Effect of beam modulation on a broadband MM radiation from a strong beam-turbulent plasma

High-power broadband millimeter-wave radiation is emitted from a plasma in a strong Langmuir turbulence state driven by an intense relativistic electron beam (1.4 MeV, 10 MA, and 30 ns). In order to ascertain that the radiation is due to interaction of modulated beam with caviton fields, the radiation and the beam modulation were measured with two spectrometers covering 18 to 140 GHz. The radiation spectrum had nearly flat spectrum up to about 40 GHz and declined steeply above it. The beam modulation is measured by two methods: observation of spectrum of waves excited in a waveguide pickup and observation of spectrum of synchrotron radiation. Both spectra were similar to the radiation spectrum. Discussion is given on the experimental results in connection with the collective Compton boosting model