Recent results from the plasma microwave electronics program at the U. of Maryland

Conference · Sat Dec 31 04:00:00 EST 1994

OSTI ID:51774

Carmel, Y; Antonsen, Jr, T M; Rodgers, J ^[1]

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1. Univ. of Maryland, College Park, MD (United States). Inst. for Plasma Research; and others

The authors` research encompasses an intensive experimental and theoretical study of a plasma-filled, relativistic backward wave oscillator (BWO) operating at a frequency of 8.5 GHz. The authors are developing systematic understanding of the operation of such devices and their scaling with parameters to enable future design of future, larger diameter overmoded devices at the multi-gigawatt power levels. When loaded with a background plasma, the measured microwave interaction efficiency rose from a maximum of about 20% (in vacuum) to 40%. Efficiency enhancement was observed over a background plasma density between 2 {times} 10{sup 9} and 4 {times} 10{sup 10} cm{sup {minus}3}. The starting current of the vacuum BWO (about 80 A at 400 kV) was hardly affected by the background plasma. Efficient operation at greatly reduced guiding magnetic field (down to 1 kGauss) was demonstrated. They have measured the guiding magnetic field values under which the Cerenkov and the cyclotron synchronism conditions are simultaneously satisfied. The radiation in plasma filled backward wave oscillators is sufficiently intense to trigger a nonlinear parametric decay process which may explain the improved efficiency of these devices compared with similar vacuum BWOs. The proposed parametric process is a form of Raman decay in which a large amplitude mode of the cavity decays into a plasma wave and a lower frequency mode of the cavity. The authors have developed a simple model for this process and they will show comparisons of the results of simulations of the model with the results of experiments.

• OSTI ID: 51774
• Report Number(s): CONF-940604--; ISBN 0-7803-2006-9
• Country of Publication: United States
• Language: English

Related Subjects

42 ENGINEERING
BACKWARD WAVE TUBES
COMPARATIVE EVALUATIONS
COMPUTERIZED SIMULATION
MATHEMATICAL MODELS
PARAMETRIC INSTABILITIES
RESEARCH PROGRAMS
SCALING LAWS