Modified general cavity theory applied to the calculation of gamma dose in⁶⁰Co thermoluminescence dosimetry

Abstract

Burlin's general cavity theory for intermediate sized cavities incorporated two weighting factors: d, the average reduction in the electron fluence from the medium inside the cavity, and 1 - d, the average fractional build-up to equilibrium of the cavity-generated electron spectrum--both calculated for an average path length g of electrons crossing the cavity. A new weighting factor d' has been introduced expressing the fact that average path length for medium- and cavity-generated electrons are not equal and this leads to a modified general cavity expression. The new expression is applied to 60Co thermoluminescence dosimetry experimental results of other workers. For LiF TLD in all the media agreement with experiment is improved. There is a significant dependence of the theoretical results on the effective mass attenuation coefficient, indicating the need for further studies.

The quality dependence of LiF TLD in megavoltage photon beams: Monte Carlo simulation and experiments

“…where d is a weighting factor which gives the contribution to the total dose of medium generated electrons and (1 − d) is the contribution to the total dose from electrons generated by photon interaction in the cavity. Burlin's cavity equation has been critically examined and modified by Horowitz et al (1983) and Almond and McCray (1970). Other authors like Kearsley (1984) have proposed a new cavity equation.…”

Application of cavity theory to the response of various TLDs to gammas degraded in water

“…This value of β together with g = 1.2t (t is dosimeter thickness in g cm −2 ) was used by Ogunleye et al (1980) for LiF stacks surrounded by different materials and irradiated with 60 Co gamma rays. For the same irradiation conditions Horowitz et al (1983) used the values 16.26 cm 2 g −1 for β (derived from Loevinger's expression for air), and g = 1.539t, calculated using the Klein-Nishina electron angular probability distribution function. Horowitz and Dubi (1982) proposed a simple modification of the Burlin general cavity theory for photons.…”

Application of Monte Carlo simulation to cavity theory based on the virtual electron source concept

“…It is particularly useful in relation to solid-state dosimeters, which typically have dimensions that are comparable to the ranges of the electrons present. However, the Burlin theory ignores all secondary electron scattering effects, resulting in large discrepancies between the predicted doses to the cavity and the experimental results in high atomic number media (Horowitz et al 1983, Kearsley 1984. Haider et al (1997) have developed a new cavity theory based on the Burlin theory that includes the effects of secondary electron backscatter from the interface.…”