[en] A self-consistent, one-dimensional model of the cyclotron autoresonance maser (CARM) amplifier is developed, and numerical simulations based on this model are described. Detailed studies of the CARM gain and efficiency for a wide range of initial energy and velocity spreads are presented. The interaction efficiency is found to be substantially increased when the axial magnetic field is tapered. For example, efficiencies of greater than 41 percent are obtained for a 140-GHz CARM amplifier with a tapered axial magnetic field and a 700-kV 4.5-A electron beam with parallel velocity spreads of less than 1 percent. A discussion of the nonlinear bandwidth and interaction sensitivity to axial field inhomogeneities is presented

[en] In this paper high-power CARM and FEL research on a long-pulse (1 μs) high-voltage (700 kV) modulator at the MIT Plasma Fusion Center is described. The experimental results on a Ka-band, long-pulse CARM oscillator experiment are presented. In this experiment, a SLAC 5045 klystron gun produced an electron beam at 250-320 kV and 10-20 A; a beam α ≡ p perpendicular/p parallel, variable from 0 to 1, was produced on this electron beam with a wiggler magnetic field near guide field resonance. CARM operation was observed for many parameter settings, and for frequencies ranging from 29 to 32 GHz. Output powers as high as 110 kW were achieved with an efficiency of up to 1.8%. Higher frequency radiation at 74.5 GHz was also obtained and is attributed to second harmonic CARM operation. Recent operation of an FEL experiment using a 580 kV, 0.27 μP electron gun, built by Thomson Tubes Electroniques, and a permanent magnet helical wiggler with λ_w ± 3 cm and B_w = 500 G is described. Results include measurement of small signal gain, gain-bandwidth, and oscillation at 30 GHz, with power levels of approximately 1 MW

[en] Cyclotron autoresonance maser (CARM) amplifiers are under investigation as a possible source of high-power (> 100 MW), high-frequency (> 10 GHz) microwaves for powering the next generation of linear colliders. A design for a high-power, short pulse, 17.136 GHz CARM amplifier, utilizing a 500 kV linear induction accelerator, is presented

[en] The authors discuss two studies of cyclotron autoresonance maser (CARM) amplifiers underway at M.I.T. They differ both in frequency and in the technologies employed. The 35GHz amplifier uses a 1.5MeV,260A,30ns electron beam from a field emission (explosive) cathode energized by a Marx type, Physics International Pulserad accelerator. The entire system is immersed in a uniform, pulsed magnetic field 7kG. Measurements give a small signal gain of 90dB/m, a saturated power output of 10MW and an electronic efficiency of 3%. The 140GH_z amplifier under development will employ a 450-700kV, 30A, 1μs electron beam from a Pierce-type gun driven by a high-voltage, long-pulse modulator. The magnetic field (--25kG) in the CARM interaction region will be produced by a superconducting magnet. Theoretical investigations of CARM efficiency, efficiency enhancement by magnetic field tapering, and amplifier stability are also being carried out