Development of an X-band magnicon amplifier for the Next Linear Collider-cold cathode experiments and a thermionic design study

摘要

Summary form only given. The Naval Research Laboratory has been studying the operation of an 11 GHz frequency-doubling magnicon amplifier driven by a -650 kV, 225 A, 5.5-mm-diam. electron beam produced by a velvet cathode driven by a single-shot Marx generator. The magnicon circuit consists of a set of 5.56 GHz TM/sub 110/ deflection cavities (a drive cavity, two gain cavities, and a two-section /spl pi/-mode penultimate cavity) containing synchronously rotating modes that spin the beam up to high transverse momentum, followed by an 11.12 GHz TM/sub 210/ output cavity that uses a synchronously rotating mode to decelerate the electrons and generate microwave radiation. In the design, the electron spin-up develops progressively Through the deflection cavities. In the experiments, a plasma saturation effect was observed that limits the circulating power in each of the gain cavities to 10 kW. In order to overcome this low field saturation, the experiment was operated near the instability point of the penultimate cavity. We have designed a new thermionic magnicon experiment, incorporating an advanced high-convergence electron gun to produce a 500 kV, 200 A, 2-mm-diam. electron beam, an improved deflection cavity design, and an improved output cavity that employs side-coupling to extract the RF power through a pair of X-band waveguides separated by 135/spl deg/ around the azimuth of the cavity without destroying the symmetry of the rotating quadrupole mode. The predicted efficiency is /spl sim/60%.