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Diamond has been regarded as a promising radiation detector material for the use as a solid state ionising chamber for decades. To improve detection performance, the parameters affecting the charge transport need to be understood, especially defects leading to degradation from the expected behaviour of an “ideal” crystal. Recently, chemical vapour deposited (CVD) single crystal diamond has become available, offering the opportunity to study the properties of this synthesised material independent of grain boundaries. This work focuses on particle induced charge pulses studied as a function of temperature between 200 K and 296 K in polycrystalline and single crystal material. Thermally activated re-emission of holes out of shallow trap levels is clearly observed in this temperature range. The electrical characterisation is complemented by other techniques, such as polarising microscopy and luminescence studies. Time resolved ion beam induced charge (IBIC) imaging on a single crystal was also performed. The charge collection efficiency of the devices hardly shows a temperature dependence in the investigated range, but polarisation and priming affect the detection performance. The pattern in the IBIC images of the single crystal reflects the spatial distribution of the luminescence signature of nitrogen impurities and dislocations, giving direct evidence of their degrading effect on the charge carrier mobility-lifetime product (μt). Additionally, there is some structure in the μt images evolving with the growth direction of the CVD material. The spatial distribution of internal electric fields will be discussed together with the effects of polarisation/priming processes. The recent progress in high purity single crystal synthesis of CVD diamond is a major step for its application as a radiation detector with spectroscopic properties. The study of these single crystals will improve the understanding of the relation between defects and the bulk charge transport properties of diamond.

Several groups have demonstrated the potential of the Pockels effect in Cadmium Zinc Telluride (CZT) as a means to detect ionizing radiation. Migrating charge carriers are believed to generate the signal detected via the Pockels effect due to the distortions they create within the electric field, however trapped space charge beneath the cathode has been regularly observed which suggests that the signal amplitude is potentially dominated by a large dose element. In this work, the effects of electric field collapse at the location of charge carrier generation, rather than where space charge builds up, is demonstrated. This confirms the potential to apply the technique for imaging dose rate distributions. Charged coupled device (CCD) images representing the changes in electric field within the crystal were taken and the response to illumination from a collimated 1550 nm 4.5 mW IR laser and irradiation from 150 kVp X-rays measured. The data demonstrates that the signal acquired is a combination of both the local change in the electric field at the location where the carriers are being released/generated and an element caused by them becoming trapped, leading to space charge near the cathode. Whilst the presence of both components has been demonstrated, their time response to an IR pulse measured via a photo-diode is the same (within the 6 ms time limitation of the system). This means that when using a Pockels detection system the average change in field can be considered proportional only to the incident dose rate when working in the millisecond regime. In addition to finding the origins of the detected signal an investigation into the effects of doping a Cadmium Manganese Telluride crystal with vanadium was carried out to see whether the large increases in Pockels constant found in the literature when using doped CZT could be replicated. However, it was found that whilst there is a slight improvement in the constant and hence the sensitivity of the crystals it was not as significant as hoped. A fibre optic Mach-Zehnder interferometer has also been designed and built with the aim of developing further the results from a previous free-space concept demonstrator. In its present condition the effects of environment have been minimised but the detector system struggles with large attenuation losses due to repeated coupling into fibres and is currently not usable, however, increasing the power of the laser and trying to limit even further the free-space elements in the future should remedy this.

Third generation synchrotron facilities such as the Diamond Light Source (DLS) have a wide range of experiments performed for a wide range of science fields. The DLS operates at energies up to 150 keV which introduces great challenges to radiation detector technology. This work focuses on the requirements that the detector technology faces for X-ray Absorption Fine Structure (XAFS) and powder diffraction experiments in I12 and I15 beam lines, respectively. A segmented HPGe demonstrator detector with in-built charge sensitive CUBE preamplifiers and a Schottky e- collection CdTe Medipix3RX detector systems were investigated to understand the underlying mechanisms that limit spectroscopic, imaging performances and stability and to find ways to overcome or minimise those limitations. The energy resolution and stability of the Ge demonstrator detector was found to have the required characteristics for XAFS measurements. Charge sharing was identified as a limiting factor to the resolution which is going to be addressed in the future development of a full detector system as well as reductions in electronic noise and cross-talk effects. The stability study of the Schottky CdTe Medipix3RX detector showed that polarization is highly dependent on temperature, irradiation duration and incoming flux. A new pixel behaviour called tri-phase (3-P) pixel was identified and a novel method for determining optimum operational conditions was developed. The use of the 3-P pixels as a criterion for depolarization resulted in a stable performance of the detector. Furthermore, the detector was applied in powder diffraction measurement at the I15 beam line and resulted in the detector diffraction pattern matching the simulated data. CdTe Medipix3RX and HEXITEC spectroscopic imaging detectors were applied in identification and discrimination of transitional metals for security application and K-edge subtraction for medical applications. The results showed that both detectors have potential to be applied in fields outside synchrotron radiation.

The halogen quench gas present within a Geiger-Müller detector will govern its operational lifetime. Such halogen gases are highly corrosive and are very likely to interact with their surroundings. This factor must be taken into account when designing GM detectors to extend their lifetimes. The quench gas depletion is thought to be linked to the current resulting from the gas ionisation from each detection event. As such, GM detector lifetimes are typically expressed in units of total counts accumulated. At elevated temperatures, the molecules will possess more thermal energy and become more likely to interact. To preserve the amount of halogen gas in each detector, three different corrosion-resistant techniques have been considered for investigation; the samples used are ZP1200 GM detectors that consist of 446 stainless steel components. The surface treatment techniques used to prepare each sample were labeled as “raw” for an oxygen plasma process, “passivated” for a combination of a nitric acid passivation and an oxygen plasma process and, finally, “plated” for a combination of a chromium plating process and an oxygen plasma process. The effectiveness of each process has been studied at temperatures of up to 175 oC. A Caesium-137 source was used to age all detector samples by irradiating them with dose rates of 1.3 mSv/hr. 32 samples were aged at room temperature and another 32 samples were aged in parallel at an elevated temperature of 125 oC. At room temperature, all detector types produced stable detectors with operational parameters that did not change significantly with age. The plated samples did show an initial rise in their starting voltage (Vs) measurements. At 125 oC, the plated detectors produced the most stable lifetime performance after an initial Vs conditioning period. The passivated and raw detector samples, however, showed a drop in their Vs values. Preliminary studies carried out at 175 oC confirm the superiority of the chromium plating process at resisting performance degradation at elevated temperatures. After investigating the surfaces of the detector components, no changes with age in the bromine content were observed. The plated cathodes showed no bromine deposits when investigated using Energy Dispersive X-Ray Spectroscopy. Bromine was detected on the passivated and raw cathode surfaces, but its quantity remained unchanged with age. The impact of contamination on the performance of gas-filled radiation detectors was also investigated in collaboration with the Institut Laue-Langevin in Grenoble, France.