Detailed spectra of high-power broadband microwave radiation from interactions of relativistic electron beams with weakly magnetized plasmas

Journal Article · Thu Dec 01 00:00:00 EST 1983 · Phys. Fluids; (United States)

DOI:https://doi.org/10.1063/1.864134· OSTI ID:5385253

Kato, K G; Benford, G; Tzach, D

Prodigious quantities of microwave energy distributed uniformly across a wide frequency band are observed when a relativistic electron beam (REB) penetrates a plasma. Typical measured values are 20 MW total for ..delta nu..approx. =40 GHz with preliminary observations of bandwidths as large as 100 GHz. An intense annular pulsed REB (Iapprox. =128 kA; rapprox. =3 cm; ..delta..rapprox. =1 cm; 50 nsec FWHM; ..gamma..approx. =3) is sent through an unmagnetized or weakly magnetized plasma column (n/sub plasma/approx.10/sup 13/ cm/sup -3/). Beam-to-plasma densities of 0.01< or =n/sub beam//n/sub plasma/< or =2 are used, the higher values of this range being an unconsidered region for most previous theoretical and experimental efforts. For these higher n/sub b//n/sub p/ values, the observed emission with ..omega..>>..omega../sub p/ and weak harmonic structure is wholly unanticipated from Langmuir scattering or soliton collapse models. A model of Compton-like boosting of ambient plasma waves by the beam electrons, with collateral emission of high-frequency photons, qualitatively explains these spectra. Power emerges largely in an angle approx.1/..gamma.., as required by Compton mechanisms. As n/sub b//n/sub p/ falls, ..omega../sub p/-2..omega../sub p/ structure and harmonic power ratios consistent with soliton collapse theories appear. With further reduction of n/sub b//n/sub p/ only the ..omega../sub p/ line persists.

• Research Organization: Department of Physics, University of California, Irvine, California 92717
• OSTI ID: 5385253
• Journal Information: Phys. Fluids; (United States), Vol. 26:12
• Country of Publication: United States
• Language: English

Related Subjects

70 PLASMA PHYSICS AND FUSION TECHNOLOGY
BEAM-PLASMA SYSTEMS
MICROWAVE RADIATION
PLASMA DIAGNOSTICS
SPECTROMETERS
ELECTRON BEAMS
MAGNETIZATION
MICROWAVE SPECTRA
POWER
RELATIVISTIC RANGE
BEAMS
ELECTROMAGNETIC RADIATION
ENERGY RANGE
LEPTON BEAMS
MEASURING INSTRUMENTS
PARTICLE BEAMS
RADIATIONS
SPECTRA
700102* - Fusion Energy- Plasma Research- Diagnostics