PURPOSE: To simplify the measurement of density and density distribution in a plate-shaped object, by setting the direction of application of a gamma ray and the direction of detection of a scattered gamma ray so that a line absorption coefficient and an effective line absorption coefficient of the gamma ray be equal with respect to a primary gamma ray and the scattered gamma ray.
CONSTITUTION: An angle 23 at which a primary gamma ray 22 is made to fall from a gamma ray source 20 on a plate-shaped sample 10 and an angle 33 at which a radiation detector 30a detects a scattered gamma ray 32 scattered at a Compton scattering angle 34 in a measuring area 11 are set so that an effective line absorption coefficient of a gamma ray defined by the ratio between a line absorption coefficient of the gamma ray and the cosine of an angle formed by a gamma-ray transmission path and the direction (x) of the thickness of the sample 10 be equal with respect to the primary gamma ray 22 applied to the sample 10 and the scattered gamma ray 32. As for an output of the radiation detector 30a, the scattered gamma ray for a prescribed time set beforehand is counted by a scattered gamma ray counting device 40a and stored in a storage device 50, and as for an output of a radiation detector 30b, the primary gamma ray is counted by a primary gamma ray counting device 40b and sent to a density computation device 60. The density is computed from the intensity of the scattered gamma ray stored in the storage device 50 and from the transmission intensity of the primary gamma ray and outputted to an output device 70.
KAMATA SHOJI
KANAMORI TAKAHIRO
IZUMI SHIGERU
YABUKI TAKASHI
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