A Novel Fast Readout, Gamma Detector System for Nuclear Fingerprinting

<div>Technical paper presented at the 2017 Defence and Security Doctoral Symposium.</div><div><br></div><div>In order to be effective, decommissioning of nuclear facilities as well as recovery procedures following a nuclear accident require a precise estimation of the amount, type, and topological distribution of nuclear material present at the scene. </div><div><br></div><div>In this work we present a novel, fast readout, spectroscopy system suitable for high radiation level environment which we estimate to be 10 times faster than current deployed systems.</div><div><br></div><div>The proposed device is based on semiconductor materials: when hit by a photon they generate electron-hole pairs, which in turn give rise to a current pulse that is proportional to the incident photon energy. This mechanism allows recognizing the incident radiation source. The proposed apparatus is composed of five semiconductor materials (Silicon, Gallium Arsenide, Uranium Dioxide, Cadmium Zinc Telluride and Diamond), which allow the cover the detection of a wide range of energies. This multi-material platform enables the precise identification of 27 isotopes which can be found after a nuclear accident or when a nuclear plant is in decommissioning. </div><div>The amplifier stage uses the Amptek A250 charge sensitive preamplifier which shows low-noise (<100 electrons rms) and fast (rise time 2.5 ns) response behaviours. The readout chain consists of a MAROC3 chip and an FPGA (field programmable gate array). </div><div><br></div><div>To prove the validity of the system, several Monte Carlo simulations, using Geant4, were performed. Simulation results have shown that gamma spectroscopy and material abundance study are possible. The system is under test at the present.</div><div><br></div>