Experimental and theoretical studies of a 35 GHz cyclotron autoresonance maser amplifier

Abstract

Experimental and theoretical studies of a cyclotron autoresonance maser (CARM) amplifier are reported. The measurements are carried out at a frequency of 35GHz using a mildly relativistic electron beam (1.5 MeV, 130A, 30 ns) generated by a field emission electron gun followed by an emittance selector that removes the outer, hot electrons. Perpendicular energy is imparted to the electrons by means of a short bifilar helical wiggler. The entire system is immersed in a uniform axial magnetic field of 6-8 kG. With an input power of 17 kW at 35 GHz from a magnetron driver, the saturated power output is 12 MW in the lowest TE 1 1 mode of a circular waveguide, corresponding to an electronic efficiency of 6.3%. The accompanying linear growth rate is 50 dB/m. When the system operates in the superradiant mode (in the absence of the magnetron driver) excitation of multiple waveguide modes is observed. A threedimensional simulation code that has been developed to investigate the self-consistent interaction of the copropagating electromagnetic waveguide mode and the relativistic electron beam is in good agreement with the experimental observations.

Proposed research on advanced accelerator concepts

“…It has been benchmarked against a linear kinetic theory [14], [15], and has been found in good agreement with recent CARM amplifier experiments [16].…”

“…Under the auspices of this grant, extensive theoretical and computation investigations have been carried out. These have included: (a) linear and nonlinear analysis of multimode interactions in CARM amplifiers [14], [15], (b) development of a three-dimensional self-consistent code for CARM amplifier and CRL accelerator simulations [5], [15], (c) detailed comparisons between theoretical predictions and experiments [16], and (d) studies of efficiency optimization [13].…”

Theory of electron-cyclotron-resonance laser accelerators

“…We refer this interaction as the inverse cyclotron autoresonance maser interaction, because the underlying equations of motion describing such an interaction are identical to those governing the cyclotron autoresonance maser (CARM) [12]- [16]. The scaling laws are verified.…”

Emission of solar radio spikes by beam-driven cyclotron resonance

“…When the working parameters are suitable, stimulated collective emissions can be emitted. The second is the beamdriven cyclotron resonance maser mechanism (Bratman et al, 1983;Pendergast et al, 1988;Kleva, Levush, and Sprangle, 1990;Di Rienzo et al, 1991) which requires only an axial magnetic field, which is a configuration common in space plasmas. The wiggler is self-generated by the gyromotion of the electron beam, which leads to gyrophase electron bunching.…”