Rekonstrukcja pierwotnych fragmentów zderzeń ciężkich jonów przy pośrednich energiach

Abstract

The main process describing heavy ion collisions at intermediate energies, in range of 20-100 MeV/A, is multifragmentation. During the heavy ion collision, a variety of excited, primary fragments are produced. As a result of the deexcitation process, the final, secondary reaction products are formed. Due to the violence of the collision the process is very fast and the live-times of the primary nuclei are very short. Hence, is not possible to experimentally detect primary fragments. Therefore, significant research into methods of determination of the type of primary fragments (eg. mass and charge) with the knowledge of experimentally measurable secondary fragments, are necessary. In this thesis, the time evolution of reaction 40Ar+124Sn at beam energies: 15, 24, 30, 37 and 47 MeV/A, were studied. The analysis estimate the time reaction: τ=300 fm/c as sufficient for the primary fragments formation. Based on the impact parameter estimation, a proper group of central collisions (b≤3 fm), were selected to the further analysis. The main part of the thesis was development of the reconstruction procedure of primary fragments in heavy ion reaction at intermediate energies. It is based on the correlation between secondary intermediate mass fragments and the light particle emission (n, p, d, t, 3He, 4He). The simulation of reaction 40Ar+124Sn at 47 MeV/A, were prepared by using the QMD and AMD models in case of primary fragments, and for secondary fragments via GEMINI and cooler codes. Moreover, database of light particles formed during evaporation process together with primary intermediate mass fragments in range of Zε<3,19> and excitation energy equals E*/A=4.5 MeV, were prepared. As a result, the primary reaction fragments with different neutrons to protons ratio for 64Zn+197Au, 64Zn+92Mo and 40Ar+124Sn at 47 MeV/A, were reconstructed. The method of selecting the multiplicity of light particle (directly from distribution or Gaussian fit function) and the number of reconstruction as well as the number of isotopes that construct the light particle multiplicity database, were considered.