2016 年 15 巻 1 号 p. 66-73
The energy spectra and dose equivalent rates (H1cm and H70μm) of direct and scattered X-rays from various targets of X-ray generation equipment were measured by three kinds of radiation monitors: an ionizing chamber, a GM survey meter and a CdTe semiconductor.
The effective energies of direct X-rays from Cr and Cu targets applied at 40 kV are 8.1 keV and 11.6 keV, respectively, which are larger by about 2-3 keV than the energy of each characteristic Kα X-ray. The effective energies of direct X-ray from Mo, Ag and W targets at 40 kV are 17.1 keV, 14.5 keV and 13.4 keV, respectively, which are lower than the energy of each characteristic Kα X-ray. On the other hands, the effective energies of scattered X-rays from all targets are almost the same (12.4±0.34 keV) because the scattered X-rays are affected by fluorescent X-rays of Pb and Sn on shielding glass. The calibration factors to convert from count rates to dose equivalent rates (H1cm and H70μm) were obtained for a wide mouthed GM survey meter and a CdTe semiconductor. The above results enable us to easily estimate the low dose equivalent rates for leaked or scattered X-rays of X-ray generation instruments.
