENDL 60 40 nat 3 111

Cross section (mb) section Cross Cd( He,xn) Sn 20 0 10 13 16 19 22 25 28 3He -particle energy (MeV)

Fig. 4.4 Excitation function of the natCd(3He,xn)111Sn reaction.

Chapter Four Results and Discussion 110 4.1.4. FORMATION OF Sn

110 π + Sn with T1/2= 4.11 h, J = 0 decays by 100 % EC directly to 110m In through a single gamma line with Eγ= 283 keV, Iγ= 97 % - a contradictory between our source of decay data and the NUDAT2 website Database [http://www.nndc.bnl.gov/nudat2/] that supplied by the Natural Nuclear Data Center (NNDC) Brookhaven in the energy and intensity of this line; Lund database gives only relative intensity for a line at 280.46 keV, thus, we used the NUDAT2 clear values in the cross section calculations-.

110Sn is formed via a combination of three reaction channels 108Cd(3He,n), 110Cd(3He,3n) and 111Cd(3He,4n). The cross section values and their errors for the formation of 110Sn are presented in Table 4.6.

The excitation function increases continuously with the energy to a maximum of about 73.1 mb at 26.4 MeV Fig. 4.5. The excitation function curve has low resolution to be resolved to describe the opening of different contributing channels.

The present results are in good agreement with [Szelecsényi et al., 1991] in the low energy range but, the present results slightly exceed them with increasing the energy.

Table. 4.6 Measured cross sections and their errors for natCd(3He,xn)110Sn.

Energy (MeV) Cross section (mb) 26.36±0.30 73.13±8.23 24.81±0.37 66.48±7.48 23.45±0.43 52.19±5.88 21.76±0.51 32.01±3.61 19.97±0.59 14.24±1.62 18.01±0.68 3.11±0.38

The ALICE code results are higher than the present results but more or less have the same trend. TALYS and TENDL match each other especially in the trend but they don’t describe the present data; they have

Chapter Four Results and Discussion lower values. EMPIRE code has same trend of the present data with lower cross section values. The code describes well [Szelecsényi et al., 1991] data in trend and magnitude.

100 This work Szelecsenyi et al. 80 ALICE EMPIRE 60 TALYS TENDL

nat 3 110

20 Cd( He,xn) Sn Cross section (mb) section Cross

0 15 17 19 21 23 25 27 3He -particle energy (MeV)

Fig. 4.5 Excitation function of the natCd(3He,xn)110Sn reaction.

4.2. EXCITATION FUNCTIONS OF INDIUM ISOTOPES

117m,g 4.2.1 FORMATION OF In

117g π + - In isotope with T1/2= 43.2 m and J = 9/2 , decays by 100 % β to 117 Sn. A set of gamma lines with only two strong intensity lines at Eγ= 158.56 keV, Iγ= 87 % and Eγ= 553 keV, Iγ= 100 % are emitted through 117gIn decay.

117m π - The isomeric state In with T1/2= 116.2 m and J = 1/2 , branched decay by: 52.9 % by β- to 117Sn and 47.1 % by IT. Again a set of gamma lines with only two strong intensity lines with Eγ= 158.56 keV, Iγ= 16 % and Eγ= 315 keV, Iγ= 19 % (that corresponds to the isomeric transition) emitted through the decay of 117mIn. We excluded the line 158.56 keV from the cross section calculations since it comes also through the decay of the isomeric state 117mSn which has longer half live than both of

Chapter Four Results and Discussion 117m,gIn. Therefore, we used the other two lines in the cross section calculations. Due to the 47.1 % IT from the 117mIn, the excitation function of the 117gIn isotope is a cumulative process.

117m,gIn are formed via a single channel; 116Cd(3He,np). The formation via cluster emission i.e. by deuteron emission may be also allowable. There is no previous available experimental data for this reaction. The cross section values and their errors for the formation of 117m,gIn are presented in Table 4.7.

The excitation function for the ground state isotope increases with the energy up to 20 MeV and then shows a plateau region up to the end of the energy range Fig. 4.6.

Table. 4.7 Measured cross sections and their errors for natCd(3He,x)117m,gIn.

Cross section (mb) Energy (MeV) 117gIn 117mIn 26.36±0.30 14.19±1.64 4.36±0.90 24.81±0.37 15.63±1.78 4.67±0.83 23.45±0.43 16.01±1.83 4.75±0.88 21.76±0.51 15.58±1.77 4.88±0.82 19.97±0.59 14.98±1.70 4.68±0.73 18.01±0.68 11.83±1.35 4.54±0.68 16.01±0.77 3.12±0.37 1.66±0.40 13.76±0.87 0.30±0.05

The theoretical data in ALICE (for total cross section and for ground state cross section), TALYS and TENDL do not match anyway the experimental data; they have lower values. EMPIRE code results describe the present data more or less in the low energy range at about 20 MeV and then go higher.

The isomeric state 117mIn excitation function has the same behavior of that of its ground state 117gIn. The excitation function increases with the energy up to 18 MeV and then shows a plateau region up to the end of the energy range Fig. 4.7.

Chapter Four Results and Discussion

20 This work 18 ALICE 117g+mIn 16 ALICE 117gIn 14 EMPIRE TALYS 12 TENDL 10 116 3 117g 8 Cd( He,np) In 6

Cross section (mb) section Cross 4 2 0 10 12 14 16 18 20 22 24 26 28 3He -particle energy (MeV)

Fig. 4.6 Excitation function of the natCd(3He,x)117gIn reaction.

ALICE results for the total formation cross section and the isomeric cross section have lower values than the present results and even have different behavior. The EMPIRE code describes the experimental excitation function in behavior in the energy range over 18 MeV but the code results represent about 50 % from the experimental results in this energy range. Both TALYS and TENDL have lower results than the experimental results. TALYS represents about 30 % of TENDL values with more or less the same trend; an energy shift of about 2 MeV can be seen.

6 This work ALICE 117g+mIn 5 ALICE 117mIn EMPIRE 4 TALYS

TENDL 116 3 117m 3 Cd( He,np) In

2 Cross section section (mb) Cross 1

0 10 12 14 16 18 20 22 24 26 28 3He -particle energy (MeV)

Chapter Four Results and Discussion Fig. 4.7 Excitation function of the natCd(3He,x)117mIn reaction.

116m 4.2.2 FORMATION OF In

116 π + In has two isomeric states with T1/2= 54.29 m, J = 5 and T1/2= 2.18 s, Jπ= 8-. The short lived isomeric state decays by 100 % IT to the long lived one; thus, we calculated the cumulative production cross section for the first isomeric state.

116m1In decays by 100 % β- to 116Sn through a lot of gamma lines. Two lines with Eγ= 1097.33 keV, Iγ= 56.2 % and Eγ= 1293.56 keV, Iγ= 84.4 % were used in the cross section calculation.

Two channels can contribute in the formation of 116mIn; 114Cd(3He,p) and 116Cd(3He,2np). There is no previous available experimental data for this reaction. The cross section values and their errors for the formation of 116mIn are presented in Table 4.8.

The excitation function increases continuously with the energy up to a maximum of about 22 mb at 26.4 MeV Fig. 4.8. The shape of the excitation function does not indicate the opening of any channel.

Table. 4.8 Measured cross sections and their errors for natCd(3He,x)116mIn.

Energy (MeV) Cross section (mb) 26.36±0.30 21.94±2.56 24.81±0.37 20.46±2.36 23.45±0.43 16.38±1.91 21.76±0.51 11.54±1.37 19.97±0.59 7.51±0.88 18.01±0.68 3.71±0.52 16.01±0.77 0.55±0.10

Chapter Four Results and Discussion

25 This work natCd(3He,x)116m1 cumIn ALICE 116g+mIn 20 ALICE 116mIn EMPIRE TALYS 15 TENDL

10 Cross section section Cross (mb) 5

0 10 12 14 16 18 20 22 24 26 28 30 3He -particle energy (MeV)

Fig. 4.8 Excitation function of the natCd(3He,x)116mIn reaction.

ALICE code for the total cross section has the same trend of the excitation function. The code results represent about 30 % of the experimental results. On the other hand ALICE code for only the isomeric cross section has also the same trend of the excitation function. The code results represent about 15 % of the experimental. EMPIRE, TALYS and TENDL have different behavior and magnitudes from the present data.

115m 4.2.3 FORMATION OF In

The ground state of 115In has a half life of 4.41E14 y, so its presence could not be measured in our experimental circumstances. 115m π - In with T1/2= 4.49 h, J = 1/2 branched decay; 95 % IT through a - single gamma line of (Eγ= 336.24 keV, Iγ= 45.83 %) and 5 % β to the 115 ground state of Sn through a single gamma line of (Eγ= 497.36 keV, 115m Iγ= 0.047 %). We identified the In isotope by its strongest gamma 115g line i.e. the 336.24 keV line. As Cd with T1/2= 53.38 h decays to 115mIn, only the first measurement can be used for 115mIn cross section calculation when the in-growth is still very small. Using the first measurement also prevents an overlapping between the 115mIn strongest gamma line and another line with the same energy comes through the decay of the longer lived 115gCd isotope.

Chapter Four Results and Discussion Table. 4.9 Measured cross sections and their errors for natCd(3He,x)115mIn.

Energy (MeV) Cross section (mb) 26.36±0.30 25.78±3.23 24.81±0.37 31.36±3.68 23.45±0.43 32.85±3.85 21.76±0.51 34.29±3.91 19.97±0.59 36.68±4.17 18.01±0.68 31.16±3.55 16.01±0.77 10.95±1.29 13.76±0.87 1.13±0.18

Three opened channels can contribute for the 115mIn formation; 113Cd(3He,p), 114Cd(3He,np) and 116Cd(3He,3np). There is no previous available experimental data for this reaction. The cross section values and their errors for the formation of 115mIn are presented in Table 4.9.

The excitation function shows a broad peak with maximum of about 36.7 mb at 20 MeV Fig. 4.9.

All the theoretical codes have different behaviors and magnitudes from the experimental data.

45 This work natCd(3He,x)115mIn 40 ALICE 115g+mIn 35 ALICE 115mIn EMPIRE 30 TALYS 25 TENDL 20 15

Cross section section Cross (mb) 10 5 0 10 12 14 16 18 20 22 24 26 28 3He -particle energy (MeV)

Fig. 4.9 Excitation function of the natCd(3He,x)115mIn reaction.

Chapter Four Results and Discussion

114m 4.2.4 FORMATION OF In

114 π + In has two isomeric states with T1/2= 49.51 d, J = 5 and T1/2= 43.1 ms, Jπ= 8- respectively. As the short lived isomeric state decays to the long lived one by 100 % IT, the cross section of 114m1In is a cumulative process. 114m1In branched decay by; 96.75 % IT to its ground state through a single gamma line with Eγ= 190.29 keV, Iγ= 15.56 % and + 114 3.25 % EC+β to the sTable Cd through two gamma lines with Eγ= 558.46 keV, Iγ= 3.24 % and Eγ= 725.30 keV, Iγ= 3.24 %. We used the isomeric transition gamma line (190.29 keV) in our cross section calculations.

Table. 4.10 Measured cross sections and their errors for natCd(3He,x)114mIn.

Energy (MeV) Cross section (mb) 26.36±0.30 100.56±11.90 24.81±0.37 93.62±11.27 23.45±0.43 74.13±8.97 21.76±0.51 49.29±6.38 19.97±0.59 37.32±7.18 18.01±0.68 23.31±3.84 16.01±0.77 4.45±2.72

114mIn isotope is formed via a contribution of the processes 112Cd(3He,p), 113Cd(3He,np), 114Cd(3He,2np) and 116Cd(3He,4np). There is no previous available experimental data for this reaction. The cross section values and their errors for the formation of 114mIn are presented in Table 4.10.

The excitation function increases continuously to a maximum of about 100.6 mb at 26.4 MeV Fig. 4.10.

ALICE code data follows the shape of the experimental data. ALICE code results for the total cross section represent about 33 % of the experimental results. On the other hand, ALICE code results for the

Chapter Four Results and Discussion isomeric state only represent more or less about 28 % of the experimental results. EMPIRE code describes well the present data in trend and magnitude. TALYS and TENDL have higher results than the experimental work and have different behavior.

180 This work 160 ALICE 114g+mIn 140 ALICE 114mIn EMPIRE 120 TALYS 100 TENDL 80 nat 3 114m cum 60 Cd( He,x) In

Cross section section Cross (mb) 40 20 0 10 12 14 16 18 20 22 24 26 28 3He -particle energy (MeV)

Fig. 4.10 Excitation function of the natCd(3He,x)114mIn reaction.

113m 4.2.5 FORMATION OF In

113m π - The isomeric state In with T1/2= 1.66 h, J = 1/2 decays by 100 % IT through a single gamma line of Eγ= 391.69 keV, Iγ= 64.2 %. We used this gamma line to evaluate the cross section. As the long lived 113g + 113m nuclide Sn (T1/2= 115.09 d) decays by 100 % EC+β to In, only the first measurement could be used for 113mIn cross section calculation when the in-growth is still very small. The use of the first measurement also prevented interference between the gamma line that used in the cross section calculation and another line comes through the decay of 113gSn.

113mIn is formed via a contribution of the processes 111Cd(3He,p), 112Cd(3He,np), 113Cd(3He,2np) and 114Cd(3He,3np). There is no previous available experimental data for this reaction. The cross section values and their errors for the formation of 114mIn are presented in Table 4.11.

Chapter Four Results and Discussion The excitation function shows abroad peak with a maximum of about 38 mb at 23.5 MeV Fig. 4.11.

Table. 4.11 Measured cross sections and their errors for natCd(3He,x)113mIn.

Energy (MeV) Cross section (mb) 26.36±0.30 32.42±3.71 24.81±0.37 37.42±4.22 23.45±0.43 37.97±4.29 21.76±0.51 37.83±4.27 19.97±0.59 37.46±4.22 18.01±0.68 29.58±3.34 16.01±0.77 8.43±0.97 13.76±0.87 0.92±0.12 11.24±0011 0.05±0.02

50 This work ALICE 113g+mIn 40 ALICE 113mIn EMPIRE TALYS 30 TENDL

20 natCd(3He,x)113mIn

Cross section section Cross (mb) 10

0 10 12 14 16 18 20 22 24 26 28 3He -particle energy (MeV)

Fig. 4.11 Excitation function of the natCd(3He,x)113mIn reaction.

ALICE code for the total cross section and for the isomeric cross section data have different behavior from the experimental excitation function. The code results are lower than the present results. EMPIRE code has more or less the same behavior of the experimental data. The

Chapter Four Results and Discussion code results represent about 30 % of the present results. TALYS and TENDL have different trend and magnitudes from the experimental data.

111g 4.2.6 FORMATION OF In

111 π + In isotope has a ground state with T1/2= 2.8 d, J = 9/2 decays by 111 π 100 % EC to Cd and a short lived isomeric state with T1/2= 7.7 m, J = 1/2- decays by 100 % IT. The formation of 111gIn from natural cadmium is cumulative because of the IT of 111mIn and the 100 % EC+β+ decay of 111 111g Sn (T1/2= 35.3 m) to In. Hence measurements should start after a suitable cooling time to get the cumulative cross section (the third and fourth measurements were used for cross section calculation). Two strong gamma lines with Eγ= 171.28 keV, Iγ= 90 % and Eγ= 245.40 keV, 111g Iγ= 94 % were used to evaluate the In formation cross section.

111In is formed via a combination of the processes 110Cd(3He,np), 111Cd(3He,2np), 112Cd(3He,3np) and 113Cd(3He,4np). There is no previous available experimental data for this reaction. The cross section values and their errors for the formation of 114mIn are presented in Table 4.12.

The excitation function goes up with the energy to a maximum of about 237 mb at 25 MeV Fig. 4.12.

Table. 4.12 Measured cross sections and their errors for natCd(3He,x)111gIn.

Energy (MeV) Cross section (mb) 26.36±0.30 228.44±25.76 24.81±0.37 236.56±26.66 23.45±0.43 219.69±24.78 21.76±0.51 192.83±21.79 19.97±0.59 158.85±18.12 18.01±0.68 101.11±11.52 16.01±0.77 16.38±2.28 13.76±0.87 1.74±0.37

Chapter Four Results and Discussion All the theoretical codes have more or less the same behavior of the excitation function. ALICE code results for the total cross section and that for the ground state cross section represent about 14 % and 8 % of the present results respectively. EMPIRE code results are about 30 % of the present results. TALYS and TENDL results are identical and they represent about 55 % of the present results.

300 This work 250 ALICE 111g+mIn ALICE 111gIn 200 EMPIRE TALYS 150 TENDL

100

natCd(3He,x)111 cumIn Cross section section (mb) Cross 50

0 10 12 14 16 18 20 22 24 26 28 3He -particle energy (MeV)

Fig. 4.12 Excitation function of the natCd(3He,x)111gIn reaction.

110m,g 4.2.7 FORMATION OF In

110 π + The ground state of In with T1/2= 4.9 h, J = 7 decays by 100 % EC+β+ to the ground state of 110Cd. Many independent gamma lines are emitted through the decay of 110gIn. We used more than line to assist the 110g formation cross section of In namely (Eγ= 884.69 keV, Iγ= 92.9 %), (Eγ= 937.49 keV, Iγ= 68.4 %), (Eγ= 707.4 keV, Iγ= 29.5 %), and (Eγ= 641.68 keV, Iγ= 25.9 %).

110 π + The isomeric state of In with T1/2= 69.1 m, J = 2 decays also by 100 % EC+β+ to the ground state of 110Cd. The only suiTable gamma line for identification of the isomeric cross section is the strongest intensity line at Eγ= 657.76 keV, Iγ= 98 %. This line unfortunately, is overlapped 110g with a line from the decay scheme of In at Eγ= 657.76 keV, Iγ= 98.3 %. There is also another gamma line for the isomeric state but with low

Chapter Four Results and Discussion 110 intensity with Eγ= 1125.7 keV, Iγ= 1.02 %. As Sn with T1/2= 4.1 h decays by 100 % EC to 110mIn the formation of the isomeric state is cumulative.

For determination of the cumulative cross section of the isomeric state we need a correction of the contributions on the line 657.76 keV. By taking into account the activities of the independent lines of the ground state and the ratios of efficiencies and abundances we got the activity of the contaminated line (657.76 keV) for the ground state and the isomeric state separately. Then we used this activity to calculate the cross sections of the ground state and the isomeric state.

The cross section values calculated for the ground state using the derived activity agreed with that produced from the other independent gamma lines. In order to assure the isomeric state cross section values evaluated using the derived activity, we calculated the cross section of 110mIn using the low intensity gamma line (1125.7 keV). The cross section values obtained by the two methods are in agreement to each other.

Table. 4.13 Measured cross sections and their errors for natCd(3He,x)110m,gIn.

Cross section (mb) Energy (MeV) 110gIn 110mIn 26.36±0.30 23.72±2.71 67.91±7.63 24.81±0.37 16.83±1.93 57.02±6.41 23.45±0.43 10.11±1.23 40.39±4.54 21.76±0.51 3.81±0.58 22.21±2.50 19.97±0.59 0.85±0.29 9.64±1.08 18.01±0.68 0.01±0.01 2.10±0.24

Many channels contributes in the production of 110In in our energy range; 108Cd(3He,p), 110Cd(3He,2np) and 111Cd(3He,3np). There is no previous available experimental data for this reaction. The cross section values and their errors for the formation of 110m,gIn are presented in Table 4.13.

Chapter Four Results and Discussion For the ground state excitation function increases continuously with the energy up to a maximum of about 23.7 mb at 26.4 MeV Fig. 4.13.

30 This work natCd(3He,x)110gIn ALICE 110g+mIn 25 ALICE 110gIn EMPIRE 20 TALYS TENDL 15

10 Cross section section (mb) Cross 5

0 16 17 18 19 20 21 22 23 24 25 26 27 28 3He -particle energy (MeV)

Fig. 4.13 Excitation function of the natCd(3He,x)110gIn reaction.

80 This work 70 ALICE 110g+mIn ALICE 110mIn 60 EMPIRE 50 TALYS TENDL 40

30 natCd(3He,x)110mIn

Cross section section Cross (mb) 20 10 0 16 17 18 19 20 21 22 23 24 25 26 27 28 3He -particle energy (MeV)

Fig. 4.14 Excitation function of the natCd(3He,x)110mIn reaction.

ALICE code data (for the total cross section of isomeric and ground states) follows closer the experimental points. ALICE code data for only the ground state has lower values and different shape from the present work. EMPIRE code results also are in a good agreement to the

Chapter Four Results and Discussion present results. TALYS and TENDL results are in good agreement to each other. Their results are higher than the experimental results with more or less the same trend.

On the other hand the excitation function of the isomeric state increases continuously with the energy up to a maximum of about 68 mb at 26.4 MeV Fig. 4.14 which is the same behavior of the ground state excitation function.

The ALICE results for the total formation represent about 30 % of the experimental results while, ALICE results for only the isomeric state formation represent about 15 %. EMPIRE results represent about 14 % of the experimental results. TALYS and TENDL again are in agreement to each other. Also their results are higher than the experimental results with somehow the same trend.

109g 4.2.8 FORMATION OF In

109 π + The ground state of In with T1/2= 4.2 h, J = 9/2 decays by 100 % EC+β+ to the ground state of 109Cd. There are two isomeric states 109m1,m2 In with T1/2= 1.34 m and T1/2= 0.21 s respectively both decay by 100 % IT to their ground state 109gIn. Also the radioisotope 109Sn with + 109g T1/2= 18 m decays by 100 % EC+β to the ground state In. Therefore, measurements obtained several hours after EOB represent total 109g cumulative production of In. We used the two gamma lines Eγ= 203.5 keV, Iγ= 74 % and Eγ= 426.25 keV, Iγ= 4.12 % from the decay scheme of 109gIn in the cross section calculation.

Two channels contribute to the formation of 109gIn; 108Cd(3He,np) and 110Cd(3He,3np). There is no previous available experimental data for this reaction. The cross section values and their errors for the formation of 109gIn are presented in Table 4.14.

The excitation function shows a broad peak with maximum of about 9.3 mb at 21.8 MeV Fig. 4.15.

ALICE code for total formation has lower values than the experimental values. The code represents about 28 % of the experimental with more or less the same behavior. ALICE code for the ground state

Chapter Four Results and Discussion formation only represents about 25 % of the experimental data with somehow the same trend. EMPIRE code has different behavior from the experimental with lower cross section values. TALYS and TENDL match well each other while they have different behavior from the experimental data.

Table. 4.14 Measured cross sections and their errors for natCd(3He,x)109gIn.

Energy (MeV) Cross section (mb) 26.36±0.30 6.96±0.89 24.81±0.37 8.48±1.00 23.45±0.43 9.22±1.28 21.76±0.51 9.30±1.78 19.97±0.59 8.65±1.32 18.01±0.68 5.01±0.92 16.01±0.77 1.69±0.54 13.76±0.87 0.08±0.02

14 This work 12 ALICE 109g+mIn ALICE 109gIn 10 EMPIRE TALYS 8 TENDL 6

Cross section section Cross (mb) 4 natCd(3He,x)109 cumIn

0 12 14 16 18 20 22 24 26 28 3He -particle energy (MeV)

Fig. 4.15 Excitation function of the natCd(3He,x)109gIn reaction.

Chapter Four Results and Discussion 108g 4.2.9 FORMATION OF In

108g π + The ground state In with T1/2= 58 m, J = 7 decays by 100 % EC+β+ to the sTable nuclide 108Cd. The cross section were assessed by using three gamma lines; Eγ= 242.75 keV, Iγ= 41 %, Eγ= 1032.92 keV, Iγ= 35 % and Eγ= 1056.97 keV, Iγ= 29 %.

Two channels contribute to the production of 108gIn namely 106Cd(3He,p) and 108Cd(3He,2np). There is no previous available experimental data for this reaction. The cross section values and their errors for the formation of 109gIn are presented in Table 4.15.

Table. 4.15 Measured cross sections and their errors for natCd(3He,x)108gIn.

Energy (MeV) Cross section (mb) 26.36±0.30 2.01±0.30 24.81±0.37 1.52±0.22 23.45±0.43 0.90±0.16 21.76±0.51 0.42±0.10 19.97±0.59 0.17±0.01 18.01±0.68 0.15±0.02 16.01±0.77 0.04±0.02

The excitation function raises firstly slowly up to about 20 MeV and then increases rapidly to a maximum of 2 mb at 26.4 MeV Fig. 4.16.

ALICE code data for the total cross section equals twice as the excremental data. On the other hand ALICE code for the ground state matches more or less the experimental results in trend and magnitudes. EMIRE code results are in fair agreement to the experimental results especially over 20 MeV. TALYS and TENDL match well each other with higher values than the present values. Their results are shifted to the low energy range by about 4 MeV.

Chapter Four Results and Discussion

3 This work ALICE 108g+mIn 2.5 ALICE 108gIn EMPIRE 2 TALYS TENDL 1.5

1 Cross section section (mb) Cross

0.5 natCd(3He,x)108gIn

0 12 14 16 18 20 22 24 26 28 30 3He -particle energy (MeV)

Fig. 4.16 Excitation function of the natCd(3He,x)108gIn reaction.

107g 4.2.10 FORMATION OF In

107 π + The ground state of In with T1/2= 32.4 m, J = 9/2 decays by 100 % EC+β+ to 107Cd. The production of 107gIn from natural cadmium is 107m cumulative since the isomeric state In with T1/2= 50.4 s decays by 100 107 + IT and the radio nuclide Sn with T1/2= 2.9 m decays by 100 % EC+β to the ground state of 107In. we evaluate the cross section of the 107gIn by using three gamma lines at Eγ= 204.97 keV, Iγ= 47 %, Eγ= 320.92 keV, Iγ= 10.2 % and Eγ= 505.51 keV, Iγ= 11.9 %.

Two channels contribute to the formation of 107gIn; 106Cd(3He,np) and 108Cd(3He,3np). There is no previous available experimental data for this reaction. The cross section values and their errors for the formation of 107gIn are presented in Table 4.16.

The excitation function shows a peak with a maximum of about 11.9 mb at 23.5 MeV Fig. 4.17.

ALICE code data for the total cross section has the same trend of the experimental. The code represents about 70 % of the experimental values over 18 MeV. The ALICE code for the ground state only has also the same trend of the experimental excitation function. The code

Chapter Four Results and Discussion represents about 50 % of the experimental. EMPIRE code results are too low. TALYS and TENDL match also each other with different shape from the excitation function. Their values are lower than the experimental values.

Table. 4.16 Measured cross sections and their errors for natCd(3He,x)107gIn.

Energy (MeV) Cross section (mb) 26.36±0.30 7.93±1.27 24.81±0.37 11.28±1.49 23.45±0.43 11.86±1.50 21.76±0.51 10.89±1.34 19.97±0.59 9.61±1.17 18.01±0.68 6.42±0.79 16.01±0.77 1.35±0.29 13.76±0.87 0.01±0.04

14 This work ALICE 107g+mIn 12 ALICE 107gIn EMPIRE 10 TALYS TENDL 8

6 natCd(3He,x)107 cumIn

4 Cross section section (mb) Cross

0 10 12 14 16 18 20 22 24 26 28 30 3He -particle energy (MeV)

Fig. 4.17 Excitation function of the natCd(3He,x)107gIn reaction.

100

Chapter Four Results and Discussion 4.3. EXCITATION FUNCTIONS OF CADMIUM ISOTOPES

115g 4.3.1 FORMATION OF Cd

115 π + Cd has a ground state with T1/2= 53.46 h, J = 1/2 decays by 100 - 115 π - % β to In and an isomeric state with T1/2= 44.6 d, J = 11/2 decays also by 100 % β- to 115In. We assisted the cross section of the ground state using two independent gamma lines at Eγ= 492.3 MeV, Iγ= 8.03 % and Eγ= 527.9 MeV, Iγ= 27.45 %. On the other hand the isomeric state decay scheme has a set of week gamma lines that couldn’t detected in our spectra.

Table. 4.17 Measured cross sections and their errors for natCd(3He,x)115gCd.

Energy (MeV) Cross section (mb) 26.36±0.30 11.54±2.01 24.81±0.37 10.71±2.01 23.45±0.43 9.68±1.79 21.76±0.51 9.41±1.60 19.97±0.59 9.47±1.66 18.01±0.68 5.55±0.85 16.01±0.77 0.86±0.25 13.76±0.87 0.31±0.13

Two channels contribute to the production of 115Cd via the reactions 114Cd(3He,2p) and 116Cd(3He,2n2p). The measured cross section values and their errors for the 117mSn formation are presented in Table 4.17.

The excitation function increases with the energy up to a maximum of 11.5 mb at 26.4 MeV. The excitation function has a hump at about 20 MeV with a maximum of 9.5 mb Fig. 4.18.

101

Chapter Four Results and Discussion [Montgomery and Porile, 1969] irradiated 97.2 % enriched 116Cd with 3He ions in the energy range 33-13 MeV. They calculated the cross section for 115gCd using the same gamma lines that used in this work and also calculated the cross section for 115mCd using β- detection. The present results equal to the sum of the ground and isomeric state cross sections of [Montgomery and Porile, 1969] without normalizing their data to the national abundance. Their ground state cross section represents about 60 % of the present data also without normalization. They showed that the 116Cd(3He,α) reaction proceeds predominantly by a direct process presumably a pick up process.

20 This work 18 Montgometry & Porile 115m+gCd ALICE 115g+mCd *10 16 ALICE 115gCd *10 14 EMPIRE *100 TALYS *10 12 TENDL *10 10

8 natCd(3He,x)115gCd

6 Cross section section (mb) Cross 4 2 0 10 12 14 16 18 20 22 24 26 28 30 32 3He -particle energy (MeV)

Fig. 4.18 Excitation function of the natCd(3He,x)115gCd reaction.

All the theoretical codes have different behavior from the experimental data and even have low values.

111m 4.3.2 FORMATION OF Cd

111 π - The isomeric state of Cd with T1/2= 48.54 m, J = 11/2 decays by 100 % IT through two gamma lines at Eγ= 150.82 keV, Iγ= 29.1 % and 111m Eγ= 245.4 keV, Iγ= 94 %. We evaluated the cross section of Cd using only the independent gamma line at Eγ= 150.82 keV since the second line 111 is common with a line in the decay scheme of the longer lived In (T1/2= 2.8 d). As 111In decays by 100 EC to 111mCd, the production of this

102

Chapter Four Results and Discussion isomeric state should be a cumulative process. However, the contribution to the isomeric state production from 111In is a very small fraction of about 0.012 %, and hence can be neglected.

Many channels participate in 111mCd production; 110Cd(3He,2p), 111Cd(3He,n2p), 112Cd(3He,2n2p) and 113Cd(3He,3n2p). There is no previous available experimental data for this reaction. The cross section values and their errors for the formation of 107gIn are presented in Table 4.18.

Table. 4.18 Measured cross sections and their errors for natCd(3He,x)111mCd.

Energy (MeV) Cross section (mb) 26.36±0.30 8.30±1.11 24.81±0.37 8.01±1.01 23.45±0.43 6.43±0.86 21.76±0.51 4.01±0.59 19.97±0.59 3.35±0.49 18.01±0.68 1.96±0.31 16.01±0.77 0.36±0.13

The excitation function increases continuously to a maximum cross section about 8.3 mb at 26.4 MeV Fig. 4.19. The complexity of the excitation function may indicate the different channels contributing to the 111mCd formation from different target isotopes.

ALICE code for the total cross section has more or less the same behavior of the experimental data. The code results represent about 50 % of the experimental. ALICE code for only the isomeric state cross section has also the same behavior of the experimental with lower values. EMPIRE code results are higher than the present work with different behavior. TALYS and TENDL match each other with different shape from the excitation function.

103

Chapter Four Results and Discussion

10 This work 9 ALICE 111g+mCd 8 ALICE 111mCd 7 EMPIRE 6 TALYS TENDL 5 4 natCd(3He,x)111mCd

3 Cross section section Cross (mb) 2 1 0 10 12 14 16 18 20 22 24 26 28 3He -particle energy (MeV)

Fig. 4.19 Excitation function of the natCd(3He,x)111mCd reaction.

4.4. ISOMERIC CROSS SECTION RATIOS

In a given reaction the ratio between the isomeric cross section and the total (ground and isomeric) cross section σm/σm+σg is called the isomeric cross section ratio. Its plot as a function of energy can indicate several aspects of nuclear structure and nuclear reaction theories. The isomeric cross section ratio is dependent on the spins of the two states concerned [Qaim et al., 1990]. In this work we presented the isomeric cross section ratio for two isomer pairs, namely 117m,gIn and 110m,gIn. The experimental ratio and theoretical calculated ratio using EMPIRE and TALYS codes are described below.

4.4.1 ISOMERIC CROSS SECTION RATIO OF 117m,gIn

As discussed earlier, 117m,gIn pair can be formed via the reactions (3He,np) and/or (3He,d). The ground state has higher spin value (9/2) than the isomeric state (1/2). The ground state has also higher cross section values than the isomeric state.

104

Chapter Four Results and Discussion

The isomeric cross section ratio for 117In isomer pair is plotted as a function of the energy Fig. 4.20 and the data are presented in Table 4.19.

The isomeric cross section ratio shows a small variation in the isomeric ratio nearly over the interested energy range. The ratio varies between 0.23 and 0.35 from 27 to 16 MeV respectively. This means that as the energy increases the reaction doesn’t favors the formation of the high spin state (the ground state). Thus the probability of formation of the high spin isomer remains constant while the energy increases. This is the behavior of direct reaction mechanism since in direct interactions the isomeric ratio is known to be small and relatively insensitive to the bombarding energy. That is because most of the angular momentum is carried off by the emitted particles [Montgomery and Porile, 1969].

Table. 4.19 Isomeric cross section ratio in the 116Cd(3He,np)117m,gIn process.

Energy (MeV) σm/(σm+σg) 26.36 0.23 24.81 0.23 23.45 0.23 21.76 0.24 19.97 0.24 18.01 0.28 16.01 0.35

Therefore the 117In formation reaction proceeds predominantly by a direct process. The process is one nucleon (proton) transfer reaction.

In the energy range 20-16 MeV the ratio slightly decreases from 0.35 to 0.24 respectively. This decrease is small enough to be neglected in the analysis but it may be considered corresponding to a slight increase of the high spin formation probability and hence corresponding to preequilibrium process.

105

Chapter Four Results and Discussion EMPIRE code results match well the experimental results in trend with lower values. TALYS code has more or less the same behavior especially in the energy 20-27 MeV with higher values.

0.45 116Cd(3He,np)117Inm,g

0.35

)

+ g

σ 0.25

/ ( /

m σ

0.15 This work EMPIRE TALYS 0.05 15 17 19 21 23 25 27 3He -particle energy (MeV)

Fig. 4.20 Isomeric cross section ratio for the isomeric pair 117m,gIn.

4.4.2 ISOMERIC CROSS SECTION RATIO OF 110m,gIn

110In is formed via a combination of many processes mainly 108Cd(3He,p), 110Cd(3He,2np) and 111Cd(3He,3np). The ground state has again higher spin value (7) than the isomeric state (2). The ground state has lower cross section values than the isomeric state.

The isomeric cross section ratio for 110In isomer pair is plotted as a function of the energy Fig. 4.21 and the data are presented in Table 4.20.

The isomeric cross section ratio decreases from 0.93 at about 27 MeV to 0.74 at 28MeV. Hence, as the energy increases the formation of the ground state (the highest spin level) become much preferred. Although the isomeric cross section is higher than that for the ground state at all energies, the probability of formation of the ground state increases with the energy. This is the same behavior of compound nuclear mechanisms because of the greater angular momentum

106

Chapter Four Results and Discussion transferred to the compound nucleus which in turn favors the formation of the high spin nuclide.

Table. 4.20 Isomeric cross section ratio in the natCd(3He,x)110m,gIn process.

Energy (MeV) σm/(σm+σg) 26.36 0.74 24.81 0.77 23.45 0.80 21.76 0.85 19.97 0.92 18.01 0.93

Because there are many channels that may contribute to the formation of 110In including nucleon and cluster emission we couldn’t assure that the reaction mechanism is compound but we could say that the formation of 110In may proceed by a compound process.

EMPIRE and TALYS have more or less the same behavior of the experimental ratio with lower values.

1.1 natCd(3He,x)110m,gIn This work 1 TALYS 0.9 EMPIRE

) 0.8

m σ

+ 0.7 g

σ 0.6

/ ( / m

σ 0.5 0.4 0.3 0.2 17 18 19 20 21 22 23 24 25 26 27 28 3He -particle energy

Fig. 4.21 Isomeric cross section ratio for the isomeric pair 110m,gIn.

107

Chapter Four Results and Discussion 4.5. YIELD CALCULATIONS

Integral yields were calculated in MBq/ µA.h from the trend curves of the excitation functions for 109,110m,110g,111.113m,114m,115m,117mIn, 110,111,113,117mSn and 115Cd produced in 3He induced reactions on natCd (Figs. 4.22,23,24). It refers to the so called physical yield (instantaneous irradiation).

The most medically important isotopes of the isotopes of interest are 111,114mIn. The longer lived 114mIn (49.51 d) has low integral yield amount to be 0.053 MBq/ µA.h in the energy range 27→12 MeV due to its long half live.

On the other hand, 111In with (2.81 d) which has the highest cross section values in the interested reactions has integral yield 2.83 MBq/ µA.h over the energy range 27→10 MeV. [Nakamura et al., 1979] found that the helium-3 reactions gave higher 111In yield than alpha reactions on natural cadmium. 111In integral yield at the 3He-particle energy of 40 MeV amounted to be 270 µCi/ µA.h (≈ 9.99 MBq/ μA.h).

111Sn, 113mIn, and 110mIn isotopes have the highest integral yield due to their high cross sections and short half lives. The integral yield of 111Sn over the energy range 27→15.3 MeV amounts to be 97.97 MBq/ μA.h. The integral yield of 113mIn over the energy range 27→4 MeV amounts to be 22.19 MBq/ µA.h, while that of 110mIn over the energy range 27→17.3 MeV amounts to be 28 MBq/ µA.h. However, enriched 110Cd can be used to produce 110mIn through an 110Sn→110mIn generator; batch yields of >20 mCi 110Sn allow to run a clinical 110Sn→110mIn generator for the whole day. Also using highly enriched 113Cd, the radionuclide 113mIn can be produced via the 113Cd(3He,3n)113Sn→113mIn process [Frank Rösch et al., 1997].

110Sn, 109In, and 115mIn have almost equal and significantly high integral yields. The integral yield of 115mIn amounts to be 7.55 MBq/ μA.h over the energy range 27→10 MeV while that of 109In amounts to be 8.98 MBq/ μA.h over the same energy range.

The integral yield of 110Sn over the energy range 27→12 MeV amounts to be 9.18 MBq/ μA.h. In the case of natCd targets weighing

108

Chapter Four Results and Discussion about 200 mg (foil diameter 13 mm, foil thickness 0.14 mm), the yield of 110Sn amounted to ≈ 9 MBq/ μA.h [Frank Rösch et al., 1997]. An extrapolation to 100 % enrichment of 110Cd resulted in 110Sn yield of about 75 MBq/ μA.h. [Frank Rösch et al., 1997] used 36→25 MeV 3He induced nuclear reactions on 91.5 % enriched 110Cd as target material to get a high 110Sn yield of 81 MBq/ µA.h and then produced 110mIn from 110Sn→110mIn generator. [Szelecsényi et al., 1991] calculated the thick target yield of 110Sn over the energy range 27→16.3 MeV. Their calculated yield was 180 μCi/ μA.h ≈ 6.7 MBq/ μA.h.

The integral yield of 117mIn over the energy range 27→4 MeV amounts to be 2.5 MBq/ μA.h and that of 110In amounts to be 1.8 MBq/ μA.h over the energy range 27→18 MeV. The integral yield of 115Cd amounts to be 0.18 MBq/ μA.h over the energy range 27→1 MeV.

113Sn integral yield amounts to be 0.05 MBq/ μA.h over the energy range 27→12 MeV. The calculated integral yield of 117mSn amounts to 0.007 MBq/ μA.h over the energy range 27→1 MeV. [Qaim and Döhler, 1984] irradiated natural cadmium by 120 MeV 3He and found that the thick target yield of 113Sn amounts to be ≈ 0.44 MBq/ μA.h over the energy 115→5 MeV and that of 117mSn amounts to be ≈ 0.074 MBq/ μA.h over the energy range 114→2 MeV.

Alpha induced nuclear reactions on natCd often have lower cross section and integral yield values than 3He reactions. Only 108,109In and 113,117mSn cross section values obtained by alpha induced reactions are higher than that obtained by 3He reactions; see [Hermanne et al., 2010; Nakamura et al., 1979; Qaim and Döhler, 1984].

Proton and deuteron induced nuclear reactions on natural and enriched cadmium have higher integral yields than 3He reactions; see [Khandaker et al., 2005; Otozai et al., 1966; Tárkányi et al., 1994; Tárkányi et al., 2005; Tárkányi et al., 2006, 2007]. These routes are already the standard production routes for our interested isotopes.

109

Chapter Four Results and Discussion

1.E+02 110 Sn 1.E+01 111Sn 1.E+00 113 Sn 1.E-01 117mSn 1.E-02 115Cd 1.E-03 1.E-04 1.E-05 1.E-06

Int0 Yield (MBq/µA0h)Yield Int0 1.E-07 1.E-08 0 3 6 9 12 15 18 21 24 27 30 3He -particle energy (MeV)

Fig. 4.22 Integral yields of natCd(3He,x)110,111,113,117mSn and 115Cd reactions.

1.E+1

1.E-2

1.E-5

117m In 1.E-8 115m In

114m In Int0 Yield (MBq/µA0h) Yield Int0 1.E-11 113m In 111 In

1.E-14 3 6 9 12 15 18 21 24 27 30 3He -particle energy (MeV)

Fig. 4.23 Integral yields of natCd(3He,x)111,113m,114m,115m,117mIn reactions.

110

Chapter Four Results and Discussion

1.E+2 1.E+1 1.E+0 1.E-1 1.E-2 1.E-3 1.E-4 1.E-5 110 In

1.E-6 110m In Int0 Yield (MBq/µA0h) Yield Int0 1.E-7 109 In 1.E-8 1.E-9 9 11 13 15 17 19 21 23 25 27 29 3He -particle energy (MeV)

Fig. 4.24 Integral yields of natCd(3He,x)109,110m,110In reactions.

111

Conclusion

CONCLUSION

Conclusion In this work 3He induced nuclear reactions on natural cadmium were studied up to 27 MeV. The excitation functions for the production of the radionuclides 117m,113,111,110Sn, 117m,g,116m,115m,114m,113m,111,110m,g,109,108,107In and 115,111mCd were calculated. Most of these reactions provide the first consistent sets of data in this energy range.

The present experimental data were compared with the previously available experimental data. The experimental data of [Szelecsényi et al., 1991] describes the present experimental data of 111Sn but slightly differs from the present 110Sn data. [Qaim and Döhler, 1984] data matches the present data of 113Sn but has lower values in the case of 117mSn. The data calculated by [Montgomery and Porile, 1969] describes more or less the present data of 117mSn and defers completely from the present data of 115Cd. We didn’t find data in the literature for the production of indium isotopes via irradiation of cadmium by 3He.

The excitation function of the reaction natCd(3He,x)111Sn may be used as a monitor reaction for the 3He beams in this energy range.

The physical integral yields were calculated for the isotopes 110,111,113,117mSn, 109,110m,g,111,113m,114m,115m,117mIn and 115Cd. The plotted curves of the integral yields showed that a chemical separation is a must for any isotope to be produced. Also highly enriched cadmium isotopes could be used to give high production yields.

The classical production routes for the interested radioisotopes are proton or deuteron induced reactions on natural or enriched cadmium or tin targets. The low cross section values of the present data compared to that of proton and deuteron induced reactions data in addition to the poor availability of 3He beams, the high cost of the 3He ions and its low beam intensity make 3He induced reactions for isotope production importance only if they are the only possible routes. On the other hand, comparing to alpha induced reactions the production of the interested isotopes by 3He induced reactions often have higher yields. Therefore the standard classical routes are still most preferred.

The experimental data were compared also to theoretical calculated data using ALICE-IPPE, EMPIRE-03, TALYS-1.2 and the nuclear reaction data library TENDL. In general all the theoretical nuclear reaction models couldn’t describe the experimental results. This may be indicate

112

Conclusion that the formation of almost all interested isotopes have contributions from pick up and/or transfer direct reaction mechanisms due to the loosely bound projectile 3He. These mechanisms were not included in the theoretical calculations. The poor data of 3He induced reactions is also a principal reason for the disagreement between the experimental and theoretical results.

The isomeric cross section ratios for the isomeric pairs 117m,gIn and 110m,gIn were calculated and plotted as a function of the 3He energy. In the case of the isomeric pair 117m,gIn i.e. (3He,np) and/or (3He,d) reactions there is only a small variation in the isomeric ratio over the energy range of interest. This is the behavior of direct reaction mechanism namely charge transfer reaction. But in the case of the second isomeric pair viz. 110m,gIn, the decreasing of the isomeric ratio with increasing the energy indicates that the probability of formation of the high spin state (the ground state) increases with the energy. This is the behavior of compound nuclear reaction mechanisms.

113

References

REFERENCES

References REFERENCE

Akkermans, J. M. and Gruppelaar, H. (1985): “Analysis of Continuum Gamma-Ray Emission in Precompound Decay Reactions”. Physics Letters B, V. 157, pp. 95. Al-Abyad, M. (2003): “Nuclear Reactions Studies on Some Natural Targets Using Cyclotron”. M.Sc. Thesis, Faculty of Science, Ain Shams University, Egypt. Axel, P. (1962): “Electric Dipole Ground-State Transition Width Strength Function and 7-MeV Photon Interactions”. Physical Review, V. 126, pp. 671. Basdevant, J. L.; Rich, J. and Spiro, M. (2005): “Fundamentals in Nuclear Physics: From Nuclear Structure to Cosmology”. Springer Science+Business Media, Inc. New York, USA. Bĕták, E. and Dobes, J. (1979): “Gamma Emission in the Preequilibrium Exciton Model”. Physics Letters B, V. 84, pp. 368. Bĕták, E. and Oblŏzinský, P. (1993): “Code PEGAS: Preequilibrium Exciton Model with Spin Conservation and Gamma Emission”. Technical Report INDC(SLK)-001, IAEA/Slovak Academy of Sciences. Blann, M. (1972): “Importance of the Nuclear Density Distribution on Preequilibrium Decay”. Physical Review Letters, V. 28, pp. 757. Blann, M. (1975): “Pre-equilibrium Decay”. Annual Review of Nuclear Science, V. 25, pp. 123. Blann, M. (1991): “Recent Progress and Current Status of Preequilibrium Theories and Computer Code ALICE”. UCRL-JC- 109052. Blann, M. (1996): “New Precompound Decay Model”. Physical Review C, V. 54, pp. 1341. Blann, M. and Chadwick, M. B. (1998): “New Precompound Model: Angular Distributions”. Physical Review C, V. 57, pp. 233.

114

References Blann, M. and Mignerey, A. (1972): “Preequilibrium Decay at Moderate Excitations and the Hybrid Model”. Nuclear Physics A, V. 186, pp. 245. Blann, M. and Vonach, H. K. (1983): “Global Test of Modified Precompound Decay Models”. Physical Review C, V. 28, pp. 1475. Blokhin, A. I.; Ignatyuk, A. V.; Pashchenko, A. B.; Sokolov, Yu. V. and Shubin, Yu. N. (1985): “Analysis of Threshold Reaction Excitation Functions in Frame of Unified Superfluid Model”. Community Academy of Science of USSR, V. 49, pp. 962. Brink, D. M. (1957): “Individual Particle and Collective Aspects of the Nuclear Photoeffect”. Nuclear Physics, V. 4, pp. 215. Byun, S. H. (2010): “Radiation and Radioisotope Methodology” Educational Course in McMaster University, Available from URL . Capote, R.; Herman, M.; Oblozinsky, P.; Young, P. G.; Goriely, S.; Belgya, T.; Ignatyuk, A. V.; Koning, A. J.; Hilaire, S.; Plujko, V.; Avrigeanu, M.; Bersillon, O.; Chadwick, M. B.; Fukahori, T.; Kailas, S.; Kopecky, J.; Maslov, V. M.; Reffo, G.; Sin, M.; Soukhovitskii, E.; Talou, P.; Yinlu, H. and Zhigang, G. (2009): “RIPL: Reference Input Parameter Library for Calculation of Nuclear Reactions and Nuclear Data Evaluation”. Nuclear Data Sheets, V. 110, pp. 3107. Cline, C. K. (1972): “Extensions to the Preequilibrium Statistical Model and A Study of Complex Particle Emission”. Nuclear Physics A, V. 193, pp. 417. Cline, C. K. and Blann, M. (1971): “The Preequilibrium Statistical Model: Description of the Nuclear Equilibration Process and Parameterization of the Model”. Nuclear Physics A, V. 172, pp. 225. Contemporary Physics Education Project (CPEP) (2003): “Nuclear Science Materials”. Guide to the Nuclear Science Wall Chart, Available from URL < http://www.lbl.gov/abc/wallchart/>.

115

References Das, A. and Ferbel, T. (2003): “Introduction to Nuclear and Particle Physics”. 2nd Edition, World Scientific Publishing Co. Pte. Ltd. Singapore. Dityuk, A. I.; Konobeyev, A. Yu.; Lunev, V. P. and Shubin, Yu. N. (1998): “New advanced version of computer code ALICE-IPPE”. INDC (CCP)-410, IAEA, Vienna. Ehrhardt, G. J.; Wynn Volkert, Goeckeler, W. F. and Kapsch, D. N. (1983): “A New Cd-115→In-115m Radionuclide Generator”. Journal of Nuclear Medicine, V. 24, pp. 349. Ekstrom, L. P. and Firestone, R. B. (2000): “The Berkeley Laboratory Isotopes Project’s Exploring the Table of Isotopes” Available from URL . Frank Rösch; Qaim, S. M.; Novgorodov, A. V. and Tsai, Y. M. (1997): “Production of Positron-emitting 110mIn Via the 110Cd(3He,3n)110Sn→110mIn Process”. Journal of Applied Radiation and Isotopes, V. 48, pp. 19. Galchuk, A. V. (1995): “The Functioning of the MGC-20 Cyclotron Equipment”. Lecture in Cyclotron Manual. Gilbert, A. and Cameron, A. G. W. (1965): “A Composite Nuclear- Level Density Formula with Shell Corrections”. Canadian Journal of Physics, V. 43, pp. 1446. Gregory, R. C.; Jan-Olov, L. and Jan, R. (2002): “Radiochemistry and Nuclear Chemistry”. 3rd Edition, Butterworth-Heinemann, USA. Griffin, J. J. (1966): “Statistical Model of Intermediate Structure”. Physical Review Letters, V. 17, pp. 478. Herman, M. (2001): “Overview of Nuclear Reaction Models Used in Nuclear Data Evaluation”. Journal of Radiochemica Acta, V. 89, pp. 305. Herman, M.; Capote, R.; Carlson, B. V.; Obložinský, P.; Sin, M.; Trkov, A.; Wienke, H. and Zerkin, V. (2007): “EMPIRE: Nuclear Reaction Model Code System for Data Evaluation”. Nuclear Data Sheets, V. 108, pp. 2655.

116

References Hermanne, A.; Daraban, L.; Adam Rebeles, R.; Ignatyuk, A.; Tárkányi, F. and Takács, S. (2010): “Alpha Induced Reactions on natCd up to 38.5 MeV: Experimental and Theoretical Studies of the excitation functions”. Journal of Nuclear Instruments and Methods in Physics Research B, V. 268, pp. 1376. Hofmann, H. M.; Richert, J.; Tepel, J. W. and Weidenmuller, H. A. (1975): “Direct Reactions and Hauser–Feshbach Theory”. Annals of Physics, V. 90, pp. 403. Hussain, M. (2009): “Evaluation of Nuclear Reaction Cross Sections Relevant to the Production of Emerging Therapeutic Radionuclides 103Pd, 186Re and 67Cu”. Ph.D. Thesis, Department of Physics, Government College University, Lahore, Pakistan. Hussein, M. S. and Rego, R. A. (1983): “Statistical Features of Pre- Compound Processes in Nuclear Reactions”. Revista Brasileira de fisica, V. 13, pp. 143. Ignatyuk, A. V. (1975): “Contribution of Collective Modes to Level Density of Excited Nuclei”. Yadernaya Fizika, V. 21, pp. 20. ISO (1995): “Guide to Expression of Uncertainty in Measurement”. International Organization for Standardization, Geneva. Iwamoto, A. and Harada, K. (1982): “Mechanism of Cluster Emission in Nucleon-Induced Preequilibrium Reactions”. Physical Review C, V. 26, pp. 1821. Joseph Magill and Jean Galy (2005): “Radioactivity Radionuclides Radiation”. Springer-Verlag, Berlin Heidelberg, Germany. Kalbach, C. (1977): “The Griffin Model, Complex Particles and Direct Nuclear Reactions”. Zeitschrift für Physik A: Hadrons and Nuclei, V. 283, pp. 401. Kalbach, C. (2005): “Pre-equilibrium Reactions with Complex Particle Channels”. Physical Review C, V. 71, pp. 034606. Kaplan, I. (1963): “Nuclear Physics”. 2nd Edition, Addison-Wesley Publishing Company, Inc. USA.

117

References Khandaker, M. U.; Kim, K.; Lee, M. W.; Kim, K. S.; Kim, G. N.; Cho, Y. S. and Lee, Y. O. (2008): “Production Cross-Sections for the Residual Radionuclides from the natCd(p,x) Nuclear Processes”. Journal of Nuclear Instruments and Methods in Physics Research B, V. 266, pp. 4877. Knoll, G. F. (2000): “Radiation Detection and Measurement” 3rd Edition, John Wiley & Sons, Inc. New York, USA. Koning, A. J. and Delaroche, J. P. (2003): “Local and Global Nucleon Optical Models from 1 keV to 200 MeV”. Nuclear Physics A, V. 713, pp. 231. Koning, A. J. and Duijvestijn, M. C. (2004): “A Global Pre- equilibrium Analysis from 7 to 200 MeV Based on the Optical Model Potential”. Nuclear Physics A, V. 744, pp. 15. Koning, A. J. and Duijvestijn, M. C. (2006): “New Nuclear Data Evaluation for Ge Isotopes”. Journal of Nuclear Instruments and Methods in Physics Research B, V. 248, pp. 197. Koning, A. J.; Hilaire, S. and Duijvestijn, M. C. (2009): “TALYS-1.2: A Nuclear Reaction Program”. User Manual. Koning, A. J.; Hilaire, S. and Duijvestijn, M. C. (2005): “TALYS: Comprehensive Nuclear Reaction Modeling”. American Institute of Physics Conference Proceedings, V. 769, pp. 1154. Kopecky, J.; Uhl, M. and Chrien, R. E. (1993): “Radiative Strength in the Compound Nucleus 157Gd”. Physical Review C, V. 47, pp. 312. Krane, K. S. (1988): “Introductory Nuclear Physics”. 2nd Eddition, John Wiley & Sons, inc. New York, USA. L’Annunziata, M. F. (2003): “Handbook of Radioactivity Analysis”. 2nd Edition, Academic press. USA. Leo, W. R. (1992): “Techniques for Nuclear and Particle Physics Experiments: A How to Approach” 2nd Edition, Springer-Verlag, Berlin Heidelberg, Germany.

118

References Liburdy, R. P.; David Hunter; Wyant, A. R. and Tatsch, R. E. (1980): “Indium-114m in Dual-Nuclide Studies with Cr-51: Comparison with Indium-111”. Journal of Nuclear Medicine, V. 21, pp. 992. Liverhant, S. E. (1960): “Elementary Introduction to Nuclear Reactor Physics”. John Wiley & Sons, Inc. USA. Maher, K. (2006): “Basic Physics of Nuclear Medicine”. A Featured Wekebook, Available from . Mark Lubberink; Vladimir Tolmachev; Charles Widström; Alexander Bruskin; Hans Lundqvist and Jan-Erik Westlin (2002): “110mIn-DTPA-D-Phe1-Octreotide for Imaging of Neuroendocrine Tumors with PET”. Journal of Nuclear Medicine, V. 43, pp. 1391. Martin, B. R. (2006): “Nuclear and Particle Physics: An Introduction”. John Wiley & Sons, Ltd. Chichester, England. Meyerhof, W. E. (1967): “Elements of Nuclear Physics”. McGraw-Hill, Inc. USA. Michael, P. and Leo, M. L. N. (2007): “Radionuclide Concentrations in Food and the Environment”. Taylor & Francis Group, LLC. Boca Raton, USA. Milazzo-Colli, L. and Braga-Marcazzan, G. M. (1973): “α-Emission by Preequilibrium Processes in (n,α) Reactions”. Nuclear Physics A, V. 210, pp. 297. Milocco, A.; Trkov, A. and Capote, R. (2011): “Nuclear Data Evaluation of 55Mn by the EMPIRE Code with Emphasis on the Capture Cross Section”. Nuclear Engineering and Design, V. 241, pp 1071. Montgomery, D. M. and Porile, N. T. (1969): “Reactions of 116Cd with Intermediate Energy 3He and 4He Ions”. Nuclear Physics A, V. 130, pp. 65.

119

References Mughabghab, S. F. and Dunford, C. L. (2000): “A Dipole-Quadrupole Interaction Term in E1 Photon Transitions” Physics Letters B, V. 487, pp. 155. Nakamura, Y.; Nakahara, H. and Murakami, Y. (1979): “Formation of Indium-111 in Alpha and Helium-3 Bombardment of Natural Cadmium”. Radioisotopes, V. 28, pp. 675. Naoki Tajima (2001): “Hartree-Fock+BCS Approach to Unstable Nuclei with the Skyrme Force”. Progress of Theoretical Physics Supplement, No. 142, pp. 265. Nishioka, H.; Verbaarschot, J. J. M.; Weidenmüller, H. A. and Yoshida, S. (1986): “Statistical Theory of Precompound Reactions: The Multistep Compound Process” Annals of Physics, V. 172, pp. 67. NUDAT2 database: National Nuclear Data Center, Available from URL . Otozai, K.; Kume, S.; Mito, A.; Okamura, H.; Tsujino, R.; Kanchiku, Y.; Katoh, T. and Gotoh, H. (1966): “Excitation Functions for the Reactions Induced by Protons on Cd up to 37 MeV”. Nuclear Physics, V. 80, pp. 335. Plujko, V. A. (2000): “A New Closed-Form Thermodynamic Approach for Radiative Strength Functions”. ACTA Physica Polonica B, V. 31, pp. 435. Pluyko, V. and Prokopets, G. (1978): “Emission of γ-Rays in the Exciton Model”. Physics Letters B, V. 76, pp. 253. Podgoršak, E. B. (2006): “Radiation Physics for Medical Physicists”. Springer-Verlag, Berlin Heidelberg, Germany. Powsner, R. A. and Powsner, E. R. (2006): “Essential Nuclear Medicine Physics”. 2nd Edition, Blackwell Publishing Ltd. USA. Qaim, S. M. and Döhler, H. (1984): “Production of carrier-free 117mSn”. International Journal of Applied Radiation and Isotopes, V. 35, PP. 645.

120

References Qaim, S. M.; Ibn-Majah, M.; Wölfle, R. and Strohmaier, B. (1990): “Excitation Functions and Isomeric Cross-Section Ratios for the 90Zr(n,p)90Ym,g and 91Zr(n,p)91Ym,g Processes”. Physical Review C, V. 42, pp. 363. Raymond, L. M. (2009): “Nuclear Energy: An Introduction to the concepts, systems, And Applications of Nuclear Processes”. 6th Edition, Elsevier Inc. USA. Raynal, J. (1994): “Notes on ECIS94”. Saclay Report CEA-N 2772, France. Raynal, J. (2005): “ECIS06 code”. NEA-0850 Data Bank, Paris, France. Rayudu, G. V. S.; Shirazi, S. P. H.; Fordham, E. W. and Friedman, A. M. (1973): “Comparison of the Use of 52F and 111In for Hemopoietic Marrow Scanning”. Journal of Applied Radiation and Isotopes, V. 24, pp. 451. Reimer, P. (2002): “Fast Neutron Induced Reactions Leading to Activation Products: Selected Cases Relevant to Development of Low Activation Materials, Transmutation and Hazard Assessment of Nuclear Wastes”. Ph.D. Thesis, Faculty of Natural Sciences, University of Cologne, Germany. Rittersdorf, I. (2007): “Gamma Ray Spectroscopy: Nuclear Engineering and Radiological Sciences”. Educational Course in Michigan University, URL: . Sato, N.; Iwamoto, A. and Harada, K. (1983): “Preequilibrium Emission of Light Composite Particles in the Framework of the Exciton Model”. Physical Review C, V. 28, pp. 1527. Shang, Z. and Jun, Y. (1989): “The Formulation of UNIFY Code for the Calculation of Fast Neutron Data for Structural Materials”. Technical Report INDC(CPR)-014, IAEA, Vienna, Austria. Shirokov, Yu. M. and Yudin, N. P. (1982): “Nuclear Physics”. Mir Publisher. Moscow, USSR. Shultis, J. K. and Faw, R. E. (2002): “Fundamentals of Nuclear Science and Engineering”. Marcel Dekker, Inc. USA.

121

References Siciliano, E. R. (2004): “Medical Radioisotope Data Survey: 2002 Preliminary Results”. Pacific Northwest National Laboratory PNNL-14882, Springfield. Sierk, A. J. (1986): “Macroscopic Model of Rotating Nuclei”. Physical Review C, V. 33, pp. 2039. Singh, R. and Mukherjee, S. N. (1996): “Nuclear Reactions” NeAge International Limited, Publishers, India. Smith, F. A. (2000): “A Primer of Applied Radiation Physics”. World Scientific Publishing Co. Pte. Ltd. Singapore. Stake, M. and Mido, Y. (2003): “An Introduction to Nuclear Chemistry”. Discovery Publishing House, New Delhi, India. Stanley Humphries, Jr. (1986): “Principles of Charged Particles Acceleration”. John Wiley & Sons, Inc. New York, USA. Székely, G. (1985): “FGM - A Flexible Gamma-Spectrum Analysis Program for A small Computer”. Journal of Computer Physics Communications, V. 34, pp. 313. Szelecsényi, F.; Kovács, Z.; Tárkányi, F. and Tóth, Gy. (1991): “Production of 110In for PET Investigation Via 110Cd(3He,3n)110Sn→110In Reaction with Low Energy Cyclotron”. Journal of Labelled Compounds and Radiopharmaceuticals, V. 30, pp. 98. Tamura, T.; Udagawa, T. and Lenske, H. (1982): “Multistep Direct Reaction Analysis of Continuum Spectra in Reactions Induced by Light Ions”. Physical Review C, V. 26, pp. 379. Tárkányi, F.; Király, B.; Ditrói, F.; Takács, S.; Csikai, J.; Hermanne, A.; Uddin, M. S.; Hagiwara, M.; Baba, M.; Ido, T.; Shubin, Yu. N. and Kovalev, S. F. (2006): “Activation Cross Sections on Cadmium: Proton Induced Nuclear Reactions Up to 80 MeV”. Journal of Nuclear Instruments and Methods in Physics Research B, V. 245, pp. 379. Tárkányi, F.; Király, B.; Ditrói, F.; Takács, S.; Csikai, J.; Hermanne, A.; Uddin, M. S.; Hagiwara, M.; Baba, M.; Ido, T.; Shubin, Yu. N. and Kovalev, S. F. (2007): “Activation Cross Sections on

122

References Cadmium: Deuteron Induced Nuclear Reactions up to 40 MeV”. Journal of Nuclear Instruments and Methods in Physics Research B, V. 259, pp. 817. Tárkányi, F.; Szelecsényi, F.; Kopecký, P.; Molnár, T.; Andó, L.; Mikecz, P.; Tóth, Gy. and Rydl, A. (1994): “Cross Sections of Proton Induced Nuclear Reactions on Enriched 111Cd and 112Cd for the Production of 111In for Use in Nuclear Medicine”. Journal of Applied Radiation and Isotopes, V. 45, pp. 239. Tárkányi, F.; Takács, S.; Gul, K.; Hermanne, A.; Mustafa, M. G.; Nortier, M.; Obložinský, P.; Qaim, S. M.; Scholten, B.; Shubin, Yu. N. and Zhuang, Y. (2001): “Beam Monitor Reactions: Charged Particle Cross-Section Database for Medical Radioisotope Production”. TECDOC-1211, IAEA, Vienna. Tárkányi, F.; Takács, S.; Hermanne, A.; Van Den Winkel, P.; Van Der Zwart, R.; Skakun, Y.; Shubin, Yu. N. and Kovalev, S. F. (2005): “Investigation of the Production of the Therapeutic Radioisotope 114mIn through Proton and Deuteron Induced Nuclear Reactions on Cadmium”. Journal of Radiochimica Acta, V. 93, pp. 561. Thomas Wichert and Manfred Deicher (2001): “Studies of Semiconductors”. Nuclear Physics A, V. 693, pp. 327. Wernick, M. N. and Aarsvold, J. N. (2004): “Emission Tomography: The Fundamentals of PET and SPECT”. Elsevier Inc. China. Williamson, C. F.; Boujot, J. P. and Picard, J. (1966): “Tables of Range and Stopping Power of Chemical Elements for Charged Particles of Energy 0.5-500 MeV”. Saclay Report CEA-R 3042, France. Ziegler, J. F. (1980): “Handbook of Stopping Cross Sections for Energetic Ions in All Elements”. Pergamon Press, New York. USA.

123 Summary

حًج يقاسَت انُخائش انًعًهيت انخي عصهُا عهيٓا يع انُخائش انًعًهيت انخي حى انغصٕل عهيٓا يٍ انذساساث انسابقت باإلظافت اني يقاسَت انُخائش انعًهيت كهٓا بُخائش انغساباث انُظشيت. في انُٓايت حى دساست انُسبت بيٍ انًقاطع انًسخعشظت نبعط األَٕيت في عاالث اإلراسة ٔعذو اإلراسة ٔيُٓا حى عساب آنيت عذٔد انخفاعم رى اخيشا حى عساب اإلَخاس انخكايهي نبعط انُظائش راث انخطبيقاث انًًٓت.

XII Summary

الملخص العربي

في ْزِ انشسانت حًج دساست انخفاعالث انُٕٔيت انًسخغزت بانٓيهيٕو-3 عهي عُصش انكادييٕو في انغانت انطبيعيت باسخخذاو طشيقت انششائظ انًخشاصت. ٔقذ كخبج انشسانت في أسبعت فصٕل كًا يهي:

 انفصم األٔل: يشًم يُاقشت يبادئ انخفاعالث انُٕٔيت ٔعشكيت انخفاعالث ٔ آنياحٓا. كًا حًج يُاقشت طاقت انخٕقف نهضسيًاث انًشغَٕت ٔدساست انًقاطع انًسخعشظت نهخفاعالث انُٕٔيت ٔدٔال اإلراسِ. أيعا حًج دساست يبادئ عًم يطياف أشعت صايا ٔكفائخٓا. بعذ رنك حى عشض َخائش انذساساث انسابقت نهخفاعالث قيذ انذساست. ٔفي انُٓايت حى اسخعشاض األْذاف انعًهيت ٔانُظشيت يٍ ْزِ انذساست.

 انفصم انزاَي: ٔيشًم ششط يفصم نألصٓضة ٔانخقُياث انخضشيبيت انًسخخذيت ْٔي طشيقت حغعيش األْذاف باسخخذاو حقُيت انششائظ انًخشاصت ٔششط حفصيهي نًعضم انسيكهٕحشٌٔ طشاص MGC-20 ٔيكَٕاحّ. ٔحى ششط يطياف اشعت صايا فائق انذقت ٔكيفيت اسخخذايّ في عساب انُشاغ اإلشعاعي انًسخغذ ف األْذاف انًشععت بٕاسطت انسيكهٕحشٌٔ.

 انفصم انزانذ: ٔيخُأل ْزا انفصم ششط انغساباث انُظشيت نهًقاطع انًسخعشظت باسخخذاو انًُارس انُظشيت نهخفاعالث انُٕٔيت ٔقذ حًج يُاقشت رالرت ًَارس َظشيت نهخفاعالث انُٕٔيت ْٔي ALICE-IPPE, TALYS-1.2 and EMPIRE-03

 انفصم انشابع: ٔيغخٕي ْزا انفصم عهي عشض نهُخائش انخضاسب انًعًهيت ٔانغساباث انُظشيت ٔحغهيهٓا. حًج دساست دٔال اإلراسة نهخفاعالث انُٕٔيت انخانيت; natCd(3He,xn)117m,113g,111,110Sn, natCd(3He,x)117m,g,116m,115m,114m,113m,111g,110m,g,109g,108g,107gIn, natCd(3He,x)115g,111mCd

الملخص العربي

جاهعة عيي شوس كلية العلـــــــــــىم قسن الفيسيــــــــاء

التفاعالت الٌىوية الوستحثة بالجسيوات الخفيفة الوشحىًة علي بعض األًىية هتىسطة الىزى للتطبيقات العولية

زصبلة هقدهة هي

بهاء هحوذ علي هحوذ هحسٌة

للحصىل علي دزجة الوبجضتيس في العلىم )الفيزيبء النىوية(

الوشسفىى التىقيع

ا.د. سوير يىشع الخويسي

ا.د. أساهة صذيق عبذ الغفار

د. هجاهذ ابراهين األبيض

جاهعة عيي شوس كلية العلـــــــــــىم قسن الفيسيــــــــاء التفاعالت الٌىوية الوستحثة بالجسيوات الخفيفة الوشحىًة علي بعض األًىية هتىسطة الىزى للتطبيقات العولية

زصبلة هقدهة هي

بهاء هحوذ علي هحوذ هحسٌة

للحصىل علي دزجة الوبجضتيس في العلىم )الفيزيبء النىوية(

الوشرفىى

ا.د. سوير يىشع الخويسي اصتبذ الفيزيبء النىوية قضن الفيزيـــــــــــــبء كلية العلـــــــــــــــىم جبهعة عيي شوـــــش

ا.د. أساهة صذيق عبذ الغفار اصتبذ الفيزيبء النىوية والجضيوية قضن الفيزيــــــــــــــــبء هسكز البحىث النىوية هيئة الطبقة الرزيــــــة

د. هجاهذ ابراهين األبيض هدزس الفيزيبء النىوية قضن الفيزيــــــــــــــــبء هسكز البحىث النىوية هيئة الطبقة الرزيــــــة

جاهعة عيي شوس كلية العلـــــــــــىم قسن الفيسيــــــــاء

التفاعالت الٌىوية الوستحثة بالجسيوات الخفيفة الوشحىًة علي بعض األًىية هتىسطة الىزى للتطبيقات العولية

زصبلة هقدهة هي

بهبء هحود علي هحود هحضنة

بكبلىزيىس فيزيبء-٤٠٠٢

للحصىل علي دزجة الوبجضتيس في العلىم )الفيزيبء النىوية(

الي

قضن الفيزيبء- كلية العلىم جبهعة عيي شوش

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