Submillimeter Cerenkov radiation from a dc electron beam

A dc electron beam is shot at a low distance parallel to the plane surface of a dielectric. The Cerenkov radiation produced in the dielectric is observed. It has a continuous spectrum which was determined interferometrically in the 0.6...3 mm wavelength region. The measured dependences on beam voltage, current, and distance agree with theory within the experimental errors. The produced absolute spectral intensities were in the order of 10^?19 watt/cps.