High-Flux Experiments and Simulations of Pulse-Mode Position-Sensitive CdZnTe Pixelated Detectors.

Abstract

In recent years, operation of CdZnTe detectors under high photon flux irradiation has been pursued by many research groups. However, under high-flux scenarios, these detectors are limited by poor hole transport properties and other factors, causing the build-up of positive space charge as a function of irradiation flux and time, the so-called polarization effect. In this work, high-flux experiments and simulations were conducted to study this problem. In simulations, charge drift calculations were carried out by numerically solving the charge continuity equations coupled with Poisson's equation, assuming multiple electron and hole defect levels. A simplifed 3D axisymmetric model was implemented in order to reduce computational time and enable simulation of more advanced physical processes. Electron and hole transport properties used in simulations were measured by irradiating the detectors with Gamma-rays, alpha particles and K alpha X-rays. Experiments were conducted using a JL Shepherd & Associates 3 Ci (09-20-2001) Cs-137 Gamma-ray irradiator and a custom-built experimental apparatus. A series of experiments were conducted at different applied cathode bias voltages. More importantly, in this work we have developed a complete 3D framework that can be extended to other semiconductor detector materials to study and predict their performance under high-flux scenarios.