Development of radiation hard Silicon Carbide (SiC) neutron detectors - CASE award with AWE

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The aim of the project is to develop a new generation of radiation hard fast neutron detectors using SiC, and to assess their performance as a gamma-blind fast neutron detector in high flux photonuclear reactions. This work is collaboration with the Threat Reduction Department at AWE, and aims to transfer a new detector technology from the University which is optimsed for use in their photonuclear material interrogation programmes. The projecrt benefits from the existing STFC funded detector R&D at Surrey for radiation hard heavy ion detectors (eg. diamond) for nuclear physics experiments at GSI. Photonuclear material interrogation is a promising method for future threat reduction programmes. Here we propose to develop a new fast neutron detector based on the compound semiconductor SiC. The unique properties of SiC combine room temperature operation, extreme radiation hardness, high neutron sensitivity, and gamma-blind performance. It is therefore ideal for neutron detection in high-flux mixed n/gamma fields. In 2008 a break through in SiC material quality from Cree Inc has now made available free-standing wafers of electronic grade SiC, of the quality required for radiation detectors. We propose to fabricate prototype SiC detectors at Surrey's detector laboratories, and then test their performance at AWE and NRL test facilities. Various active interrogation methods for threat reduction and SNM detection are currently being developed, including nuclear resonance fluorescence and active neutron interrogation. In such cases, the ability to accurately measure the neutron fluence emitted from a test object is crucial, often in the presence of a strong mixed neutron-gamma field. In particular, the use of a pulsed neutron beam to create prompt neutron activation (PNA) is a promising technique for the interrogation of shielded SNM. In this technique, short neutron bursts of duration 100-200 us are used to generate fast fission neutrons from the interrogated material. The presence of lead, cadmium or hydrogenous shielding materials around the SNM produced short decay times for the emitted neutrons, due to their thermalisation and capture. Therefore the success of the PNA technique requires use of neutron detectors that have a rapid response and are sensitive during the period immediately after each incident neutron burst. Prototype SiC detectors have recently been demonstrated as a compact semiconductor-based fast neutron detector. In general, semiconductor-based neutron detectors should fullfill the following criteria: - High sensitivity to fast neutrons, with gamma-blind selectivity to reject photon events. - Compact detectors capable of operating at room temperature, with the potential to scale-up to large active areas. - Radiation hard detectors which are capable of withstanding significant neutron/gamma dose. SiC offer particular advantages over silicon detectors, principally in its superior radiation hardness, and its ability to operate in extreme environments at eleavated temperatures. Direct funding from AWE's (value ~£30k) has been approved to support the CASE partner activities within this project. This money will cover the additional CASE student stipend plus plus the provision of consumables for the project (mainly purchase of SiC wafers). The student will spend approximately 1 week per month at AWE, and will establish a collaborative partnership between the Threat Reduction group at AWE and the Detector Physics group at Surrey.