A broadband gyrotron backward-wave oscillator with tapered interaction structure and magnetic field
Journal
Physics of Plasmas
Journal Volume
22
Journal Issue
11
Date Issued
2015
Author(s)
Li, G.D.
Chang, P.C.
Chen, H.Y.
Chiang, W.Y.
Fan, C.T.
Lin, P.N.
Kao, S.H.
Lin, Y.N.
Huang, Y.J.
Barnett, L.R.
Abstract
The gyro-monotron and gyrotron backward-wave oscillator (gyro-BWO) are the two oscillator versions of gyrotrons. While serving different functions, they are also radically different in the RF field formation mechanisms. The gyro-monotron RF field profile is essentially fixed by the resonant interaction structure, while the gyro-BWO possesses an extra degree of freedom in that the axial RF field profile is self-determined by the beam-wave interaction in a waveguide structure. The present study examines ways to utilize the latter feature for bandwidth broadening with a tapered magnetic field, while also employing a tapered waveguide to enhance the interaction efficiency. We begin with a mode competition analysis, which suggests the theoretical feasibility of broadband frequency tuning in single-mode operation. It is then shown in theory that, by controlling the RF field profile with an up- or down-tapered magnetic field, the gyro-BWO is capable of efficient operation with a much improved tunable bandwidth.
SDGs
Type
journal article