Date of this Version
Thesis–degree of Doctor of Philosophy—University of Nebraska—Lincoln, 1964. Department of Physics.
Bombardments of nominally 99.995% pure copper foils at 77° K have been performed using 50 to 325 keV protons and He+ ions from the Nebraska Cockcroft-Walton accelerator. Rates of defect production as a function of energy were calculated from measured electrical resistivity changes for each type of ion. Comparison of our experimental values, corrected for low temperature annealing, with the Harrison-Seitz and Neufeld-Snyder theoretical defect production rates show that theory predicts values 10 to 12 times higher than our measurements at 50 keV for both ions. Agreement becomes better at higher energies with the discrepancy about a factor of 2 to 4 at 300 keV. The relationship between experimental and theoretical values for the defect production rates was found to be linear. For incident protons the relationship is n(EXP.) = 0.319 (n(THE.) – 15.3) and for incident He+ ions n(EXP.) = 0.604(n(THE.) – 55.1), where n is the number of defects/incident particle. Various possible reasons for the disagreement between theory and experiment are discussed.
Advisor: Edgar A. Pearlstein