A beam of charged particles (e.g., an electron beam) from a charged particle source can be selectively applied to a pair of electrodes. For example, the charged particles can be electrons that are directed toward a first electrode when the charge difference between the electrodes is in one state and...http://www.google.fr/patents/US7560716?utm_source=gb-gplus-shareBrevet US7560716 - Free electron oscillator
