Studies on gamma ray inter- action parameters of selected thermoplastic, biopolymer and rare earth oxide samples

Abstract

The extensive use of radiation in various fields such as medical physics, in- dustry, space research, radiation shielding, dosimetry etc. necessitates the knowledge of the parameters associated with the interaction of radiation with materials. As part of the present work, we have determined theoretically, the mass attenuation coefficient, effective atomic number and electron density of selected thermoplastic and biopolymer samples, having medical applications, for total as well as partial gamma ray interaction processes in the wide range of energies 1 keV to 100 GeV. The mass energy-absorption coefficient, the effective atomic number corresponding to gamma ray energy absorption in these media and the kerma relative to air of these polymers were also estimated for the energy range of 1 keV–20 MeV. Variation of these parameters with photon energy and chemical composition of polymers has been studied. The estimated values were compared with experimental data, wherever available, and these show good agreement. The effective atomic numbers of these polymers obtained by different methods have been compared in various energy regions and possible conclusions were drawn. We have also estimated the radiation interaction parameters of selected chemotherapy drugs administered concurrently with radiation therapy in the energy range 1 keV to 100 GeV by using the EpiXS program. The radiation response of the selected drugs have been compared at different energy regions.Except at absorption edges, the selected drugs have shown similar interaction parameter variations with photon energy. We have also determined the angle integrated total scattering cross sec tions of some rare earth oxides experimentally for 59.54 keV and 662 keV gamma rays in the angular ranges of 0–4 0 , 0–6 0 , 0–8 0 and 0–10 0 . From the experimental total scattering cross sections, the corresponding angle integrated incoherent scattering cross sections obtained from ENDF library (based on the non-relativistic Hartree – Fock form factor method) was subtracted to obtain the angle integrated coherent scattering cross sections. The angle integrated coherent scattering cross sections show good agreement with that determined from ENDF data. The effective atomic numbers of the selected rare earth oxides were extracted by applying the ratio of cross section method. The variation of angle integrated coherent scattering cross section with the effective atomic number of the selected compounds have been studied. In addition, some attenuation measurements have been carried out on edible oil samples using 662 keV gamma rays. Here, wehave determined the mass attenuation coefficients, from which the effective atomic numbers were deduced. The variation of interaction parameters with the composition of the food samples were also studied.