High-Q Bragg resonator CARM experiments on a long-pulse electron beam accelerator

J. J. Choi

doi:10.1117/12.2301431

1 December 1990 High-Q Bragg resonator CARM experiments on a long-pulse electron beam accelerator

J. J. Choi

Proceedings Volume 1514, 15th International Conference on Infrared and Millimeter Waves; 15140L (1990) https://doi.org/10.1117/12.2301431
Event: 15th International Conference on Infrared and Millimeter Waves, 1990, Orlando, FL, United States

Abstract

Experimental measurements of high power microwave generation from an electron beam passing through a high-Q Bragg resonator have been performed using the long-pulse accelerator, MELBA. We have fabricated a high-Q sinusoidal Bragg resonator to study a high frequency CARM oscillator designed for operation on the TE₃₁ mode at 18.9 GHz and the TE4 1 mode at 20.5 GHz. A diffraction Q ~ 16,600 is consistent with the prediction of uncoupled single mode theory. A high quality annular electron beam of 30 - 80 amps is produced through 80 small holes in an apcrtured-mask-anode. The beam velocity ratio, α = ..., was directly measured by Cerenkov emission and radiation darkening on a glass plate diagnostic and agreed with calculations from Busch's theorem and an electron trajectory code. In preliminary results with the Bragg resonator, the peak full band (f < 14 GHz) power was in the range (0.6 - 1.2 MW); in the frequency band from 18.7 - 19.2 GHz (includes the TE₃₁ Bragg mode) the power was 15 dB less. Without the Bragg resonator (smooth tube) the peak full band power was 0.1 - 0.3 MW; the peak power in the band from 18.7 - 19.2 GHz was approximately equal to the full band power. Mode identification studies are underway, as fundamental and harmonic gyrotron interactions are believed to be a strong source of mode competition in the present experiments. Efficient, multi-megawatt microwave emission in the band 2.1 - 6.6 GHz is believed to originate from a TE₁₁-fundamental-mode gyrotron backward-wave-oscillation (gyro-BWO) in the Bragg resonator case.

Citation Download Citation

J. J. Choi "High-Q Bragg resonator CARM experiments on a long-pulse electron beam accelerator", Proc. SPIE 1514, 15th International Conference on Infrared and Millimeter Waves, 15140L (1 December 1990); https://doi.org/10.1117/12.2301431

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