Study on the measuring method of skin contamination by pu compounds, using multi-hole-collimator for α-raydetection.

Abstract

Theoretical and experimental studies on the multi-hole-collimator for α-ray detection are described. By using the collimator of lucite in 2mm thickness having a great number of holes of 0.5mm diamater directly in front of scintilation detector, it has been found possible to measure α-rays passing through the absorbent layer up to 95% of its range (about 40μ in tissue) with constant efficiency of 0.3%. In addition, by measuring α-ray spectrum, it is possisle to determine the distribution in depth of the source material. The resolution in this case is about 5% of the range of α-rays (about 2μ) in full width at half maximum. The measuring efficiency in using the multi-hole collimator, the resolution for the distribution of thickness in absorbent layer, and the maxmum thickness in which constant efficiency for measuring is obtained are analysed and solved theoretical as a function of variables determined by ratio of the diameter of the hole and thickness of collimator, and was identified in experiments good agreement in values. The less the ratio of the diameter of hole and the thickness of collimator, becomes, the longer maximum allowable absorbent layer for counting with constant efficiency become, and the better the resolution become, but the less in the efficiency of measuring are obtained.