SHeet Electron beam vacuum eLectronic Devices for the generation of hIGH power THz radiation

Lead Research Organisation: University of Strathclyde
Department Name: Physics


THz frequency (300GHz to 1THz) radiation sources are used in a number of diverse applications such as radars, the study of the fundamental properties of materials, security imaging, magnetic resonance spectroscopy, plasma diagnostics, medical imaging and chemical sensing. The power that can be generated from 'bench top' 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 size of the interaction region has to be reduced in order to prevent the maser becoming overmoded which results in a loss of the temporal or spatial coherence of the output radiation. As the frequency increases it becomes increasingly difficult (if not impossible) using conventional thermionic cathodes to focus and form high current density, high quality electron beams through the small size interaction region of the THz maser. A pseudospark plasma cathode can overcome current density limitations imposed by thermionic emission as well as being able to generate a sheet electron beam without the need to use an external magnetic field.

A psuedospark-sourced sheet electron beam will be used to power a planar Extended Interaction Klystron Amplifier (EIKA) which is extended in one direction as compared to conventional EIKAs based on a cylindrical electron beam produced by a thermionic cathode. A 12mW, 365GHz signal generated by a solid state source will amplified to 100W by the Pseudospark Sheet beam planar Extended Interaction Klystron Amplifier (PS-EIKA). As no guide magnetic field is required the PS-EIKA will be compact, reliable, robust and can generate 100ns duration pulses at high (kHz) pulse repetition frequencies. In addition a pseudospark source sheet electron beam will be used to drive a planar Extended Interaction Oscillator (EIKO) to generate 10W of output power at 1THz. The proposed research will be conducted jointly by two leading research groups in microwave device engineering with complementary expertise, in Univ. of Strathclyde and QMUL.

Knowledge of pseudospark Extended Interaction Klystron amplifier (PS-EIKA) and oscillator design and construction will be transferred to our Project Partner. A community network of THz amplifier users in magnetic resonance spectroscopy, plasma diagnostics and mm-wave radar applications will be built up to the benefit of future co-created research collaborations. These include the use of the PS-EIKA in Electron Paramagnetic Resonance (EPR) and to improve the sensitivity by many orders of magnitude of Nuclear Magnetic Resonance (NMR) through DNP techniques. The EPR and DNP enhanced NMR (including the possibility of pulsed DNP-NMR and the use of phase and amplitude modulation) experiments will strongly enhance the UK's position as a world leader in a wide range of academic research areas in physics, chemistry, biology, engineering and medicine. These sources are also of national and international importance in the areas of magnetically confined fusion for plasma diagnostics and mm-wave radar systems.

New high power sub-millimetre wave amplifiers and terahertz oscillators will be constructed for radically improved sensitivities in NMR/DNP and EPR instruments in high magnetic fields, enhanced plasma diagnostics and THz imaging. Network activities as part of the proposal will bring together leading groups/industries in the magnetic resonance spectroscopy, microwave plasma diagnostics community and the high power amplifier and microwave/mm-wave source community. Increased capability in these areas as well as enhanced capability to measure fast and slow moving objects using sub-millimetre wave radars will be exploited via our Project Partner. All network members have an outstanding track record in relevant technology and methodology development and all have strong links with National and International applications programs with multiple collaborators across RF and Microwave science and technology application areas.

Planned Impact

We believe the proposal has the potential to create impact on an academic, societal and economic level as well as consolidating developing the careers of the researchers in the field of novel amplifiers and oscillators in the sub-millimetre wave and THz band.

The Extended Interaction Klystron Amplifier and Extended Interaction Klystron Oscillator is a technology with potential for high societal impact on a large number of themes, with strong public recognition, such as 1) well-being and longevity of society: through its high sensitivity NMR as methods of biomarkers, imaging and medicine discovery for large numbers of diseases including cancers; 2) high power amplifiers and oscillators for high resolution radar imaging of invading flying objects, 3) security and safety of society: real time security imaging (through clothes and bags) for contrabands such as explosives, illegal drugs,; 4) THz sources for new spectroscopic material measurement technique; 5) understanding of a critical phenomenon such as the anomalous transport of the plasma in fusion energy sources.

A confidential market review highlighted demand and tremendous interest from key opinion leaders in DNP, EPR and a major global instrumentation business showing a demand of up to 50 sub-millimetre wave amplifier systems each year, hence a multi-million pounds per annum high value business proposition. It has huge economic impacts through our links with TMD Ltd, (switched mode power supply manufacturers and vacuum tube manufacturers) who have links to Thomas Keating Ltd (spectrometer and EPR instrumentation) and through academic colleagues in the fields of chemical and biological science. There are also important, significant applications for these terahertz amplifiers in security, radar and material characterisation which will be exploited by our project partner TMD Ltd.


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Description Models have been developed to indicate a pseudospark discharge can generate a sheet-electron beam to drive a planar Extended Interaction Klystron to produce high power (kW) sub-millimetre (395GHz) wave radiation without the need to use an applied magnetic field. An sub-millimetre wave (395GHz) Extended interaction Oscillator has been designed an is presently under construction. A sheet electron beam produced by a PS-discharge has been measured.
Exploitation Route In vacuum electronic devices, high quality intense electron beams are essential as the frequency increases, thus the pseudospark (PS) discharge has attracted a lot of attention recently as a promising source of high quality, high intensity electron beam pulses with the beam current density up to 108 A m-2 and brightness up to 1012 A m-2 rad-2. This is because a PS-sourced electron beam has the ability to self-focus due to the unique discharge structure and the formation of an ion channel generated by the beam front. This beam has a higher combined current density and brightness compared to electron beams formed from any other known type of electron source and makes it an excellent electron beam source for desirable compact millimetre wave devices. PS-sourced electron beams have been applied in many fields such as material processing, free electron lasers, x-ray sources, extreme-ultraviolet production, and microwave devices.
Sectors Aerospace, Defence and Marine,Agriculture, Food and Drink,Digital/Communication/Information Technologies (including Software)

Description Yes the pseudospark research has been used by scientist based a CSR-CEERI India and its emerging applications as high power plasma switch (PSS); high density and energetic electron beam sources for potential microwave applications; and EUV/X-ray generation.
First Year Of Impact 2020
Sector Agriculture, Food and Drink,Digital/Communication/Information Technologies (including Software),Environment,Manufacturing, including Industrial Biotechology
Impact Types Societal,Economic

Description SHeet Electron beam vacuum eLectronic Devices for the generation of hIGH power THz radiation
Amount £598,368 (GBP)
Funding ID EP/S00968X/1 
Organisation Engineering and Physical Sciences Research Council (EPSRC) 
Sector Public
Country United Kingdom
Start 08/2018 
End 08/2020
Title XOPIC sheet beam plasma modellng 
Description XOPIC sheet beam plasma model has been developed at the University of strathclyde 
Type Of Material Computer model/algorithm 
Year Produced 2020 
Provided To Others? No  
Impact XOPIC model of the pseudospark sourced sheet electron beam is being developed at the University of Strathclyde and the putpur results are in the process of being published 
Description Collaboration with Prof Xiaodong Chen on pseudospark modelling at Queen Mary University London (QMUL), UK 
Organisation Queen Mary University of London
Department School of Electronic Engineering and Computer Science
Country United Kingdom 
Sector Academic/University 
PI Contribution Prof Chen's group is carrying out modelling of the pseudospark discharge using the Particle In Cell codes. This complements the modelling of the pseudospark electron beam in the background plasma and experiments carried out at Strathclyde.
Collaborator Contribution The QMUL group are modelling the initiation of the PS discharge.
Impact Outputs were in the form of 5 joint University of Strathclyde and QMUL refereed journal papers.
Start Year 2012
Description Raman research fellowship, Dr. Udit N. Pal 
Organisation Council of Scientific and Industrial Research
Country India 
Sector Public 
PI Contribution I supported a Raman Fellowship application of Dr. Udit N. Pal for a 4 month (15th July 2020 to 15th November 2020) collaborative research visit to the ABP group, department of Physics, University of Strathclyde to carry out joint pseudospark discharge experiments to produce highly energetic and stable electron beams for the development of portable and tunable EUV/Soft X-ray sources. Dr. Udit N. Pal was awarded one of twelve Raman Fellowships awarded across the whole of Council of Scientific and Industrial Research (CSIR), India consisting of 38 laboratories/institutes, 39 outreach centres, 3 Innovation Centres with a collective staff of over 14,000,
Collaborator Contribution Dr. Udit N. Pal has made an outstanding research contribution to the design and development of pseudospark discharge based high power plasma switches and electron beam sources and has extensive knowledge and experience of Xe filled Dielectric Barrier Discharge sources for efficient VUV/UV generation. He has successfully executed, contributed and completed a number of pseudospark research projects publishing his results in many excellent high quality peer reviewed journals. We plan to conduct joint pseudospark sheet electron beam experiments in the Atoms, Beams and Plasma group, University of Strathclyde in the summer of 2020.
Impact Outputs are expected at the end of 2020 after Dr. Udit N. Pal has completed his collaborative Raman Research Fellowship visit to the ABP group, Physics, university of Strathclyde, from the 15th of July 2020 to the 15th of November 2020
Start Year 2019
Description National Vacuum Electronics Conference (NVEC) 2019 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach Local
Primary Audience Postgraduate students
Results and Impact Results from the sheet electron beam pseudospark project was presented at the National Vacuum Electronics Conference 2019 held in the Technology and innovation Centre, University of Strathclyde on the 13th of November 2019
Year(s) Of Engagement Activity 2019