Broadband MM radiation from beam driven strong turbulence

In order to measure broadband mm radiation emitted from relativistic beam electrons interacting with localized high frequency electrostatic fields in a strong Langmuir turbulent plasma, three types of spectrometer were prepared, a 6-channel filter-bank type covering K, Ka and U bands (18 – 60 GHz), a heterodyne type covering E band (60 – 90 GHz) and a full band detector covering F band (90 – 140 GHz). The spectrum of the mm radiation was measured radially, and also its angular distribution was measured at the end of the chamber. When the plasma frequency at the measuring position was about 13 GHz, the power level was high in K, Ka and U band range, but it decreased steeply in E and F band range. The angular distribution showed the radiation was intense in the axis. This implies the dipole moment of the caviton electric fields were not aligned to the beam direction.