Study evolution of fragment energy spectrum in compound and elemental absorber with thickness via effective charge correction

The energy loss behaviour of fission fragments (FF) from $^{252}$Cf(sf) in thin Mylar ($H_8 C_{10} O_4$) and Aluminium absorber foils have been revisited. The aim is to investigate the observed change in the well known asymmetric energy of spontaneous fission of $^{252}$Cf as the fragments pass through increasingly thick absorber foils. Two different types of absorbers have been used: one elemental and the other an organic compound. The stopping powers have been determined as a function of energy for three fragment mass groups with average masses with $<A>$ = 106.5, 141.8, 125.8 corresponding to light, heavy and symmetric fragment of $^{252}$Cf. Using the effective charge (Z$_{eff}$) in the stopping power relation in the classical Bohr theory best describes the stopping power data. Spectrum shape parameters, subsequently have been extracted from the energy spectra of fission fragments for different foil thickness. The effective charge (Z$_{eff}$) correction term determined from the stopping power data is then used in the simulation for the absorber thickness dependence of the shape parameters of the energy spectrum. The present simulation results are compared with the TRIM prediction. The trends of the absorber thickness dependence of the spectrum shape parameters, for both Mylar and Aluminium are well reproduced with the present simulation.