Application of pMOS dosimeters in low-field mode for radiation dose measurements which could be used in radiotherapy

Abstract

The pMOS do sim e ters sen si tiv ity (Tyn dall Na tional In sti tute, Cork, Ire land) to gamma and X-ray ir ra di a tion and 2000 h fad ing at room tem per a ture is pre sented. The ra di a tion fields were cre ated us ing a 60 Co source for two dose ranges (1-5 Gy and 10-50 Gy) as well as for X-ray units of a 280 kV spec trum for a sin gle dose range from 0.1 to 1 Gy. Ir ra di a tion was performed in low-field mode (no gate bias dur ing ir ra di a tion, V irr = 0 V), sen si tiv ity char ac terized by the thresh old volt age shift as a func tion of the ab sorbed ra di a tion dose and time af ter ir ra di a tion. Lin ear de pend ence be tween the thresh old volt age shift and the ab sorbed ra di ation dose was only es tab lished for pMOS do sim e ters which were ir ra di ated by gamma rays in the dose range of 1 to 5 Gy. Ob tained re sults show that the sen si tiv ity of these com po nents is much higher in case of X-ray ra di a tion than in that of gamma ray ra di a tion. More over, the fading of ir ra di ated pMOS do sim e ters with X-rays is higher than in the ones ir ra di ated with gamma rays.