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Beam-plasma instabilities and the beam-plasma dischargeUsing a new waves on magnetized beams and turbulence (WOMBAT) 0-450 eV electron gun, measurements bearing on the generation of beam-plasma discharge (BPD) are made. The new gun has a narrower divergence angle than the old, and the BPD ignition current is found to be proportional to the cross-sectional area of the plasma. The high-frequency instabilities are identified with the two Trivelpiece-Gould modes, (1959). The upper frequency is identified as a Cerenkov resonance with the upper Trivelpiece-Gould mode, and the lower frequency with a cyclotron resonance with the lower mode, in agreement with theoretical expectations. Convective growth rates are found to be small. A mechanism involving the conversion of a convective instability to an absolute one by trapping of the unstable waves in the density perturbations of the low-frequency waves, is suggested for the low-frequency wave control of the onset of the high frequency precursors to the BPD.
Document ID
19860053177
Acquisition Source
Legacy CDMS
Document Type
Reprint (Version printed in journal)
Authors
Kellogg, P. J.
(Australian National Univ. Canberra, Australia)
Boswell, R. W.
(Australian National University Canberra, Australia)
Date Acquired
August 12, 2013
Publication Date
May 1, 1986
Publication Information
Publication: Physics of Fluids
Volume: 29
ISSN: 0031-9171
Subject Category
Plasma Physics
Accession Number
86A37915
Funding Number(s)
CONTRACT_GRANT: NSF INT-84-18719
CONTRACT_GRANT: NAS5-25753
Distribution Limits
Public
Copyright
Other

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