High Repetition-Rate Operation of a Compact Buncher for Microwaves

Recently, we have designed and built a new microwave tube; it has been given the name “Arletron.” It works in S-band, and we describe in this paper its operation. A 200-keV 1-kA annular electron beam (e-beam) is strongly bunched in a simple assembly of two pillbox cavities. The bunching occurs at the frequency of the -mode resonance of the system. An extracting cavity, inserted just downstream from the buncher, has been used to extract and to convert the kinetic energy of the beam into an RF wave that is then radiated by a conical antenna. The Arletron is a short and compact high-power microwave source whose repetition rate depends on the pulsed power system; operation at 100 Hz has been routinely achieved. The e-beam does not intercept grids or electrodes before being collected. MAGIC simulations predict that an Arletron can be, in principle, operated from S-band to C-band (2-6 GHz). Although a magnetic field is needed to propagate the beam, it is low enough to be produced by permanent magnets.