THE PHOTODISINTEGRATION OF HELIUM-3 AT PHOTON ENERGIES OF 8.06 AND 9.17 MEV JACK ROBERT MACDONALD B.A.Sc•, The University of British Columbia, 1960 A THESIS SUBMITTED IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE DEGREE OF DOCTOR OF PHILOSOPHY in the Department of PHYSICS We accept this thesis as conforming to the required standard THE UNIVERSITY OF BRITISH COLUMBIA September 1964 In presenting this thesis in partial fulfilment of the requirements for an advanced degree at the University of British Columbia, I agree that the Library shall make it freely available for reference and study, I further agree that per• mission for extensive copying of this thesis for scholarly purposes may be granted by the Head of my Department or by his representatives. It is understood that,copying or publi• cation of this thesis for financial gain shall not be allowed without my written permission.-, Department of The University of British Columbia, Vancouver 8f Canada Date OCT^g^ ~7 , (^4 The University of British Columbia FACULTY OF GRADUATE STUDIES PROGRAMME OF THE FINAL ORAL EXAMINATION FOB, THE DEGREE OF DOCTOR OF PHILOSOPHY of JACK ROBERT MACDONALD B„A„Sccj The University of British Columbia* 1960 TUESDAY, OCTOBER 6, 1964, AT 3;-00 P.M. ROOM 12, HEBB BUILDING, (PHYSICS) COMMITTEE IN CHARGE Chairman; I. McT. Cowan W. Mo Armstrong D,„L..Livesey K. L» Erdman Jo Mo McMillan C. Froese. J. Bo Warren External Examiner: Leon Katz Department of Physics University of Saskatchewan THE PHOTODISINTEGBATION OF HELIUM-3 AT PHOTON ENERGIES OF 8.06 AM) 9,17 MEV. ABSTRACT The cross section for the photodisintegration of helium-3 has been measured at. gamma ray energies of 8,06 and 9.17 mev. The He3 (<JN,p)D reaction cross section at 8,06 and 9.17 mev was found t.o be 0,493 t 0.066 and 0,723 t 0,087 millibarns respectively. The He3 ,n)2p reaction cross section at 9,17 mev was found to be 0.25 i 0,13 millibarns. These results are compared with other experimental work on the photodisintegration of helium-3 and tritium. The photodisintegration reaction was observed in a cylindrical gridded ionization chamber using a helium- 3^ methane, and argon gas mixture. The, C^3(ps y )_t\jl4 reactions at proton bombarding energies of 0,554 and 1.75 mev were used as the source, of gamma rays of well defined energy. The preparation of carbon-13 targets is discussed in detail. Theoretical calculations on the photodisintegration of mass 3 nuclei are summarized, Photodisintegration and electron scattering measurements are compared as, methods of determining the nature of the ground state wave function of the mass 3 system. GRADUATE STUDIES Field of Study: Physics Electromagnetic Theory G.M, Volkoff Waves .J.G, Savage Nuclear Physics J.B. Warren Elementary Quantum. Mechanics W, Opechowski Nuclear Reactions BtL, White Solid State Physics R, Barrie Special Relativity Theory W, Opechowski Introduction to Low Temperature Physics D.V, Osborne Group Theory Methods~ W. Opechowski Theoretical Nuclear Physics P,D, Kunz Advanced Quantum Mechanics P, Rastall Related Studies: Numerical Analys is T.E,. Hull Electronic Instrumentation F.K, Bowers PUBLICATIONS Gas Flow Regulator for an rf Ion Source, Rev. Sci. Inst. 33, 1111 (1962) Removal of Tritium from Helium-3, Rev. Sci. Inst. 34, 1280 (1963) Photodisintegration of Helium-3, Bull. Amer. Phys,, Soc. 8, 124 (1963) Photodisintegration of Helium-*3 near the threshold, Phys. Rev. 132, 1691 (1963) Simple Gas Circulation Pump, Rev. Sci. Inst. 35, 241 (1964) Simple Electron Bombardment Apparatus for Evaporating Boron, Rev. Sci. Inst. 35, 122 (1964) -i- ABSTRACT The cross section for the photodisintegration of helium-3 has been measured at gamma ray energies of 8.06 and 9.17 mev. The He (£,p)D reaction cross section at 8.06 and 9.17 mev was found to be 0.493 ± 0.066 and 0.723 ± 0.087 millibarns respectively. The He (tf,n)2p reaction cross section at 9.17 mev was found to be 0.25 ± 0.13 millibarns. These results are compared with other experimental work on the photodisintegration of helium-3 and tritium. The photodisintegration reaction was observed in a cylindrical gridded ionization chamber using a helium-3, methane, and argon gas mixture. The C13(p,^)N14 reactions at proton bombarding energies of 0.554 and 1.75 mev were used as the source of gamma rays of well defined energy. The preparation of carbon-13 targets is discussed in detail. Theoretical calculations on the photodisintegration of mass 3 nuclei are summarized. Photodisintegration and electron scattering measurements are compared as methods of determining the nature of the ground state wave function of the mass 3 system. -ii- TABLE OF CONTENTS Page Chapter I - INTRODUCTION 1 Chapter II - THEORETICAL ESTIMATES OF THE CROSS SECTION FOR THE PHOTODISINTEGRATION OF HELIUM-3 ... 4 A. Reaction Kinematics 4 B. Theoretical Estimates of the Cross Section 5 Chapter III - PHOTODISINTEGRATION OF 3-BODY NUCLEI- EXPERIMENTAL RESULTS 10 Chapter IY - APPARATUS AND EXPERIMENTAL ARRANGEMENT FOR THE PHOTODISINTEGRATION MEASUREMENT 17 A. Introduction 17 B. Cylindrical Gridded Ionization Chamber 17 1. Chamber Operation 17 2. Chamber Construction 18 3. Gas Mixtures 20 C. Energy Calibration of the Chamber 23 D. Chamber Background 27 E. Pulse Amplification and Analysis 29 F. Gramma Flux Measurement 30 G. Experimental Arrangement 31 Chapter V - PHOTODISINTEGRATION RESULTS AND ESTIMATION OF THE CROSS SECTION AT 8.06 AND 9.17 MEV.. 33 A. Spectrum at 8.06 mev 33 B. Spectrum at 9.17 mev - 2-body Breakup 33 C. Spectrum at 9.17 mev - 3-body Breakup 34 D. Analysis of the 2-body Data 35 E. Cross Section Calculation for the Reaction He3()r,p)D 36 -iii- Page Chapter Y (cont) F. Errors in the 2-body Cross Section 36 G. Estimation of the He3()T,n)2p Cross Section 38 Chapter 71 - DISCUSSION OF EXPERIMENTAL MEASUREMENTS AND THEORETICAL CALCULATIONS ON THE 3-NUCLEON SYSTEM 39 A. Photodisintegration of Helium-3 39 B. Theoretical Cross Section Calculations 42 C. Electron Scattering on Tritium and Helium-3 43 D. Conclusions 45 Appendix A - CROSS SECTION CALCULATIONS 47 A. Chamber Efficiency 47 B. Atom Density of Helium-3 49 C. Wall Effect 50 1. Wall Loss 50 2. Spectrum Shape due to the Wall Loss 51 3. 2-body Photodisintegration Spectrum Analysis .... 53 Appendix B - THE PREPARATION OF CARBON-13 TARGETS 56 Appendix C - THE REACTION C13(p,tt)N14 AND THE MEASURE• MENT OF THE GAMMA FLUX V. 60 A. Gamma Ray Counter Efficiency 60 B. The Reaction C13(p,tt )N14 as a Source of Gamma Rays 61 • 1. Introduction 61 2. 0.554 mev Resonance 62 3. 1.75 mev Resonance 63 4. Doppler Shift 64 C. Analysis of the Gamma Spectra 65 1. 0.554 mev Resonance 65 -iv- Appendix C (cont) Page 2. 1.75 mev Resonance 67 Appendix D - NEUTRON INDUCED BACKGROUND AND NEUTRON SHIELDING 69 Appendix E - PHOTODISINTEGRATION OE HE3 NEAR THE THRESHOLD by J. B. Warren, K. L. Erdman, L. P. Robertson, D. A. Axen, and J. R. MacDonald reprinted from The Physical Review, 132, 1691 (1963) following p.72 Appendix F - GAS FLOW REGULATOR FOR AN rf ION SOURCE, by B. L. White, L. P. Robertson, K. L. Erdman, and I. R. MacDonald reprinted from The Review of Scientific Instruments, 33, 1111 (1962) following p.72 Appendix G - REMOVAL OF TRITIUM FROM HE3 by K. L. Erdman, L. P. Robertson, D. Axen, and J. R. MacDonald reprinted from The Review of Scientific Instruments, 34, 1280(1963).. following p.72 Appendix H - SIMPLE GAS CIRCULATION PUMP by K. L. Erdman J. R. MacDonald, G. A. Beer, and D. A. Axen reprinted from The Review of Scientific Instruments, 35, 241 (1964) .... following p.72 Appendix I - SIMPLE ELECTRON BOMBARDMENT APPARATUS FOR EVAPORATING BORON by K. L. Erdman, D. Axen J. R. MacDonald, and L. P. Robertson reprinted from The Review of Scientific Instruments, 35, 122 (1964) .... following p.72 Appendix J - PHOTODISINTEGRATION OF ARG0N-40 AT 9.17 AND 17.7 MEV by M. A. Reimann, J. R. MacDonald, and I. B. Warren, preprint of article to be published in Nuclear Physics, (1964) following p.72 Bibliography 73 -v- LIST OF FIGURES to follow page 1. Energy Distribution for the Sum of the Energies of the Two Protons for the Reaction He3^ ,n)2p ....... 5 2. Theoretical Estimates of the Cross Section for the Reaction He3( t ,p)D 7 3. Theoretical Estimates of the Cross Section for the Reaction He^Of ,n)2p 7 4. He3(t ,p)D and T(t ,n)D Cross Sections from Eichmann (1963) 8 5. He3()f ,p)D Differential Cross Section at 90° in the Laboratory System 11 6. Cross Sections for the Reactions He3(Y*p)D and He3()f ,n)2p from Gorbunov and Varfolomeev (1964) .... 14 7. Ionization Chamber 18 8. Details of Collector Support 19 9. Electrode Voltage Supply 19 10. Charged Particle Ranges in Gases 20 11. Effect of Purification on Voltage Pulse Amplitude ... 24 12. Chamber Energy Calibration 27 13. Chamber Background 29 14. Experimental Arrangement 31 15. Photodisintegration Spectrum, 8.06 mev Gamma Rays ... 33 16. Photodisintegration Spectrum for the Reaction He3(y,p)D at a Gamma Ray Energy of 9.17 mev 33 17. Photodisintegration Spectrum for the Reactions He3( X ,n)2p and A40( T ,«*)S35 at a Gamma Ray Energy of 9.17 mev 34 18. Cross Section for the Reactions He3(V,p)D and T(tf,n)D 36 -vi- to .follow page 19. Angular Distribution of the Reaction Products for the Reaction He3(}p,p)D .' 39 20.