DOCSLIB.ORG

NUCLIDES FAR OFF the STABILITY LINE and SUPER-HEAVY NUCLEI in HEAVY-ION NUCLEAR REACTIONS Marc Lefort

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
NUCLIDES FAR OFF the STABILITY LINE and SUPER-HEAVY NUCLEI in HEAVY-ION NUCLEAR REACTIONS Marc Lefort NUCLIDES FAR OFF THE STABILITY LINE AND SUPER-HEAVY NUCLEI IN HEAVY-ION NUCLEAR REACTIONS Marc Lefort To cite this version: Marc Lefort. NUCLIDES FAR OFF THE STABILITY LINE AND SUPER-HEAVY NUCLEI IN HEAVY-ION NUCLEAR REACTIONS. Journal de Physique Colloques, 1972, 33 (C5), pp.C5-73-C5- 102. 10.1051/jphyscol:1972507. jpa-00215109 HAL Id: jpa-00215109 https://hal.archives-ouvertes.fr/jpa-00215109 Submitted on 1 Jan 1972 HAL is a multi-disciplinary open access L’archive ouverte pluridisciplinaire HAL, est archive for the deposit and dissemination of sci- destinée au dépôt et à la diffusion de documents entific research documents, whether they are pub- scientifiques de niveau recherche, publiés ou non, lished or not. The documents may come from émanant des établissements d’enseignement et de teaching and research institutions in France or recherche français ou étrangers, des laboratoires abroad, or from public or private research centers. publics ou privés. JOURNAL RE PHYSIQUE CoLIoque C5, supplement au no 8-9, Tome 33, Aoiit-Septembre 1972, page C5-73 NUCLIDES FAR OFF THE STABILITY LINE AND SUPER-HEAVY NUCLEI IN HEAW-ION NUCLEAR REACTIONS by Marc Lefort Chimie Nucleaire-Institut de Physique Nucleaire-ORSAY, France Abstract A review is given on the new species which attempts already made for the synthesis of super- have been produced in the recent years by heavy ion heavy elements. A discussion is presented on the reactions, mainly 12C, 160, ''0, 22~eand 20~eions. following problems : reaction thresholds and The first section is devoted to the formation of coulomb barriers for heavily charged projectiles, neutron rich exotic light nuclei and to the mecha- complete fusion cross section as compared to the nism of multinuclear transfer reactions responsible total cross section, main decay channels for exci- for this formation. In the second section dealing ted compound nuclei in the region Z = 118, on medium atomic numbers a brief account is made on N = 184-190, fusion-fission reactions and the the discovery of proton radioactivity and some com- possibility of production of S.H. elements as ments are made on the difficulties encountered for fission fragments, grazing reactions and exchange producing very neutron deficient isotopes 1i ke ' !:~n. of big apsregates . The study of the region of neutron deficiency for rare earth is one of the most fruitful field Resume for heavy ion reactions. More than fifty new iso- Noyaux loin de la Stabilite et Noyaux topes have been found. A discussion is made on the Super-lourds dans 1es Reactions Nucltiaires par possibility for going further into the neutron Ions tourds. deficiency open by the use of Ar, Kr and heavier ions. It is shown that there is no advantage to Cet expose consiste en une revue sur 1es bombard targets with ions heavier than "'Ca or '%Ni, nomt.reux nouveaux noyaux produits depuis quelques Section 4 is devoted to heavy nuclei in the annees par les reactions par ions lourds, et en une discussion des possibilites ouvertes par les region of the neutron shell N = 126. Fission compe- tition is discussed as well as the limitation of the faisceaux d'ions plus lourds 'OAr, "Ca, 84Kr, compound nucleus cross section due to high angular '36Xe etc .. Les tentatives de synthese de noyaux superlourds sont momentum effects. Results are presented on the rota- decrites brievement. ting liquid drop and the very strong diminution of Dans le premier paragraphe, on insiste sur- fission barriers due to rotational energy. A brief tout sur les noyaux riches en neutrons depuis le review is made of the new decay families discovered bore jusqu'a l'argon, produits grtce ii des trans- by Hyde et a?. t631 for light thorium and protacti- ferts d'un grand nombre de neutrons depuis des nium isotopes, These results are one of the great cibles lourdes vers le projectile. I1 est possible success of heavy-ion induced reactions. d'approcher la limite d'existence des noyaux oil Section 5 reminds that all isotopes of ele- l'energie de liaison du neutron devient nulle. Le ments beyond Z = 101 have been produced by heavy- second paragraphe traite des noyaux moyens pour les- ion reactions, in spite of the great fission compe- quels les seuls essais ayant donne quelques resul- tition. tats ont pennis de trouver que les tellures tres legers (107, 108) etaient emetteurs alpha et de The 1ast section describes the various d@couvrir la radioactivite par proton sur le Article published online by EDP Sciences and available at http://dx.doi.org/10.1051/jphyscol:1972507 cobalt 53. Les possibilitGs de formation de noyaux L'existence d'une sous couche 1 164 neutrons laisse tres deficients en neutrons tels '!:~n ou t:Zr quelques espoirs de produire des isotopes riches en sont etudiees. neutrons 1 durges de vie encore acceptablespour Z = 105 et Z = 106. Des calculs sont presentes qui montrent que meme si des noyaux compos@s relativement legers Enfin, la derniere partie est consacree aux peuvent &re produits , leur desexci tation a 1ieu noyaux Superlourds. Apres quelques mots sur la si- essentiellement par emission de particules chargees tuation tres optimiste des previsions theoriques et qu'il est tres improbable d'atteindre la zone concernant la stabilite des noyaux 1 l'etat fonda- N = Z. mental autour de Z = 114 et N = 184, les problemes poses par les chances d'atteindre ces noyaux par La troisieme partie du memoire Studie le les reactions nucleaires connues sont discutes domaine des terres rares dans lequel les reactions . 1") La barriere de potentiel pour l'approche d'un par ions lourds ont fait decouvrir plus de 50 nou- projectile lourd a et@mesuree et se revele plzs veaux isotopes emetteurs a partiellement pour la elevee que pour les ions plus 16gers fro = 1,32 au ~lu~art.. La couche N = 82 est ainsi a~~rochee, , et 1ieu de ro = 1,45-1,50). on peut raisonnablement es~ererau moven des ions 2") La fusion complete conduisant 1 un noyau compo- "Ca ou ' OAr produire des isotopes encore plus se plus lourd que l'uranium semble tres difficife legers dans la region de noyaux tres d&formGs sinon impossible pour des projectiles de Z superieur Z = 58-70,N = 70-82. L'utilisation d'ions plus 1 20. Ceci apparaTt travers certains resultats lourds que ::~ine paraft presenter aucun evantage. a oreliminaires obtenus avec les ions Kr et se trouve Les noyaux lourds de N plus ou moins eloigne justifie par llanalyse de ltinfluence de de N = 126 sont ensuite etudies. Dans cette region, de rotation lEnerqie- NYrast~) et des barrieres de la competition de la fission devient importante et fission pour une goutte liquide en rotation. limite les sections efficaces. De plus, l'energie 3O) La desexcitation d'eventuels noyaux compos@s de rotation elevee introduite par les grands mo- devrait avoir lieu par emission alpha et permettre ments angulaires projectiles lourds conduit a d'atteindre les noyaux superlourds 1 vie longue. abaisser la barriere de fission et 1 rendre impos- Les remarquables donnees de ~ix~l~l)sur cette sible la formation de noyau compose pour les ondes question sont cornentees et quelques reactions partielles de l'h eleve. Oes valeurs de aCF/aR , favorables indiquees. On mentionne les resultats rapport de la section efficace de fusion complete obtenus jusqu'ici pour les tentatives effectuees 1 1 la section totale de reaction sont calculees et Orsay (*'~r+~~~Th)et (84Kr+208Pb), resultats nega comparees 1 des resultats experimentaux obtenus tifs malgre la mise en oeuvre de moyens de detec- avec les ions Ar et Kr. Enfin, dans cette region tion elabores pour les masses autour de A = 300. des elements Rn a Pa, le plus grand succes des Le choix de projectiles 82Se, 76Ge ou ?'Ga seraft reactions par ions lourds C, N, 0, Ne a et@la peut-&re meilleur. decouverte de nombreux isotopes legers. De nouvel- Enfin, d'autres possibilites que le passage les familles a d~croissancesen chaine ont ete par noyau compose sont indiquees. Les experiences mises en evidence par Hyde et ses collaborateurs avec le faisceau de xenon faites Dubna sont men- 1631, 1 partir d'isotopes legers de thorium et de 5 protactinium. tionnees come approche de la methode dite "fusion- fission" qui consiste 1 produire un enorme noyau Dans la 5e partie, on rappelle que tous les de fusion A = 400 et esperer que parmi les frag- isotopes des transmendeleviens Z > 101 ont ete mis ments de fission de ce noyau, des elements super- en evidence grace aux reactions induites sur des lourds soient crees. Les transferts de gros agrP- cibles de 238U, 239P~924ZP~, 248Cms *"Cf par gats sont une autre possibilit@pour laquelle le des ions de bore, carbone, oxygPne on neon, et ceci manque d ' information precise empPche de faire des malgre de faibles sections efficaces inferieures 1 previsions. 1 microbarn en raison de l'importance de la fission. SUPER-HEAVY NUCLEI .. C5-75 INTRODUCTION appears to be a limit to the process of synthesis by neutron fluxes of very high density. The first nuclear reactions induced by heavy ions were observed more than twenty years Then, the only possibility is to take ago. In 1949, carbon ions were accelerated in the the heaviest available targets, curi urn, berkelium, 152cm Berkeley cyclotron and a low intensity beam californium and einsteini um, and bombard them with was used by Hamil ton et a1 [I).These authors heavy ions. Pionners in this challenge were the showed that 34~1was produced from aluminium tar- Nobel Institute in Stockholm where Atterling et a1 gets and 205~tfrom gold.
Load more

Recommended publications
  • An Octad for Darmstadtium and Excitement for Copernicium
    SYNOPSIS An Octad for Darmstadtium and Excitement for Copernicium The discovery that copernicium can decay into a new isotope of darmstadtium and the observation of a previously unseen excited state of copernicium provide clues to the location of the “island of stability.” By Katherine Wright holy grail of nuclear physics is to understand the stability uncover its position. of the periodic table’s heaviest elements. The problem Ais, these elements only exist in the lab and are hard to The team made their discoveries while studying the decay of make. In an experiment at the GSI Helmholtz Center for Heavy isotopes of flerovium, which they created by hitting a plutonium Ion Research in Germany, researchers have now observed a target with calcium ions. In their experiments, flerovium-288 previously unseen isotope of the heavy element darmstadtium (Z = 114, N = 174) decayed first into copernicium-284 and measured the decay of an excited state of an isotope of (Z = 112, N = 172) and then into darmstadtium-280 (Z = 110, another heavy element, copernicium [1]. The results could N = 170), a previously unseen isotope. They also measured an provide “anchor points” for theories that predict the stability of excited state of copernicium-282, another isotope of these heavy elements, says Anton Såmark-Roth, of Lund copernicium. Copernicium-282 is interesting because it University in Sweden, who helped conduct the experiments. contains an even number of protons and neutrons, and researchers had not previously measured an excited state of a A nuclide’s stability depends on how many protons (Z) and superheavy even-even nucleus, Såmark-Roth says.
    [Show full text]
  • Spallation Neutron Sources for Science and Technology
    Proceedings of the 8th Conference on Nuclear and Particle Physics, 20-24 Nov. 2011, Hurghada, Egypt SPALLATION NEUTRON SOURCES FOR SCIENCE AND TECHNOLOGY M.N.H. Comsan Nuclear Research Center, Atomic Energy Authority, Egypt Spallation Neutron Facilities Increasing interest has been noticed in spallation neutron sources (SNS) during the past 20 years. The system includes high current proton accelerator in the GeV region and spallation heavy metal target in the Hg-Bi region. Among high flux currently operating SNSs are: ISIS in UK (1985), SINQ in Switzerland (1996), JSNS in Japan (2008), and SNS in USA (2010). Under construction is the European spallation source (ESS) in Sweden (to be operational in 2020). The intense neutron beams provided by SNSs have the advantage of being of non-reactor origin, are of continuous (SINQ) or pulsed nature. Combined with state-of-the-art neutron instrumentation, they have a diverse potential for both scientific research and diverse applications. Why Neutrons? Neutrons have wavelengths comparable to interatomic spacings (1-5 Å) Neutrons have energies comparable to structural and magnetic excitations (1-100 meV) Neutrons are deeply penetrating (bulk samples can be studied) Neutrons are scattered with a strength that varies from element to element (and isotope to isotope) Neutrons have a magnetic moment (study of magnetic materials) Neutrons interact only weakly with matter (theory is easy) Neutron scattering is therefore an ideal probe of magnetic and atomic structures and excitations Neutron Producing Reactions
    [Show full text]
  • Production and Properties Towards the Island of Stability
    This is an electronic reprint of the original article. This reprint may differ from the original in pagination and typographic detail. Author(s): Leino, Matti Title: Production and properties towards the island of stability Year: 2016 Version: Please cite the original version: Leino, M. (2016). Production and properties towards the island of stability. In D. Rudolph (Ed.), Nobel Symposium NS 160 - Chemistry and Physics of Heavy and Superheavy Elements (Article 01002). EDP Sciences. EPJ Web of Conferences, 131. https://doi.org/10.1051/epjconf/201613101002 All material supplied via JYX is protected by copyright and other intellectual property rights, and duplication or sale of all or part of any of the repository collections is not permitted, except that material may be duplicated by you for your research use or educational purposes in electronic or print form. You must obtain permission for any other use. Electronic or print copies may not be offered, whether for sale or otherwise to anyone who is not an authorised user. EPJ Web of Conferences 131, 01002 (2016) DOI: 10.1051/epjconf/201613101002 Nobel Symposium NS160 – Chemistry and Physics of Heavy and Superheavy Elements Production and properties towards the island of stability Matti Leino Department of Physics, University of Jyväskylä, PO Box 35, 40014 University of Jyväskylä, Finland Abstract. The structure of the nuclei of the heaviest elements is discussed with emphasis on single-particle properties as determined by decay and in- beam spectroscopy. The basic features of production of these nuclei using fusion evaporation reactions will also be discussed. 1. Introduction In this short review, some examples of nuclear structure physics and experimental methods relevant for the study of the heaviest elements will be presented.
    [Show full text]
  • Fusion and Spallation Irradiation Conditions Steven J
    Fusion and Spallation Irradiation Conditions Steven J. Zinkle Metals and Ceramics Division Oak Ridge National Laboratory, Oak Ridge, TN International Workshop on Advanced Computational Science: Application to Fusion and Generation-IV Fission Reactors Washington DC, March 31-April 2, 2004 Comparison of fission and fusion (ITER) neutron spectra Stoller & Greenwood, JNM 271-272 (1999) 57 • Main difference between fission and DT fusion neutron spectra is the presence of significant flux above ~4 MeV for fusion –High energy neutrons typically cause enhanced production of numerous transmutation products including H and He –The Primary Knock-on Atom (PKA) spectra are similar for fission and fusion at low energies; fusion contains significant high-energy PKAs (>100 keV) Displacement Damage Mechanisms are being investigated with Molecular Dynamics Simulations Damage efficiency saturates when subcascade formation occurs Avg. Avg. fission fusion Molecular dynamics modeling of displacement cascades up to 50 keV PKA 200 keV and low-dose experimental tests (microstructure, tensile (ave. fusion) properties, etc.) indicates that defect production from fusion and fission neutron collisions are similar 10 keV PKA => Defect source term is similar for fission and fusion conditions (ave. fission) Peak damage state in iron cascades at 100K 5 nm A critical unanswered question is the effect of higher transmutant H and He production in the fusion spectrum Radiation Damage can Produce Large Changes in Structural Materials • Radiation hardening and embrittlement
    [Show full text]
  • Synthesis of Neutron-Rich Transuranic Nuclei in Fissile Spallation Targets
    Synthesis of neutron-rich transuranic nuclei in fissile spallation targets Igor Mishustina,b, Yury Malyshkina,c, Igor Pshenichnova,c, Walter Greinera aFrankfurt Institute for Advanced Studies, J.-W. Goethe University, 60438 Frankfurt am Main, Germany b“Kurchatov Institute”, National Research Center, 123182 Moscow, Russia cInstitute for Nuclear Research, Russian Academy of Science, 117312 Moscow, Russia Abstract A possibility of synthesizing neutron-reach super-heavy elements in spal- lation targets of Accelerator Driven Systems (ADS) is considered. A dedi- cated software called Nuclide Composition Dynamics (NuCoD) was developed to model the evolution of isotope composition in the targets during a long-time irradiation by intense proton and deuteron beams. Simulation results show that transuranic elements up to 249Bk can be produced in multiple neutron capture reactions in macroscopic quantities. However, the neutron flux achievable in a spallation target is still insufficient to overcome the so-called fermium gap. Fur- ther optimization of the target design, in particular, by including moderating material and covering it by a reflector will turn ADS into an alternative source of transuranic elements in addition to nuclear fission reactors. 1. Introduction Neutrons propagating in a medium induce different types of nuclear reactions depending on their energy. Apart of the elastic scattering, the main reaction types for low-energy neutrons are fission and neutron capture, which dominate, respectively, at higher and lower energies with the boarder
    [Show full text]
  • Status of the Project and Physics of the Spallation Target
    PHYSOR 2004 -The Physics of Fuel Cycles and Advanced Nuclear Systems: Global Developments Chicago, Illinois, April 25-29, 2004, on CD-ROM, American Nuclear Society, Lagrange Park, IL. (2004) The TRADE Experiment: Status of the Project and Physics of the Spallation Target C. Rubbia1, P. Agostini1, M. Carta1, S. Monti1, M. Palomba1, F. Pisacane1, C. Krakowiak2, M. Salvatores2, Y. Kadi*3, A. Herrera-Martinez3, L. Maciocco4 1ENEA, Lungotevere Thaon di Revel, 00196 Rome, ITALY 2CEA, CEN-Cadarache, 13108 Saint-Paul-Lez-Durance, FRANCE 3CERN, 1211 Geneva 23, SWITZERLAND 4AAA, 01630 Saint-Genis-Pouilly, FRANCE The neutronic characteristics of the target-core system of the TRADE facility have been established and optimized for a reference proton energy of 140 MeV. Similar simulations have been repeated for two successive upgrades of the proton energy, 200 and 300 MeV, corresponding to different performances and design requirements and different characteristics of the proposed cyclotron and, as a consequence, of the proton beam. An extensive comparison of the main physical parameters has been also carried out, in order to evaluate advantages and disadvantages of different proton beam energies in the design of the spallation target and to allow the optimal engineering design of the whole TRADE facility. KEYWORDS: TRADE facility, ADS, Spallation target physics, Experimentation, External neutron sources, intermediate proton energy. 1. Introduction The TRADE “TRiga Accelerator Driven Experiment”, to be performed in the existing TRIGA reactor of the ENEA Casaccia Centre, has been proposed as a major project in the way for validating the ADS concept. Actually, TRADE will be the first experiment in which the three main components of an ADS – the accelerator, the spallation target and the sub- critical blanket – will be coupled at a power level sufficient to appreciate feedback reactivity effects.
    [Show full text]
  • Spallation and Neutron-Capture Produced Cosmogenic Nuclides in Aubrites
    70th Annual Meteoritical Society Meeting (2007) 5054.pdf SPALLATION AND NEUTRON-CAPTURE PRODUCED COSMOGENIC NUCLIDES IN AUBRITES. J. Masarik1, K. Nishiizumi2 and K. C. Welten2, 1Department of Nuclear Physics, Comenius University Bratislava, Slovakia, E-mail: ma- [email protected], 2Space Sciences Laboratory, University of California, Berkeley, CA 94720, USA, Introduction: A purely physical model for the simulation of cosmic-ray-particle interactions with matter was used to investi- gate the production rates of cosmogenic nuclides in aubrites with radii ranging from 5 cm to 120 cm. Production rates of spal- logenic and neutron-capture produced nuclides were investigated and compared with measured cosmogenic nuclide concentrations to constrain the complex exposure histories of aubrites. Calculational Model: The numerical simulation of interac- tions of primary and secondary cosmic-ray particles was done with the LAHET Code System (LCS) [1] which uses MCNP [2] for transport of low energy neutrons. The investigated objects were spheres with various radii that were divided into spherical layers. We used the spectrum of the galactic-cosmic-ray particles corresponding to solar modulation parameter Φ = 550 MeV and a flux of 4.8 protons/s·cm2. The statistical errors of the LCS calcu- lated fluxes were 3–5%. The production rates of nuclides were calculated by integrating over energy the product of these fluxes and cross sections for the nuclear reactions making the investi- gated nuclide. For cross sections of spallogenic products, we relied on the values evaluated by us and tested by earlier calcula- tions [e.g., 3]. Previous calculations of the 53Mn production rate in aubrites showed good agreement with measured 53Mn concen- trations in the Norton County aubrite [4].
    [Show full text]
  • Pulsed Spallation Neutron Sources
    (LoMr^** U-J / •*> =* —%3 f& APR 1 7 1938 OSTI PULSED SPALLATION NEUTRON SOURCES John M. Carpenter Intense Pulsed Neutron Source Division Argonne National Laboratory This paper reviews the early history of pulsed spallation neutron source development at Argonne and provides an overview of existing sources world wide. A number of proposals for machines more powerful than currently exist are under development, which are briefly described. I review the status of the Intense Pulsed Neutron Source, its instrumentation, and its user program, and provide a few examples of applications in fundamental condensed matter physics, materials science and technology. HISTORY OF PULSED SOURCE DEVELOPMENTS AT ARGONNE This is a day for remembering, reflecting and projecting into the future. Think back to the year 1968,26 years ago. Please don't fix upon the gathering war half a world away, the * burnings in our cities, or the riots in our own Grant Park; these were dark rumblings of political change that even now have not played out. Think instead of the scientific scene. ZGS had already been operating for five years and improvements were afoot. New, bigger machines were being designed and built around the world for high energy physics research. Several high flux research reactors were under design, construction or commissioning: HFBR (Brookhaven), HFIR (Oak Ridge), HFR (ILL Grenoble), A^R2 (Argonne), British HFR. Argonne had an already long-established tradition in neutron scattering based on its smaller research reactors, beginning with Enrico Fermi and Walter Zinn at CP-3, and continuing at the 5-MW CP-5. In January of 1968, as a young and dewy professor of Nuclear Engineering at the University of Michigan, where I had built some instruments for neutron scattering research at the 2-MW Ford Reactor, I was invited to serve in an instrument design group, led by Don Connor of the SSS division, that was supposed eventually to provide instruments for A^R2.
    [Show full text]
  • Nuclear Magic Numbers: New Features Far from Stability
    Nuclear magic numbers: new features far from stability O. Sorlin1, M.-G. Porquet2 1Grand Acc´el´erateur National d’Ions Lours (GANIL), CEA/DSM - CNRS/IN2P3, B.P. 55027, F-14076 Caen Cedex 5, France 2Centre de Spectrom´etrie Nucl´eaire et de Spectrom´etrie de Masse (CSNSM), CNRS/IN2P3 - Universit´eParis-Sud, Bˆat 104-108, F-91405 Orsay, France May 19, 2008 Abstract The main purpose of the present manuscript is to review the structural evolution along the isotonic and isotopic chains around the ”traditional” magic numbers 8, 20, 28, 50, 82 and 126. The exotic regions of the chart of nuclides have been explored during the three last decades. Then the postulate of permanent magic numbers was definitely abandoned and the reason for these structural mutations has been in turn searched for. General trends in the evolution of shell closures are discussed using complementary experimental information, such as the binding energies of the orbits bounding the shell gaps, the trends of the first collective states of the even-even semi-magic nuclei, and the behavior of certain single-nucleon states. Each section is devoted to a particular magic number. It describes the underlying physics of the shell evolution which is not yet fully understood and indicates future experimental and theoretical challenges. The nuclear mean field embodies various facets of the Nucleon- Nucleon interaction, among which the spin-orbit and tensor terms play decisive roles in the arXiv:0805.2561v1 [nucl-ex] 16 May 2008 shell evolutions. The present review intends to provide experimental constraints to be used for the refinement of theoretical models aiming at a good description of the existing atomic nuclei and at more accurate predictions of hitherto unreachable systems.
    [Show full text]
  • 1 Spallation Neutron Source and Other High Intensity
    SPALLATION NEUTRON SOURCE AND OTHER HIGH INTENSITY PROTON SOURCES* WEIREN CHOU Fermi National Accelerator Laboratory P.O. Box 500 Batavia, IL 60510, USA E-mail: [email protected] This lecture is an introduction to the design of a spallation neutron source and other high intensity proton sources. It discusses two different approaches: linac-based and synchrotron-based. The requirements and design concepts of each approach are presented. The advantages and disadvantages are compared. A brief review of existing machines and those under construction and proposed is also given. An R&D program is included in an appendix. 1. Introduction 1.1. What is a Spallation Neutron Source? A spallation neutron source is an accelerator-based facility that produces pulsed neutron beams by bombarding a target with intense proton beams. Intense neutrons can also be obtained from nuclear reactors. However, the international nuclear non-proliferation treaty prohibits civilian use of highly enriched uranium U235. It is a showstopper of any high efficiency reactor-based new neutron sources, which would require the use of 93% U235. (This explains why the original proposal of a reactor-based Advanced Neutron Source at the Oak Ridge National Laboratory in the U.S. was rejected. It was replaced by the accelerator-based Spallation Neutron Source, or SNS, project.) A reactor-based neutron source produces steady higher flux neutron beams, whereas an accelerator-based one produces pulsed lower flux neutron beams. So the trade-off is high flux vs. time structure of the neutron beams. This course will teach accelerator-based neutron sources. An accelerator-based neutron source consists of five parts: 1) Accelerators 2) Targets 3) Beam lines * This work is supported by the Universities Research Association, Inc., under contract No.
    [Show full text]
  • Proton Induced Spallation Reactions in the Energy Range
    JAGIELLONIAN UNIVERSITY INSTITUTE OF PHYSICS Proton induced spallation reactions in the energy range 0.1 - 10 GeV Anna Kowalczyk arXiv:0801.0700v1 [nucl-th] 4 Jan 2008 A doctoral dissertation prepared at the Institute of Nuclear Physics of the Jagiellonian University, submitted to the Faculty of Physics, Astronomy and Applied Computer Science at the Jagiellonian University, conferred by Dr hab. Zbigniew Rudy Cracow 2007 Contents 1 Introduction 3 2 Present knowledge of the reaction dynamics - basic theoret- ical models 9 2.1 IntranuclearCascademodel . 10 2.2 Quantum Molecular Dynamics model . 11 2.3 Percolationmodel. .. .. 15 3 Specific models for fast stage of proton-nucleus collision 19 3.1 Transportequation . 20 3.2 Boltzmann-Uehling-Uhlenbeck model . 23 3.3 HadronStringDynamicsmodel . 25 3.3.1 Crosssections .. .. 26 3.3.2 StringModel ....................... 28 3.4 Further development of the model . 31 3.5 Stopping time criteria for the first stage model calculations . 32 4 Bulk properties of the first stage of proton induced reactions 39 5 Properties of residual nuclei after the first stage of proton - nucleus reactions 46 5.1 Parametrization. .. .. 66 6 Pion spectra 72 7 Statistical emission of particles in the second stage of proton - nucleus collisions 89 7.1 Evaporationmodel-PACE2 . 91 7.2 GeneralizedEvaporationModel . 92 1 2 8 Bulk models predictions for the proton induced nuclear re- actions 99 8.1 Illustration of energy balance of the reaction . .. 99 8.2 Participation of fission processes in spallation reaction. .100 9 Comparison of results of the HSD plus evaporation model calculations with experimental data 106 9.1 Neutronspectra.
    [Show full text]
  • Spallation Neutron Sources*
    Proceedings of the 1994 International Linac Conference, Tsukuba, Japan SPALLATION NEUTRON SOURCES* H. Klein Institut fUr Angewandte Physik der J. W. Gocthe-UniversiUil D-60054 Frankfurt am Main, FRG Abstract Principles of Neutron Spallation Sources At present mainly two types of neutron sources arc in usc If high energy (e.g. 800 MeV) protons impinge on tlJe for neutron scattering research, the steady state source based on target, tlley do not interact with the nucleus as a whole, but - fission reactors using highly enriched U235 fuel and the acce­ due to tileir short de Broglie wavelength - with the individual lerator based pulsed source, where the neutrons arc produced by nucleons, creating an intranuclear cascade inside tile nucleus; spallation of a nonfissile target. Several high intensi ty some high energy (secondary) neutrons and protons escape spallation sources arc under consideration nowadays, and these from tlle nucleus producing similar ca<;cades in neighbouring proposals as well as the existing machines will be reviewed. nuclei. The nucleus is left in a highly excited state and relaxes Besides the general layout of the facilities the problems of the mainly by evaporating low energy neutrons. The high energy high currentlinac part will be shortly discussed. neutrons are of no use, but the others, produced eitlJer by evaporation or directly by the incident protons, can be slowed down to thennal (or - for time of flight experiments - epi­ Introduction tlJennaI) velocities by optimized moderators. This optimi­ h"ltion is not possible Witll reactors, since a special moderator Neutrons are very well suited to study the microscopic layout is needed to sustain the chain-reaction.
    [Show full text]