The Coaxial Multipactor Experiment (CMX): A facility for investigating multipactor discharges

A multipactor discharge is a resonant condition for electrons in an alternating electric field. This discharge can be disruptive to radio frequency (RF) circuits, cavities, and resonators. The Coaxial Multipactor Experiment (CMX) investigates these discharges in parallel plate and coaxial transmission line geometries at frequencies from 40 to 150 MHz with goals of measuring the electron energy distributions. CMX has a unique experimental setup which allows the transmission line to pass continuously through a short vacuum region. Retarding potential analyzers with secondary electron suppression measure the electron current as a function of bias voltage. Both parallel plate and coaxial multipactor experiments provide the first detailed measurements of the electron energy distributions under a variety of RF frequencies and electrode materials.