Optical diagnosis of electric fields in a beam-driven turbulent plasma

Journal Article · Fri Dec 01 04:00:00 EST 1989 · Physics of Fluids B: Plasma Physics; (USA)

DOI:https://doi.org/10.1063/1.859183· OSTI ID:5215541

Dovrat, A; Benford, G ^[1]

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1. Department of Physics, University of California, Irvine, California 92717 (US)

Optical diagnostics using laser fluorescence techniques are used to measure the rms electric field in a superstrongly turbulent, relativistic beam--plasma system. This yields the mapping of {l angle}{ital E}{sup 2}{r angle} as a function of radial location {ital r} and time {ital t}. This {l angle}{ital E}{sup 2}({ital r},{ital t}){r angle} allows studies of growth and evolution of turbulent fields, their diffusion, and decay. Fluctuating electric fields occur when a 700 keV, 4 kA, 2 {mu}sec electron beam propagates into a 20 cm diam, 1.5 m long drift tube filled with 10 mTorr of helium plasma. Stark effect shifts appear in suitable forbidden and allowed transitions, originating from the same upper energy level for the measurement: He I 6632 A and He I 5015.7 A. The spectral bandwidth includes the forbidden line and its satellites. Using the ratio of the intensity of the forbidden plus satellite lines, to the allowed line intensity, yields the rms field as the combined field of oscillation near the plasma frequency. Fields up to 28 kV/cm result. These results can be explained by an analytical model of production of strong electric fields by beam--plasma instability, including modulational transfer in {ital k} space, plasma heating, radiation, and wave convection. Comparison between experiment and the numerically integrated model shows good agreement.

• OSTI ID: 5215541
• Journal Information: Physics of Fluids B: Plasma Physics; (USA), Journal Name: Physics of Fluids B: Plasma Physics; (USA) Vol. 1:12; ISSN 0899-8221; ISSN PFBPE
• Country of Publication: United States
• Language: English

Related Subjects

70 PLASMA PHYSICS AND FUSION TECHNOLOGY
700102* -- Fusion Energy-- Plasma Research-- Diagnostics
BEAM-PLASMA SYSTEMS
ELECTRIC FIELDS
ELEMENTS
FLUIDS
FLUORESCENCE
GASES
HELIUM
INSTABILITY
LUMINESCENCE
MAPPING
NONMETALS
NUMERICAL SOLUTION
PLASMA
PLASMA DIAGNOSTICS
PLASMA SIMULATION
RARE GASES
RELATIVISTIC PLASMA
SIMULATION
TURBULENCE