MCNP analysis of a multilayer phoswich detector for β-particle dosimetry and spectroscopy

To measure and study energy deposition of β-particles at different depths, a triple-layer phoswich detector has been designed. The phoswich detector consists of BC-400/CaF2:Eu/BC-444 with decay time constants of 2.4, 940 and 264 ns, respectively, all with thicknesses corresponding to that necessary to completely stop 0.1 MeV electrons in the first layer, 1.0 MeV electrons in the second layer and 2.5 MeV electrons in the third layer. Monte Carlo N-Particle (MCNP) version 4B was used to simulate energy deposition in each layer from monoenergetic β-particles. The simulations and measurements revealed that the traditional rise time measurement technique is not able to provide appropriate and accurate pulse shape discrimination for this type of detector.