Correlation between high-power microwave radiation and high frequency electric fields in a strong beam-plasma turbulence

We show a direct evidence that high-power broadband microwave radiation which is emitted when an intense relativistic electron beam (IREB) is injected into a plasma correlates strongly to the electric fields in cavitons in the plasma. An IREB (1.5 MV, 25 kA, 30 ns) was injected into an unmagnetized plasma. The drift chamber was filled with helium gas of 20 mTorr. High-power microwave radiation in a frequency range from 26.5 GHz to 40.0 GHz was measured simultaneously with high frequency turbulent electric fields. We found the strong Langmuir turbulence state is the necessary condition for the high-power broadband microwave radiation. Moreover high-power microwave radiation depends on W/np1/2 but not linearly, where W is the electrostatic energy density ratio which was obtained from the ratio of electrostatic energy density obtained from the Stark shifts of HeI 5015.7 Å to the plasma energy density and np is the plasma density.