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This thesis details the study of N~Z~28 nuclei obtained using the fusion evaporation reactions 19Ne +40Ca at a beam energy of 70 MeV and 24Mg-40Ca at a beam energy of 65 MeV. The 19Ne data constitute the first tests of a neutron-deficient Radioactive Ion Beam (RIB) for high-spin nuclear spectroscopy. The radioactive Ne beam was supplied by the coupled cyclotrons at the Louvain-la-Neuve facility, Belgium. Emitted gamma-rays were detected by an array of 7 TESSA-style Ge-detectors in the backward hemisphere in two rings. A degree of channel selection was also allowed by identifying evaporated charged particles with an array of 128 silicon-strip detectors (LEDA array). Background subtraction of radiation from the decay of the beam was achieved using the timing properties of the pulsed beam and through particle detection using the LEDA charged particle array Information on the relative evaporation residue cross-sections was obtained and the problems associated with performing such experiments in a high radioactive background environment are addressed. New information on the high spin states of 58Ni was obtained using the reaction 40Ca (24Mg, alpha2p), performed at the ATLAS facility at Argonne National Laboratory. Emitted 7-rays were detected by high efficiency AYEBALL array which consisted of 18 EUROGAM and TESSA-style Compton suppressed Ge-detectors in four annular rings. Channel selection is demonstrated by use of (a) mass selection using the Argonne Fragment Mass Analyser (FMA), (b) a split anode ionization chamber at the back of the FMA, and (c) an array of 11 neutron detectors in a ring at forward angles. The effectiveness of using recoil-gated gamma coincidence data for the study of nuclear structure in neutron-deficient nuclei close to the proton drip-line is shown. The excited states of 58Ni are compared with OXBASH shell model calculations and the problems associated with forming high angular momentum states in the limited valence space are addressed.

In this study the energy and mass dependences of the carrier removal cross section for high energy (0.25-2.0 MeV) light ion (H[+], D[+] and He[+]) irradiation of n-type GaAs are investigated. The materials used were of two types: (i) semi-insulating bulk GaAs and (ii) Vapour Phase Epitaxially (VPE) grown n-type GaAs on Semi-insulating substrate. The bulk material was implanted with Se[+], Zn[+] and Cd[+] ions at 390-400 keV and annealed (700° and 900°C) to create a thin (0.5 um) n- and p-type conductive layers, with carrier concentrations of 1 to 7x10[17] cm[-3]. The carrier concentrations for the Epitaxial materials were between 2.1x10[15] to 3.2x10[17] cm[-3]. The irradiations were carried out using the Van de Graaff accelerators at the University of Surrey and at AERE, Harwell. The ion doses were between 1x10[10] to 5x10[13] cm[-2]. The materials were irradiated at room temperature and at 8° off the normal to the surface. The measurement techniques used were "insitu" sheet conductivity and also Hall effect measurements. From the rates of change of the sheet conductivity and carrier concentration with the ion dose, values for the carrier removal rate (CRR) and carrier removal cross section (sigma[CR]) were calculated. These cross sections were compared to the elastic displacement cross section derived using Kinchin and Pease [116] theoretical model (sigma[KP]). It was found that the energy dependence of the cross section agrees with the theoretical prediction, but the mass dependence, at energies below 500 keV, was found to diverge from the theoretical mass dependence. Molecular ions (H[2+] and H[3+]) were found to dissociate upon impact with the surface of the target, with the resulting particles behaving similarly to Protons. The carrier removal rate was found to depend on the initial carrier concentration of the irradiated material, which is attributed to the movement of the Fermi level through the shallowest defect level reported (E1=E[c]-0.12 eV). From this dependence, values for defect introduction rates (DIR) for this level and for other deeper levels were estimated . The comparison of the DIR for different ions, showed that Deuterons and Protons followed the isotopic mass dependence, where as Helium differed. The surface layers of some samples were doped with Deuterons and it was demonstrated that the presence of the Deuterons has little effect upon the carrier removal cross section during 1.5 MeV Proton irradiation.

The development of a replacement to the conventional film based X-ray imaging technique is required for many reasons. One possible route for this is the use of a large area film of a suitable semiconductor overlaid on an amorphous silicon readout array. A suitable semiconductor exists in cadmium telluride and its tertiary alloy cadmium zinc telluride. In this thesis the spectroscopic characteristics of commercially available CZT X- and gamma-radiation detectors are established. The electronic, optical, electro-optic, structural and compositional properties of these detectors are then investigated. The attained data is used to infer a greater understanding for the carrier transport in a CZT radiation detector following the interaction of a high energy photon. Following this a method used to fabricate large area films of CdTe on a commercial scale is described. This is cathodic electrodeposition from an aqueous electrolyte. The theory and experimental arrangement for this technique are described in detail with preliminary results from the fabricated films presented. Attention is then turned to the CdS/CdTe films that are produced commercially for the photovoltaic industry. In this case the crystalline nature, surface topography and optical properties are investigated. A conclusion examines the progress that has been made towards the development of a large area flat panel digital imaging technique.

The distribution of 75Se in tissue equivalent materials was investigated employing Gamma ray Emission Tomography with a rectilinear scanner utilizing NaI(Tl) and BGO detectors. The reconstructed images, using Filtered Back Projection and Iterative techniques were presented in 2D colour and 3D representations. Using a lead collimator of aperture 1.5x20 mm and 70 length, the distribution of selenium with variation of volume and concentration was examined and clearly seen. Several corrections such as background, scattering, attenuation compensation and X-ray characteristic suppression, were performed to improve the quality of the images which was evaluated in terms of the fidelity factor. The possibility of quantifying an image was considered with regard to spatial resolution and least detectable concentration. The spatial resolution was measured using two small vials containing the same concentration of selenium, the value obtained was the same as the width of the collimator aperture. The value of the least detectable concentration of selenium however, was difficult to find, due to the many ambiguous factors involved. The binding site of selenium which is based on quadrupole interaction with the surrounding electric field, was investigated employing Perturbed Angular Correlation (PAC) experiments using NaI(Tl) and BaF2 detectors. Using NaI(Tl) detectors, it was difficult to observe the perturbation, due to the poor time resolution. The BaF2 detector according to the literatures has a shorter light emission decay time constant (0.6 ns), suggested that a better time resolution than that found with the NaI(Tl) detectors could be obtained. A Perturbed Angular Correlation experiment employing BaF2 detectors and a fast-slow coincidence system was set up. The time differential PAC of selenium in solution showed an unperturbed angular correlation pattern. The main problem is the very short half life of the intermediate state of 75Se (0.3 ns), making it difficult to observe the perturbation effect. The time resolution of the system (5.4 ns) will need to be improved by an order of magnitude or more for the investigations to continue.

The ternary compound Cadmium Zinc Telluride (CdZnTe) is one of the most promising room-temperature semiconductor detectors. It possesses the necessary material properties that are required to exhibit optimal detection performance. But unfortunately it does not display that expected level of performance because it has some shortcomings at various stages from crystal growth to contact fabrication. Investigations in each area have been pursued individually over the last decades and it is a goal in the field to integrate the optimal properties from each area into a fully optimised detector. In this work, the metal contacts to CdZnTe detectors have been investigated since these are believed to be one of the most vital areas among the possible detrimental aspects. In order to evaluate the contact features, different configurations of contact were fabricated on the supplied CdZnTe detector crystals using the available laboratory facilities. A great deal of effort was put into contact design and fabrication as well as the characterisation of the fabricated devices. Endeavour was made to correlate the characterisation results of different configurations with their physical structure as well as drawing comparison with commercial devices. Work was concluded by focussing on optimum detector designs including the factors that limit their performance.

Since the construction of the first commercial scanner for routine medical diagnosis implementing the principles of computerised tomography by Hounsfield in 1973 and its worldwide adoption, the use of various types of ionising and non-ionising radiations for tomographic imaging and other applications has been under continuous study. In this work a neutron beam has been used as the probe in order to obtain tomographic images, in transmission and emission modes, of the internal structure and elemental composition of test objects respectively. Various methods of neutron transmission tomography were studied and developed. A collimated He-3 proportional counter, a conventional combination of film/Gd-converter in a single cassette and a 35inm camera were employed as the detecting systems. A computerised video camera-based microdensitometer was used to digitise the radiographs obtained and a method to improve image noise was developed and tested. The technique of computerised tomography has also been applied to image elemental distributions, in the section of interest, employing delayed gamma-rays emitted by the object following neutron irradiation. The technique is not suitable in the case when very long-lived, very short-lived or stable isotopes are produced therefore a technique novel employing prompt gamma-rays emitted by the object during irradiation was developed and tested in this work. This technique has been termed Neutron Capture Prompt Gamma-ray Emission Tomography.

Data from the TASSO experiment at the PETRA e⁺e^- storage ring has been analysed to investigate the cross section for the QED reactions (a)e⁺e^- → e⁺e^- Bhabha scattering and (b)e⁺e^- → e⁺e^- + γ. Details of the TASSO detector and a detailed description of an array of lead/scintillator sandwich electromagnetic shower counters, used in the analysis of reaction (b), is given. For beam energies greater than 10 Gev the ratio of the measured total Bhabha scattering cross section to the QED prediction was found to be 0.949 ±0.013 (statistical) ±0.06(systematic). It was shown, by fitting the measured angular cross section, that QED is a point like theory down to distances of 2x10^-18 m. The predictions of models of electroweak unification have been compared to the data and parameters of these theories have been found to agree with, but not strongly constrain, these theories. Significant limits are placed on electroweak theories which predict more than 1 neutral weak gauge boson. The number of events with two charged tracks and one photon has been measured and compared to the QED cross section predictions for reaction (b). 21 such events were selected and this agrees well with the predicted number of 25±2.6. The agreement of these numbers has been used to determine that the mass of an excited electron state, e*, (which would contribute events to this experimental signature by its radiative decay) must be greater than 34 Gev (95% confidence limit), if it has normal couplings.

Trace elements within biological tissues are heterogeneously distributed. This complicates the task of deriving concentrations that represent an organ or specimen as a whole. The derivation of representative concentrations is important in the investigation of tissue health status or exposure to the individual from occupational or man-made pollution sources. Therefore, a knowledge of the elemental dispersions in biological tissues is required. Proton induced X-ray emission (PIXE) analysis is employed in the study of the elemental heterogeneity of porcine liver, kidney, heart and lung. Specimens are analysed in two different modes. One method involves the extraction of sub-samples that are dried, homogenised and manufactured into thick target pellets. This approach however limits the spatial resolution on which elemental distributions may be derived and hence thick specimen sections that can be irradiated directly may be preferred. This type of target though suffers in that surfaces are irregular and proton irradiation and X-ray take-off angles are ill defined. The effect of these surface imperfections upon X-ray yield in PIXE are investigated by the development of simple stylised models. The physical parameters of these models are varied and the elements most affected and dominant factors in modifying X-ray yield are identified. The trace element content for like tissues between targets in the form of pellets and freeze-dried sections are compared and mostly excellent correlation is found. The analysis of specimens in either of these modes stresses the high elemental inhomogeneity of biological samples. A quantitative determination of this elemental heterogeneity is made by the derivation of sampling factors, the minimum mass of material required to reduce elemental variations to a given level of precision. Those sampling factors derived by utilising the data from pelletised targets agree well with the limited values from the literature, whereas a large difference is found for those calculated from thick specimen target sections. This disagreement is thought to be due to the failure of sampling factor theory at the small sampling mass employed in the analysis of the latter targets. Photon transmission tomography was investigated for the ability of the technique to provide a measure of biological specimen heterogeneity, differentiate between different composite tissues and identify regions of interest. This may prove useful for the selection of sub-samples for subsequent trace element analysis. Biological specimens were scanned in fresh and dry states to ascertain the most favourable sample preparation technique to best achieve the above aims, the dry sample states were preferred. Freeze-dried specimens are imaged under differing scanning parameters and their data compared to theoretical values derived from PIXE and Rutherford backscattering (RBS) analysis. Good agreement is found. Regions of interest may be identified in tomographs, this being due to density variations rather than elemental variations, tissues of similar but different composition not being differentiatable due to image noise which is a product of finite counts in reconstructed images. However, with the improvement of photon counting statistics in images, these tissues may be more discernible from one another in tomographs thus making photon transmission tomography a viable technique for the selection of representative sub-samples for subsequent elemental analysis.