Generation of high power, high frequency radiation using high brightness pseudospark-sourced relativistic electron beams

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The principle aim is the investigation of the pseudospark discharge resulting in the generation of electron beam pulses with the highest simultaneous current density and brightness of any known type of electron beam source. Having constructed and operated the first coherent radiation source based on a pseudospark discharge, we have recently measured a high current density (1.5kAcm [-2]) electron beam of brightness 10[11] to 10[12] Am[-2]rad[-2], the proposed programme aims to enhance our understanding of the physics the pseudospark discharge as the size of this plasma cathode is reduced and to produce and transport for the first time small (mm and sub-mm) diameter electron pulses of exceptionally current density and beam quality. The power that can be generated from free electron radiation sources in the hundreds of GHz to THz frequency range has been limited by the fact that as the frequency is increased, the diameter of the interaction has to be reduced in order to prevent the maser becoming overmoded resulting in a loss of the temporal and spatial coherence of the output radiation. The reduction in the size of the interaction region makes it increasingly difficult (if not impossible) using conventional cathodes to focus and form high current density, high quality electron beams through the small size interaction region of a high frequency maser. It is our intention to combine the collective knowledge and expertise of three leading university research groups in the fields of 1) pseudospark physics, 2) computational modelling of millimetre wave sources and design of THz components and 3) advanced millimetre wave manufacturing technologies, to investigate the use of pseudospark sourced electron beam pulses to generate high power, high frequency coherent electromagnetic radiation via the klystron (200GHz) and backward wave (390GHz up to 1THz) instability.