GaAs radiation detectors

[摘要] This thesis presents the results obtained with radiation detectors made with Schottky barrier contacts to GaAs. Three types of detectors are investigated, namely pads, microstrips and pixellated detectors on both semi-insulating un-doped material as well as on epitaxial material. Tests, devised and carried out by the author, which use a variety of radiation sources to characterise the devices are described. Read out electronics used in conjunction with these detectors are described as well as the tests performed in high energy particle beams at CERN, the European Centre for Nuclear Research. Irradiations of the detectors have also been carried out at CERN, in the Rutherford Laboratory and at a commercial site in France to measure the "radiation hardness" of these detectors. Their suitability for use in the High Energy Physics environment has not been proven due to the progress made in increasing the resistance of detectors made from silicon to the high radiation dose. Initial work on pixellated detectors for HEP applications has turned to the field of X- ray imaging as a natural alternative where GaAs has much to offer. Measurements have been done to evaluate the imaging capabilities of GaAs detectors using read out electronics developed for HEP. A 320 x 240 array of bump bonded pixels each 38 mum square has been tested using a charge integrating readout with results indicating a performance of better than 10 line pairs per mm. Epitaxially grown material has been investigated and shown to perform well as a detection medium. The purest material that has been tested still has a free carrier concentration that is at least an order of magnitude too high. An initial investigation into a novel photonic detector read out scheme is presented. The idea involves the use of reflective optical modulators to readout the charge from the detector element. A modulator was designed and successfully tested in order to demonstrate that this is possible. The integrated detector/modulator did not perform as hoped and alternative directions have been suggested.

[发布机构] University:University of Glasgow

[关键词] Nuclear engineering