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Measurements of Finite-Bandwidth Effects on a Parametric Instability

Results are presented for detailed experimental measurements of parametric instabilities driven by a broadband (stochastic) pump wave with a center frequency of 1.2 GHz in an argon-plasma-filled L-band waveguide. Both the growth rate and the saturation level of the ensemble-averaged high-frequency w...

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Bibliographic Details
Published in:Physical review letters 1977-09, Vol.39 (10), p.608-611
Main Authors: Mizuno, K., DeGroot, J. S.
Format: Article
Language:English
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Summary:Results are presented for detailed experimental measurements of parametric instabilities driven by a broadband (stochastic) pump wave with a center frequency of 1.2 GHz in an argon-plasma-filled L-band waveguide. Both the growth rate and the saturation level of the ensemble-averaged high-frequency waves were observed directly as a function of bandwidth. It is found that: (1) the ensemble-averaged high-frequency-wave energy grows exponentially, as if the waves were excited by a coherent pump wave, for sufficiently small pump bandwidths; (2) the growth rate decreases with increasing bandwidth as if only the fraction of the pump energy within the resonance region were available to drive the waves, in agreement with previous theoretical calculations; (3) the saturation level and suprathermal-electron production well above threshold are almost independent of bandwidth; and (4) the waves still grow for large bandwidths, but not exponentially. These experimental results are shown to be the same as those obtained by computer simulations.
ISSN:0031-9007
DOI:10.1103/PhysRevLett.39.608