PURPOSE: To measure a minute quantity of radiation under a much fluctuating background with a high precision, by performing the measurement in two positions, where the relative distance between a sample and a detector is different, alternately many times in a short time.
CONSTITUTION: A sample 2 is put in a shelter 4 and is set on a sample moving device 8. The measurement for the radiation from the sample is perfomred in two positions, a measure sample position A and a measure sample position B alternately many times for every prescribed time Δt. Measured values of the dose of radiation for relative distance L and M (L<M) are obtained as shown in expression (1). In expression (l), (n) is the number of times of measurement. A ratio 1:α of the dose of radiation for relative distances L and M which is obtained preliminarily by using a standard radiation source of a large dose of radiation is used to obtain a dose of radiation for the relative distance L as shown in figure (2). In expression (2), K is count efficiency.
KAMIYA KUNIO
FUJII MASAAKI
