Conceptual Design and Simulation of Alpha-Beta Detector for Surface Contamination Measurements

The radioactive contamination measurement is essential in nuclear facilities. Monitoring of low level alpha and beta contamination is possible using light detectors high efficiency. Due to the fact that many detectors canchr('39')t simultaneously discriminate alpha, beta and gamma rays; among existing methods, phoswich detectors would be appropriate option to measure different radioactive contaminations. By this method, it is possible to study simultaneously the alpha/beta/gamma contamination sources with a single detector, which consists of three layers of different scintillators. Here, our design using ZnS(Ag), BC400 and NaI(Tl), with thicknesses of 0.0025, 1 and 3 cm, is sensitive to interaction with alpha, beta and gamma particles, respectively. The absolute efficiency for each layer was determined by the trade-off between the efficiency and background counts due to interference radiation in each layer. Thus, at an energy of 0.1 MeV, the maximum absolute efficiency for beta particles was 24% and 1-2 MeV at maximum absolute yield of gamma rays with an approximate value of 16%.