γ励起螢光X線の転換収率

抄録

In order to estimate the quantity of fluorescence X-rays from a specimen irradiated with high energy γ-rays, the conversion yield of fluorescence X-rays was measured for plane targets and a beam of γ-rays from Cs-137source. Several procedures were followed to determine the absolute yield experimentally. The angular distribution of the yield and the intensity ratio of fluorescence X-rays to scattering γ-ays emerging from a lead target were also measured, as well as the vari-.ation of the yield with target thickness. It was shown that the backward yield finally saturates at a thickness corresponding to a few mean free paths of backscattering γ-rays, not of fluorescence X-rays. From this result the enhancement of the yield is considered to be mainly due to excitation by the scattered γ-rays within the target. Calculations of the yield were made for excitation by incident r-rays and by singly scattered γ-rays in the target. The approximate calculation roughly coincided with the experiment, but complete agreement was not obtained even though the inclusion of the enhancement effect of secondary electrons. It seems to be necessary that excitation by multiple scattering γ-rays is taken account of in the yield calculation.