Study Of Production Of Secondary Particles And Neutrons From Heavy Targets In Nuclear Reactions

A study of the mechanism of nucleus-nucleus interactions at intermediate energies (1-5 GeV/nucleon) is presented. The data were obtained by irradiation of heavy targets with relativistic beams at the JINR Synchrophasotron and other accelerators. In the experiments, beams of p, d, He and C nuclei and targets of Cu, Pb, U were used. Studies of nucleus-nucleus interactions were performed by measuring the yield of secondary particles with registration of induced activity in massive targets using the activation technique and the gamma-spectrometric method. Apart from the gamma-spectrometric equipment, solid SSNTD detectors have been employed to obtain the data. Measurements of heavy fragment production, assessment of neutron spectra by using the SSNTDs with different filling agents, as well as searching of the coloured states, have been carried out by means of these detectors. Analysis of these data allows us to say that the main cause of disagreement between experiment and theory is that no collective effects were taken into account in nucleus-nucleus collisions and may also be a change of the reaction mechanism in this energy region. The last statement is supported by an essential difference in characteristics of single particle and cluster distributions in hadron-nucleus and nucleus-nucleus interactions and also by enhanced yield of strange particles and antiprotons in nuclear reactions. A similar picture (i.e, discrepancy between theoretical predictions and experimental data) is observed while studying neutron yields accompanying irradiation of heavy targets with relativistic nuclei. Besides fundamental information, experiments with neutrons provide vaIuable data to carry out calculations on the actual problem of accelerator breeding and transmutation of long lived radioactive isotopes. Using this information, we found (in 1996) 10 and 140 barns for the transmutation cross-section of I-129 and Np-237, respectively.