Contribution to the study of the fundamental physical parameters (stopping power, ionization potential and energy straggling) describing the slowing down of heavy ions in solid material

Abstract

Conceptually the complex phenomenon of the slowing down of energetic charged particles through matter is described bytwo physical fundamental parameters, the stopping power and the energy straggling. The average energy loss of an ion per unit path length when it is crossing the matter is called the stopping power. At the same time the energy transfer during the collision between the ions and the target atoms follows a statistical behavior which gives rise to fluctuations in energy loss,theaverage square fluctuation (standard deviation) of the energy loss distribution is commonly called the energy straggling. Multitude contemporary applications of ion beam such as ion beam analysis, ion material modification, nuclear physics, radiology etc., requires a precise determination of the stopping power of heavy ions in a matter as well as an accurate measurement of the energy straggling.These two fundamental parameters have been studied experimentally and theoretically since the beginning of the 20th century.Whereas experimental and theoretical data are readily available for Helium and proton ions, the data are much scarcer for heavy ions and significant discrepancies are reported by different authors especially at low energies. In the basis of Lindhard, Scharff and Schiott (LSS) formula and by inserting the effective charge a new semi empirical expression has been proposed and tested for better stopping power calculations of heavy ions in various solid targets at low energy range (0.1-1MeV/n).This new proposed expression exhibits a good agreement with H. Paul's electronic stopping power database Within the framework of this thesis we adopted a nuclear technique based on measurement of the flight time of the recoil ions produced by the interaction of ions beam (84Kr, 63Cu) of energy of 26 MeV, with a primary target for the measurement of the energy loss of heavy ions (3 ? Z1 ? 14) in a thin layer to deduce the stopping force and the energy straggling.The obtained values of stopping force are compared with the predicted values obtained from the Stopping and Range of Ions in Matter program SRIM-2013, Lindhard-Scharff-Schiott (LSS) formula, available experimental data from the literature and the new proposed semi empirical formula. The energy stragglingvalues are compared with theoretical prediction of the Bohr straggling, straggling deduced from the Bohr stopping power model, and the corrected Lindhard-Scharff formula by introducingthe bunching effect according to the Besenbacher approach. The aim of such comparison is to check the reliability and accuracyof the existing energy loss straggling formulations, in the light of the present experimental results.The experimental results of energy loss straggling of all ions are found to be greater than those predicted by the Bohr stopping model or Lindhard-Scharff prediction model. The introduction of the bunchingeffect improves the comparison and gives an estimation of other effects such as charge exchange effect