Constable, D. A. and Ronald, Kevin and He, Wenlong and Fampris, Xenofon S. and Phelps, Alan D. R. and Cross, Adrian W. (2010) Components for the testing of a co-harmonic gyrotron cavity. In: National Vacuum Electronics Conference (NVEC) 2010, 2010-07-14 - 2010-07-15, Cockcroft Institute.
Full text not available from this repository.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