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

Lead Research Organisation: Queen Mary, University of London
Department Name: Sch of Electronic Eng & Computer Science

Abstract

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.

Publications

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Bowes D (2014) X-ray emission as a diagnostic from pseudospark-sourced electron beams in Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms

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Bowes D (2014) Visualization of a Pseudospark-Sourced Electron Beam in IEEE Transactions on Plasma Science

 
Description To achieve higher BWO output power levels in the hundreds of GHz to THz range, a higher current density electron beam, around the 100s of A/cm2, is required. But as the frequency is increased towards the THz range, the diameter of the BWO interaction region has to be reduced in order to prevent the beam-wave interaction region becoming overmoded which results in a loss of the temporal or spatial coherence of the output radiation. To satisfy the beam requirements for THz devices, the pseudospark-sourced electron beam was used due to it possessing the highest combined beam density and brightness as compared to any other electron beam source. Because of its high current emission and special discharge characteristics it has many useful potential applications such as an electron beam driven X-ray source, THz remote imaging and plasma diagnostics.
Exploitation Route The pseudospark source has attracted significant world wide interest due to its ability to generate THz radiation without the need to use an axial guide magnetic field.
Sectors Education,Electronics,Healthcare,Manufacturing, including Industrial Biotechology

 
Description A pseudospark discharge to generate a sub-mm diameter electron beam that does not require an external magnetic field to drive a high frequency millimetre wave source has been achieved. It was demonstrated that the initial high-energy electrons generated by the pseudospark discharge ionises the background gas to form a plasma channel, the electron beam subsequently generated by the PS discharge then propagates along the plasma channel. The research output from this project has been excellent, as witnessed by the substantial number of publications in journals and also the dissemination of the research has been strongly promoted by publication in research conferences. The pseudospark research was selected for five invited talks {(ICTP Trieste, Italy, 2009), (MIT, Boston USA, 2010) and (VEDA-2012 CSIR-CEERI, Pilani, Rajasthan, India, 2012)}, International Conference on Plasma Science, Technology and Applications (ICPSTA-2016), Amity School of Applied Sciences, Amity University Uttar Pradesh (AUUP), Lucknow campus, India.
First Year Of Impact 2009
Sector Education,Electronics,Healthcare,Manufacturing, including Industrial Biotechology
Impact Types Economic

 
Description Adrian Cross 
Organisation University of Strathclyde
Country United Kingdom 
Sector Academic/University 
PI Contribution My group carried out some modelling of the pseudospark discharge using the Particle In Cell code MAGIC
Collaborator Contribution Prof Cross' group conducted an extensive experimental work
Impact 6 joint papers
Start Year 2010