REACTION MECHANISMS IN HELIUM-3 INDUCED PROJECTILE BREAKUP: A STUDY OF BREAKUP-RELATED PROCESSES INDUCED BY HELIUM-3 PARTICLES AT E(HELIUM-3) = 52 MEV.

摘要

Inclusive proton and deuteron spectra from He induced reactions on ('12)C, ('28)Si and ('58)Ni have been studied. Each spectrum contains a continuum part that may be separated into a broad bump, centered around beam velocity energies at forward angles, and an exponential tail. The properties of each of these components have been investigated as function of outgoing particle, detection angle and target mass. The centroid position of the bump and the bump width are found to be almost independent of target mass and detection angle. The total (energy and angle integrated) cross sections for the bump show a mass dependence almost proportional to A('2/3) for both protons and deuterons. The total cross section for the tail has a different mass dependence for protons and for deuterons: proportional to A and A('1/3), respectively. Results for the proton tail are qualitatively reproduced by calculations assuming absorption of the projectile. Additionally measured inclusive triton spectra show a similar composition (bump - tail).;A semi-empirical model is presented that allows the calculation of the relative coincidence yields from the total inclusive cross sections. The total projectile breakup cross section amounts to about 20% of the total reaction cross section.;A quasi-free breakup model is proposed for the description of the breakup spectra in terms of a spectator-participant approach. The model reproduces the data qualitatively very well. (Abstract shortened with permission of author.).;Charged particle-proton coincidences have been measured and analysed in order to identify the major contributors to the inclusive proton, deuteron and triton spectra at 10(DEGREES). The following processes have been identified: (i) elastic and inelastic breakup in which the projectile breaks up into two constituents leaving the target in its ground state or an excited state, (ii) breakup transfer in which the projectile breaks up in two components combined with one-nucleon pickup by one of the components, (iii) absorptive breakup in which one part of the projectile continues virtually undisturbed while the other part is captured followed by statistical emission of protons, and (iv) processes resulting in preequilibrium emission of deuterons or tritons followed by statistical emission of protons. These processes account for 75 - 100% of the inclusive cross section.