25 July 1989 Intense Electron Beam Cyclotron Masers With Microsecond Pulselengths
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Experiments are underway to investigate the generation of MW to GW microwave power levels utilizing intense (1-10 kA), relativistic (0.4-1 MV), electron beams with pulselengths from 0.4 to 1 μs. Significant research issues concern the effects of beam voltage fluctuations and space charge on long-pulse microwave emission power and frequency stability. Two prototype masers have been developed utilizing a moderate energy pulseline generator with peak parameters: 0.4 MV, 1.2 kA, and 0.4 μs. Prototype I utilized a nonadiabatic step in the diode magnetic field to impart a large α (V⊥/V11≈1-2) to a relatively low transported current of 30-60A. With a uniform waveguide resonator this maser generated peak microwave power levels of 0.6 MW and pulselengths of 0.3 μs over 85% voltage droop. The emission frequency was close to the relativistic cyclotron frequency. The Prototype II maser employed an improved magnetic field profile which transported 500-1000 A of beam current, but at a lower value of α(0.2 - 0.3). A series of permanent magnet wiggler/kickers were used in preliminary tests. Power levels were achieved in the range of 2 MW in the X-band and at MW levels in the K-band. These emission frequencies apparently correspond to the CRM forward-wave and backward-wave interaction with the TE11n cavity modes. By lowering the magnetic field below a critical value the microwave emission was cut off. Design studies have been performed for a long-pulse MW-GW cyclotron maser on the MELBA accelerator with parameters: 0.8 - 1 MV, 1 - 10 kA, and 1 - 1.5 μs.
© (1989) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
R. M. Gilgenbach, R. M. Gilgenbach, J. G. Wang, J. G. Wang, J. J. Choi, J. J. Choi, C. A. Outten, C. A. Outten, T. Spencer, T. Spencer, } "Intense Electron Beam Cyclotron Masers With Microsecond Pulselengths", Proc. SPIE 1061, Microwave and Particle Beam Sources and Directed Energy Concepts, (25 July 1989); doi: 10.1117/12.951801; https://doi.org/10.1117/12.951801

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