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The Advanced GAmma Tracking Array, AGATA, is a European project aimed at constructing a next-generation gamma-ray spectrometer for nuclear structure studies. The completed array will consist of a 47f shell of 180 highly segmented HPGe detectors arranged into 60 triple clusters. The array will be instrumented with state of the art digital electronics, and will apply Pulse Shape Analysis (PSA) and Gamma-Ray Tracking (GRT) algorithms to achieve high efficiency while maintaining the excellent peak-to-total ratio of current escape-suppressed spectrometers. Vital to the successful application of PSA is the establishment of a pulse shape database describing the signal shape produced by interactions at each point in the detectors volume. Electric field simulations have been developed within the AGATA collaboration to provide this signal basis but it is necessary that they are tested against experimental measurements. Characterisation measurements were performed on asymmetric AGATA capsule C00l using the Liverpool scanning system and state-of-the-art digital electronics. A highly collimated beam of 662ke V gamma rays was scanned across the detector and single and coincident trigger modes were used to measure the response due to gamma rays interacting at precisely determined points within the detector. These signals were then compared with signals produced by the electric field simulations Multi Geometry Simulation (MGS) and JAVA AGATA Signal Simulation (JASS) and an assessment made of their performance. Position resolutions of 7.8mm and 8.4mm have been measured when performing PSA with MGS and JASS respectively. These values are larger than expected and an attempt has been made to understand the reasons for this. In addition, measurements have been carried out to assess the electronics response function of the detector and associated electronics. The results of these characterisation measurements will be used by the AGATA collaboaration to refine the online PSA and GRT algorithms used with the array.

CdZnTe has been the focus of intense research as an attractive alternative material as a semiconductor radiation detector. Due to recent advances in the growth of the CdZnTe crystals it has been possible to develop small pixel, spectroscopic radiation detectors which overcome the poor hole transport properties of CdZnTe. This project utilized the PIXIE ASIC to investigate effects relating to pixelated detectors. This work focused a wide range of effects relating to pixelated CdZnTe radiation detectors. Investigations into single pixel effects resulted in investigation how different components of electronic noise effect detector performance. Furthermore the charge collection efficiency of each pixel was investigated to quantify its effect on the spectroscopic performance. Multiple pixel effects, for example charge sharing between adjacent pixels when pixel size is significantly smaller that detector thickness was investigated. X-ray spectroscopy studies were undertaken to investigate how the level of charge sharing is effected by the incident X-ray energy and the pixel size of the pixel array. Charge sharing and charge loss in a 250 Mm pitch CdZnTe pixel detector was also investigated using a mono-chromatic X-ray beam at the Diamond Light Source, U.K. Using a 20 Mm beam diameter the detector response has been mapped for X-ray energies both above (40 keV) and below (26 keV) the material K -shell absorption energies to study charge sharing and the role of fluorescence X-rays in these events. Furthermore how the bias applied to detector effects the level of charge sharing and charge loss will be investigated.

A small, battery-powered ultraviolet radiation detector was developed using three spectrally distinct photodiodes housed in a weatherproof enclosure (cylinder with r=16mm, h=15mm) under an acrylic window. Each induced photocurrent (plus a temperature reading) was amplified and conditioned electronically, converted to a digital number and stored in a non-volatile memory space, contained in another small enclosure (cuboid, 100x70x30mm). Each reading was time-stamped. The detector was characterised in the laboratory to determine its spectral sensitivity, angular response, linear response, temperature dependency and dark current. It was calibrated in natural sunlight, at a range of solar zenith angles, ozone column amounts and cloud conditions, against a Bentham DTM300 spectroradiometer. The results showed it to approximate the irradiance weighted by four distinct biological action spectra with an overall accuracy of 20%. It was tested in a number of field settings and shown to operate in a range of environmental conditions and provide data that had scientific relevance. A number of the detectors were used in two personal dosimetry experiments. The data revealed distinct exposure patterns between occupational and recreational days, and highlighted the strong influence of behavior on both ultraviolet exposure rates and integrated doses. Further, it was shown that the relative balance of previtamin D photosynthesis and erythemally weighted irradiance is not dependent on solar zenith angle when one considers a population with varying behaviors in a variable climate.

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Nowadays, there has been an increasing interest in Terahertz (THz) radiation for application across scientific disciplines including atmospheric sensing, medical diagnosis, security screening and explosive detection. The limitation of THz generators and detectors has gained interest from scientists and engineers to explore the development of both sources and detectors. With the advantages of low cost, low power consumption, high reliability and potential for large-scale integration, sub-THz generator and detector can be developed using CMOS process technology. In this thesis, an IMPATT diode acts as a sub-THz generator, HEMTs and MOSFETs act as sub-THz detectors, which are developed in AMS 0.35 μm CMOS technology and UMC, 0.18 μm CMOS technology. The size of the IMPATT diode was 120 μm x 50 μm with the target resonant frequency at 30 GHz. The experiment results show that the operating frequency of the IMPATT diode was between 12 GHz up to 14 GHz. Then by using HEMTs with 0.2 μm gate length and 200 μm gate widths, sub-THz radiation detection has been demonstrated. Experimental results show that the photoresponse depends on the drain current and the gate to source voltage VGS. In addition, photoresponse also depends on varying frequencies up to 220 GHz and fixed the drain current. Furthermore, the HEMT also give an indication of response by varying the input power of microwave extender. MOSFETs from two types of CMOS technology; AMS 0.35μm and UMC 0.18 μm technology with different gate length ranging from 180 nm up 350 nm were demonstrated. These results provide evidence that the photoresponse increases with the drain current and the RF input power, but inversely to the frequencies. These results also provide evidence that the MOSFETs are able to work as low cost and sensitive sub-THz detector.

A study of the decayτ → π⁻ π⁻ π⁺ π⁰ π⁰ ν(τ) is presented. The results presented here could be used to inform and improve the Monte Carlo simulations.