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Components for the testing of a co-harmonic gyrotron cavity

Research output: Contribution to conference - Without ISBN/ISSN Conference paper

Published
  • D. A. Constable
  • Kevin Ronald
  • Wenlong He
  • Xenofon S. Fampris
  • Alan D. R. Phelps
  • Adrian W. Cross
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Publication date15/07/2010
Original languageEnglish
EventNational Vacuum Electronics Conference (NVEC) 2010 - Cockcroft Institute, Daresbury, United Kingdom
Duration: 14/07/201015/07/2010
http://indico.hep.manchester.ac.uk/conferenceDisplay.py?ovw=True&confId=2288

Conference

ConferenceNational Vacuum Electronics Conference (NVEC) 2010
Abbreviated titleNVEC
CountryUnited Kingdom
CityDaresbury
Period14/07/1015/07/10
Internet address

Abstract

A primary objective for the field of vacuum electronics is the development of
devices capable of generating coherent, high power radiation within the sub-mm
regime. The electron cyclotron maser instability offers an attractive method of
fulfilling such requirements, being a well established mechanism for obtaining
coherent, high power radiation within the mm-band. However, operation at high
harmonics of the electron cyclotron frequency, ωc, proves challenging, given the
sensitivity of parasitic modes to the large beam currents required.

Previously, particle-in-cell simulations have been presented on the
simultaneous operation of a gyrotron cavity at the 2nd and 4th harmonics of the
electron cyclotron frequency[1]. Such a co-harmonic scheme is used to obtain high frequency radiation through the direct excitation of a low harmonic signal. By then trapping the low harmonic within the interaction region, through the use of a cut-off aperture, pure output of the high harmonic signal can be realised. However, the intended output radiation is dominated by a mode converted 2nd harmonic signal.

Analysis of the setup suggests that such mode conversion occurs due to the cut-off aperture, and while the magnitude of the converted signal can be reduced, it cannot be eliminated entirely.

As a result, the current focus is to confirm the presence of this mode
conversion experimentally. To that end, the design and fabrication of several
additional components has been required. A brief overview of these components will be given, along with some initial experimental results