Phase locking of a second harmonic gyrotron using a quasi-optical circulator
- California Inst. of Technology, Pasadena, CA (United States). Jet Propulsion Lab.
- Univ. of Maryland, College Park, MD (United States). Inst. for Plasma Research
- Florida A and M Univ., Tallahassee, FL (United States)
Phase locking of a high power pulsed gyrotron oscillator through the use of a quasi-optical circulator was investigated. A second harmonic gyrotron which features a novel complex cavity, operating at 34.5 GHz, was used in the experiment. The quasi-optical circulator consisted of a 5.75 in. diameter ferrite disk biased with a one kilogauss permanent magnet. A polarizing grid was used to separate the input and output signals in the circulator. In order to couple the gyrotron oscillator output efficiently to the quasi-optical system, a number of mode converters, TE{sub 03}-TE{sub 02}, TE{sub 02}-TE{sub 01}, TE{sub 01}-TM{sub 11}, and TM{sub 11}-HE{sub 11}, were required. The insertion loss of the circulator and mode converter chain was approximately 1 dB, and an isolation exceeding 25 dB was achieved. In addition, a low power WR28 waveguide isolator was inserted in the injection signal path, providing an additional 35 dB of isolation, for a total isolation of 60 dB. The injection signal was provided by a synthesized signal generator and a 100 Watt travelling wave tube amplifier. A sample of the gyrotron output signal was obtained through an additional horn and mixed with a sample of the injection signal, producing a difference signal. The injection signal was swept slowly through a known frequency range while the difference signal was recorded. The recorded signals were analyzed off-line, and the locking bandwidth was determined. Experiments were performed for injection powers from 0--60 Watts, and a gyrotron output power of approximately 80--100 kW. Phase locking was observed for all non-zero injection powers.
- OSTI ID:
- 116408
- Report Number(s):
- CONF-950793--; ISBN 0-8194-1916-8
- Country of Publication:
- United States
- Language:
- English
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