Observation and Study of Low-Frequency Oscillations in a 1.5-MW 110-GHz Gyrotron

We report the observation of low-frequency oscillations (LFOs) in the range 165-180 MHz in a 1.5-MW 110-GHz gyrotron operating in 3-mus pulses. The oscillations have been measured by a capacitive probe located just before the entrance to the cavity. The LFOs are observed only in a narrow region of b...

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Bibliographic Details
Published in:IEEE transactions on plasma science 2009-07, Vol.37 (7), p.1219-1224
Main Authors: Cerfon, A.J., Eunmi Choi, Marchewka, C.D., Mastovsky, I., Shapiro, M.A., Sirigiri, J.R., Temkin, R.J.
Format: Article
Language:English
Subjects:
Applied sciences
Beams (radiation)
Cyclotrons
Electric potential
Electric power
Electromagnetic heating
Electron beams
Electron traps
Electronic tubes, masers
Electronics
Electrons
Entrances
Exact sciences and technology
Frequency
Fusion
Fusion reactors
gyrotron
Gyrotrons
high-power microwave source
Holes
low-frequency oscillations (LFOs)
Oscillations
Plasma
Probes
Space probes
Studies
Time domain analysis
trapped electrons
Voltage
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Summary:We report the observation of low-frequency oscillations (LFOs) in the range 165-180 MHz in a 1.5-MW 110-GHz gyrotron operating in 3-mus pulses. The oscillations have been measured by a capacitive probe located just before the entrance to the cavity. The LFOs are observed only in a narrow region of beam parameter space, at voltages between 45 and 60 kV, where no microwave emission occurs. When the gyrotron operates near 96 kV, with high output power, they are not seen. The variation of the frequency of the oscillations with electron beam voltage and magnetic compression was measured, and the results are reported. Time-domain analysis of the probe signal shows the influence of the beam current and cathode voltage on the time of onset of the oscillations. The amplitude of the time-domain signal indicates that the trapped electron current associated with the LFOs represents a few percent of the total electron current.
ISSN:0093-3813
1939-9375
DOI:10.1109/TPS.2009.2020903