A novel gamma dosimeter applied a modified coherent demodulation technique

We have developed a novel gamma dosimeter in which a modified coherent demodulation technique is used for increasing the dosimetric sensitivity. The dosimeter probe consists of a 20 mm-thick collimating Pb-disk, five pairs of CsI(Tl) scintillator-photodiode detectors and five preamplifiers, which are housed in a cylindrical Al-tube. The disk placed just in front of five detectors has four circular-windows which differ in diameter so that the amounts of gamma component entering each detector are controlled. The gamma intensity (dose rate) is evaluated with the cross correlation power spectrum density between the count rate of detector signals and the area of the windows of the disk. The background component was statistically reduced to about 1/63, and then, gamma rays of 0.056mR/h= 1.44 × 10 −8C/kg/h could be detected against a background of 3.52mR/h = 90.8 × 10 −8C/kg/h.