Microwave emission and beam propagation measurements in a high-power relativistic electron beam-plasma system

Journal Article · Fri Apr 01 04:00:00 EST 1988 · IEEE Trans. Plasma Sci.; (United States)

DOI:https://doi.org/10.1109/27.3817· OSTI ID:6988895

Di Capua, M S; Camacho, J F; Fulkerson, E S; Meeker, D

The authors measured microwave emission from a system consisting of an unmagnetized plasma (T/sub e/ approx. = 1 eV, 0.8 < n/sub e/ < 2.3 x 10/sup 11/ cm/sup -3/) and a propagating electron beam (I/sub b/ approx. = 50 kA, V/sub b/ approx. = 1.4 MV, J/sub b/ approx. = 280 A/cm/sup 2/, t/sub rise/ approx. = 35 ns, t/sub pulse/ approx. = 60 ns). A 93-cm/sup 2/ velvet cathode, with an anode-cathode gap of 5.9 cm, injects the electron current into the plasma through an aluminized Mylar anode. The authors measure diode voltage and current in the 6-..cap omega.. water dielectric accelerator and net current through the beam-plasma system. The plasma is produced by a 90-..mu..s, 90-A current pulse, emitted from a thermionic LaB/sub 6/ electron source, which preionizes a 0.8 < rho/sub o/ < 4.6 mT argon fill in a 1-m-long, 15-cm-diameter Lucite tube. A microwave spectrometer detects the radio-frequency output in the 2-18, 18-26, and 26-47 GHz bands, which a set of filters then separates into narrower subbands. The emission takes place in two distinct phases. The 2-6-GHz output, which includes f/sub rho/, rises promptly with the current pulse and then decays. At 6 GHz and above, a low-level microwave prepulse appears simultaneously with the 2-6-GHz output. This output rises sharply 25 ns after the current pulse begins and includes frequencies out to and beyond 40 GHz. The radio-frequency output falls off before the current pulse ends. The microwave intensity decays monotonically with frequency.

• Research Organization: Lawrence Livermore National Lab., Univ. of California, Livermore, CA (US)
• OSTI ID: 6988895
• Journal Information: IEEE Trans. Plasma Sci.; (United States), Journal Name: IEEE Trans. Plasma Sci.; (United States) Vol. 16:2; ISSN ITPSB
• Country of Publication: United States
• Language: English

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70 PLASMA PHYSICS AND FUSION TECHNOLOGY
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