Electroforming Klystron Cavities Using Machined and 3D Printed Mandrels

Abstract

Klystron amplifiers are critical for delivering GHz range radio frequency (RF) power for plasma heating. However, only recently has there been significant interest in raising the efficiency of klystrons. Traditional manufacturing methods remain expensive and time-consuming, limiting the development of high-efficiency designs. This thesis explores electroplated sacrificial mandrels as a rapid fabrication method for klystron cavities. Two mandrel types were evaluated: machined aluminum and 3D-printed plastics. RF performance was assessed via measurements of resonant frequency and unloaded quality factor. Cavities from aluminum mandrels showed resonant frequencies within ~25 MHz of predictions and unloaded Q-factors above 5000. Despite plating challenges, 3D-printed mandrels produced cavities with resonant frequencies within ~50 MHz of the target frequency and Q-factors between 3000–5000. These results demonstrate the viability of additive manufacturing for producing functional klystron cavities with reduced fabrication time.