Gurdeep S. Sidhu

A study of energy and effective atomic number dependence of the exposure build-up factors in biological samples

A theoretical method is presented to determine the gamma-radiation build-up factors in various biological materials. The gamma energy range is 0.015-15.0 MeV, with penetration depths up to 40 mean free paths considered. The dependence of the exposure build-up factor on incident photon energy and the effective atomic number (Zeff) has also been assessed. In a practical analysis of dose burden to gamma-irradiated biological materials, the sophistication of Monte Carlo computer techniques would be applied, with associated detailed modelling. However, a feature of the theoretical method presented is its ability to make the consequences of the physics of the scattering process in biological materials more transparent. In addition, it can be quickly employed to give a first-pass dose estimate prior to a more detailed computer study.

Effect of collimator size and absorber thickness on gamma ray attenuation measurements

Mass attenuation coefficients have been measured in extended media of soil and water for 662 keV gamma rays under different collimation conditions. A correlation effect due to absorber thickness and collimator size has been observed.

VARIATION OF BUILDUP FACTORS OF SOILS WITH WEIGHT FRACTIONS OF IRON AND SILICON

Abstract The effect of weight fractions of Fe and Si on buildup factors has been studied in five different soils. The chemical composition is seen to influence the buildup factors at lower energies only. At energies greater than 0.40 MeV, the buildup factor values are more or less independent of chemical composition of soils.

Buildup factor studies of HCO-materials as a function of weight fraction of constituent elements

Abstract The effects of fractional abundance of constituent elements have been investigated on the energy absorption buildup factors of HCO-materials for some incident photon energies at a fixed penetration depth of 20 mfp. At low incident photon energies, a change in buildup factor is seen whereas buildup factor values of HCO-materials are independent of fractional abundances of H, C and O for high energies.

A study of transmitted photon spectra of 133Ba through a soil medium

Abstract The transmitted photon spectra of 133Ba gamma rays have been recorded and studied as a function of dimensions of a soil medium. In these studies a multiple-scatter peak is observed in the soft part of the spectrum. The longitudinal thickness of the soil medium is seen to affect only the intensity of the peak, whereas the variation in transverse thickness affects both the intensity and energy of the peak. A reversal of the trend of the multiple-scatter peak intensity to increase with transverse thickness occurs as the longitudinal dimension increases.