Verification of physical parameters of insity p-type HPGe detector by scan method using collimated low energy photon beam and MCNP simulation

Abstract

In this work, the physical dimensions and the actual position of germanium crystal within a detector housing, the homogeneity of the crystal surface and outer dead layer thickness for a p-type HPGe detector were confirmed by the scan method using the collimated low energy photon beams combined with Monte Carlo simulation. The length and the diameter of the crystal were found to match with the values supplied by the manufacturer in discrepancy of about 3%. Only one mounting strap (Typical) for holding the crystal inside the mounting cup instead of two which is indicated in the detector drawing supplied by manufacturer was revealed by scanning along the lateral face of detector. Scanning on the front surface and around the lateral face of detector by the collimated 59.5 keV photon beam verified the outer dead layer thicknesses at the front surface and lateral face of the crystal averagely increases about 6.5% and 12% respectively. Adjusting the detector parameters for MCNP simulation by these verified values, the simulated peak efficiencies for different photon energies become being in accordance with the experimental peak efficiencies.