Measurement and discussion of circuit time constants for radiation detectors

Objective: To measure the circuit time constants of 4 kinds of radiation survey meters (451P ionization chamber dosimeter, 6150AD6 + 6150AD - b dose meter, FH40G + FHZ672E - 10 dose meter and AT1123 dose meter) and, to discuss the formula of time response correction and its application. Methods: In the condition of continuous exposure of X-ray machine, the ambient dose equivalent rates shown by survey meters were recorded. In order to get the circuits time constant, the least squares fitting method was used to fit the data using the time response formula of circuit having a capacitance C and a resistance R in series. Results: The relative uncertainty of fitted circuit time constants was higher than 20% except for 6150AD6 + 6150AD - b dose meter. The relative uncertainty of fitted τ was 8% for 6150AD6 + 6150AD - b dose meter. Conclusions: The time required to stabilize the dosimeter readings was 8, 5, 3 and 2 s, respectively, for the 451P ionization chamber dosimeter, 6150AD6 + 6150AD - b dose meter, FH40G + FHZ672E - 10 dose meter and AT1123 dose meter. The rising trend of their measured values was not fully accordance with the RC circuit time response correction formula. (authors)