Excitation of pure electron plasma waves by modulate electron beams

A new type of exciter consisting of electron beams for launching electron plasma waves is investigated experimentally and theoretically. When fast electron sheet beams, modulated at a prescribed frequency, are injected into plasmas, electron plasma waves are found to be excited nearly perpendicularly to the electron beams. Compared with a mesh excitation, we found that the beam excitation has several merits: it hardly excites ballistic modes, the direct coupling due to an electrostatic induction with another probe is small, and it can even be used in a very hot plasma.