Water equivalence study of metal impregnated PAGAT gel dosimeter in terms of variation of effective atomic number

Abstract

Abstract. The aim of this study is to evaluate the water equivalency of metal doped PAGAT gel dosimeter in terms of its effective atomic number. Auto-Zeff software and NIST XCOM data base were used to perform this study. Initially Gold (Au) and Silver (Ag) were taken and divided into different concentration (from 0.01 to 100Mm) with standard PAGAT formalism and the elemental composition was determined. Using these elemental compositions Zeff was generated for photon interaction using Auto-Zeff software. Au doped gel was found as a water equivalent in the concentration range of 0.01 to 0.1Mm. Ag doped gel have matched well with water from 0.01 to 1Mm concentration in terms of water equivalence. In these concentrations, it has been concluded that metal doped gel is more water equivalent than plain PAGAT gel based on the Zeff data obtained. IntroductionEffective atomic number (Zeff) is an important parameter to consider a material to be substituted for water for radiation dosimetry [1,2]. Many researchers reported the method of finding Zeff for a compound or mixture [3,4]. Zeff of any medium depends on the energy of the incident photon beam so, a single number cannot be a representative of Zeff of a compound material [4]. Hence Zeff depends on the photon energy, it is mandatory to compute the Zeff with respect to different range of energy. There are well reported publications available regarding Zeff of different gel dosimeter [5][6][7]. As per the best knowledge of the author there is no publication of computing Zeff for metal doped PAGAT gel dosimeter [8][9][10][11]. Recently metal nano particles (MNP) are an interesting candidate for dose enhancement effect (DEE) study in gel dosimeter [12,13]. MNPs increase the probabilities of photon interaction cross sections due to their high atomic number (high Z) and yield greater secondary radiations within the gel causing DEE. Different types of MNPs were reported for gel dosimeter such as Gold (Au, Z=79), Silver (Ag, Z=47), Platinum (Pt, Z=78) and Bismuth (Bi, Z=83) [14][15][16][17] for DEE. Though DEE is a great advantage by MNPs, its high Z presence in the gel should be evaluated to consider the MNP doped gel for water equivalency. In this study, Zeff parameter was studied for evaluating the water equivalency of metal doped PAGAT gel dosimeter.