Optical Diagnosis Of Electric Fields In A Beam-Driven Turbulent Plasma

Amikam Dovrat; Xiaoling Zhai; Gregory Benford

doi:10.1117/12.951812

25 July 1989 Optical Diagnosis Of Electric Fields In A Beam-Driven Turbulent Plasma

Amikam Dovrat, Xiaoling Zhai, Gregory Benford

Proceedings Volume 1061, Microwave and Particle Beam Sources and Directed Energy Concepts; (1989) https://doi.org/10.1117/12.951812
Event: OE/LASE '89, 1989, Los Angeles, CA, United States

Abstract

Optical diagnostics using laser fluorescence techniques measure the RMS electric field in a superstrongly turbulent, relativistic beam-plasma system. This yields detailed mapping of <E2> as a function of axial position, z, radial location, r and time, t. This <E2(r,z,t)> allows studies of growth and evolution of turbulent fields, their diffusion and decay. Fluctuating electric fields occur when a 700 keV, 4 kA, 2 µs electron beam propagates into 20 cm diameter, 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: HeI 6632 Å and HeI 5015.7 Å. 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 R.M.S. field as the combined field of oscillation near the plasma frequency. Fields up to 28 kV/cm result. An analytical model of production of strong electric fields by beam-plasma instability, including modulational transfer in k-space, plasma heating, radiation and wave convection explains these results. Comparison between the experiment and the numerically integrated model is good.

Citation Download Citation

Amikam Dovrat, Xiaoling Zhai, and Gregory Benford "Optical Diagnosis Of Electric Fields In A Beam-Driven Turbulent Plasma", Proc. SPIE 1061, Microwave and Particle Beam Sources and Directed Energy Concepts, (25 July 1989); https://doi.org/10.1117/12.951812

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