Application of solid state dosimeters to absorbed dose measurement in shallow region

The energy of radiations is imparted to the medium through the interactions characteristic of their species and the energy. The dependence of the absorbed dose on the depth in medium, called depth-dose curve, is one of the important factors in dosimetry in shallow region. Firstly, we measure the depth-dose curve of alpha-rays with using CaSO4 TLD (Thermo-Luminescence Dosimeter) with a sensitive layer of 18mg/cm2 and BeO exoelectron dosimeter with a sensitive layer of about 10-3mg/cm2. It was confirmed that the response of the former depended on the energy and that of the latter on the stopping power. As one of the applications to dosimetry in shallow region, we tried to design the TLD system for the 70 μ m dose-equivalent evaluation. A Li2B4O7 TL element with 135mg/cm2 aluminum filter give the response proportional to the 70 μ m dose equivalent for photon energies between 20keV and 1MeV with an error of about 30%. This filter acts an attenuater for low energy photons and the secondly electron supplier for high energy ones. (author)