INTENSE BEAM-PLASMA INTERACTION AS A SOURCE OF SUB-MILLIMETER RADIATION

Results of experimental and theoretical studies on the spectral content and polarization of submillimeter radiation generated in a dense (10¹⁴–10¹⁵ cm^–3) magnetized plasma by a high-power (~10¹⁰ W) relativistic (~10⁶ eV) electron beam are presented. The spectral and polarization characteristics of electromagnetic waves emitted from the plasma are analyzed in the frequency band (0.1– 0.5 THz) corresponding to the vicinity of the plasma frequency and its second harmonic. The observed radiation fluxes escaping from a beam-plasma system in the transverse and longitudinal direction agree with our theoretical insights based on the dominant excitation of upper-hybrid waves and their further conversion to electromagnetic radiation. For a strong turbulence, this conversion is mainly associated with two processes: the direct conversion of long-wavelength upper-hybrid weaves on small-scale density gradients and coalescence of these waves into electromagnetic ones. Theoretical predictions are found to be in quantitative agreement with experimental results.

Keywords:
electron beam relaxation in plasmas, strong Langmuir turbulence, scattering of plasma waves, generation of radiation in plasmas, radiation polarization.
УДК 533.9.01

INTENSE BEAM-PLASMA INTERACTION AS A SOURCE OF SUB-MILLIMETER RADIATION