Abstract
Harsh radiation environments are characterised by high temperature, high radiation fluence high pressure and sometimes vibration. These conditions are present in nuclear reactor cores and oil and gas prospecting. Because of the limited supply of 3He, new materials are needed for neutron porosity measurements in order to reduce the cost of nuclear well logging and reduce dependence on 3He. High radiation fluence affects material's performance for radiation detection applications. For decades silicon has been an important material for radiation monitoring because of its cost effectiveness and relative availability. In recent years, the level of radiation produced in high energy physics (HEP) experiments has drastically increased, which compels searching for special materials that can withstand high radiation fluence. On the other hand, silicon carbide (SiC) devices have also been receiving considerable attention because of their properties that make them excellent candidates for harsh radiation media applications. The main aim of this work was to investigate the thermal neutron detection ability of SiC diodes covered with standard LiF neutron converter layers at elevated temperatures up to 500 K for extended periods of time - up to 100 hours. For this purpose, a range of 4H- silicon carbide(SiC) devices, based on semi-insulating bulk material and epitaxial diodes has been characterised in terms of current voltage, capacitance voltage and alpha spectroscopy performance as a function of temperature to underpin the neutron tests with an understanding of changes in Schottky Barrier Height, conductivity and effective doping with temperature before proceeding to neutron tests. In parallel, a series of Silicon (Si) Schottky diodes was also studied with various levels of proton induced radiation damage as part of an international collaboration. LiF coated non-damaged devices have served as a benchmark for the SiC tests at room temperature. It was found that all epitaxial SiC devices tested exhibited an increased effective dopant density due to increased activation of dopants with increasing temperature, leading to some reduction in depletion width, and hence active thickness as well as to an increase in leakage current. Nevertheless, leakage currents only compromised the energy resolution of alpha particle spectroscopy (within the limitations of the set-up) at the highest applied bias voltages. Long term stability tests indicate that the devices respond in a stable manner within 8 hours of operation or less and, maintain performance for at least 24 hours. Stability is reached faster at higher temperatures. So far, the silicon devices show attractive response to alpha radiation and confirm their possible applications for hard radiation detection at room temperature including the large hadron colliders (LHC). The alpha particle detection and its stability at high temperature demonstrated by SiC samples is an indication of their suitability in harsh radiation detection applications. In addition, their neutron detection and its stability imply future application in oil and gas prospecting and nuclear reactor monitoring.