A study of radiotherapy dosimeters based on diamond grown by chemical vapour deposition

Natural diamond has been investigated as a radiotherapy dosimeter with good results. However, the lack of readily available 'detector grade' natural diamonds make their application in this area difficult. Advances in the production of diamond by chemical vapour deposition (CVD) allow material with good electronic properties to be fabricated routinely. In this paper, results from the characterisation of radiotherapy dosimeters based on polycrystalline CVD diamond using 250 kV X-rays are presented and compared with the performance of commercially available Si and natural diamond dosimeters. The devices are sandwich structures with Cr/Au metalisation on both faces. Despite the low carrier lifetimes and large electron-hole pair creation energy, their sensitivity is found to be greater than 2 nC/cGy, comparable to Si dosimeters. The response of the devices is linear with dose, but non-linear with dose rate. The response to radiation is observed to increase with dose by similar to 20% initially, the so-called priming effect. (C) 2000 Elsevier Science S.A. All rights reserved.