Radiation monitoring in Mrad range using radiation-sensing field-effect transistors

In many of the recent e+e- particle physics experiments, monitoring of the accumulated dose in silicon is essential to maximize the lifetime of silicon vertex detectors operating in severe radiation environments. Using radiation-sensing field-effect transistors (RadFET) as radiation monitoring devices, we studied their responses during irradiation and during subsequent annealing. The relation between the RadFET response and the dose was determined by irradiations with a 60Co source with known activity. The study of annealing at three different temperatures showed that RadFETs gradually anneal for up to 40%. Annealing can be fitted by a sum of two exponential functions with time constants of 3 and 85 days.