Absolute Dose Rate Measurement of Very Soft and Weak X-rays by Means of a GM-counter

Abstract

In order to determine the dose rate of X-rays having energies lower than 35 keV, a method that counting rate determined with a GMcounter was converted to dose rate was investigated. A radiation field of which intensity is near background can be measured by this method. Conversion coefficients from counting rate to dose rate were calculated as a function of photon energy for some GM-tubes available in Japan. The characteristics of the conversion coefficient were examined and the nature of GM-tube favorable for monitoring was discussed. By the proposed method a continuous X-ray field can be measured with a satisfactory accuracy and a precision of about 5%. The method can be applied to the determination of absorbed dose rate as well as exposure dose rate.