A study of gamma attenuation parameters in poly methyl methacrylate and Kapton

Poly methyl methacrylate (PMMA) and Kapton polyimide are polymers used for various aerospace applications. We have measured the gamma attenuation parameters such as mass attenuation coefficient, effective atomic number and electron density of PMMA and Kapton polyimide for various gamma sources of energy ranging from 84 keV to 1330 keV (170Tm, 57Co, 141Ce, 203Hg, 51Cr, 113Sn, 22Na, 137Cs, 60Co, 22Na and 60Co). The measured values agree with the theoretical values. In the present work, we have also computed energy absorption build-up factors and exposure buildup factor of PMMA and Kapton polyimide for wide energy range (0.015-15 MeV) up to the penetration depth of 40 mean free path using Geometrical Progression fitting method. The values of these parameters have been found to change with energy and interaction of gamma with the medium. The present study on gamma attenuation parameters are expected to be helpful in dosimetry, radiation shielding and other radiation physics based applications. The experimental data on the mass attenuation coefficients for Kapton and PMMA is not available in literature. To my knowledge data available e.g. in the NIST data base are based on extrapolations from the measurement of mass attenuation coefficients for the elements. Hence this work is first of its kind and it is useful in the various field of Polymers.