KLYSTRON

thermionic electron tube making use of the controlled speed of a stream of electrons. The electrons are originally accelerated to high velocity by a potential of several hundred volts and enter a narrow gap that forms part of a cavity resonator system, where they are acted upon by a radio frequency field, causing a bunching-up effect. Amplitude modulation of the electrons in their bunched-up state induces a strong signal as the stream passes through the gap of a second resonator. Klystrons are used in ultra high-frequency circuits, where they can produce oscillations up to 400,000 megahertz (400,000 megacycles per second), in the short microwave range.