Development and performance characterization of RF cavities, output coupler and RF section in a 5GHz, 250 kW klystron

Abstract

Klystron is microwave power amplifier widely used as RF source in particle accelerators, thermonuclear reactors and radars. The re-entrant cavity structures are widely used in klystron. They play a prominent role in deciding the performance of the device. Its design is carried out using SUPERFISH and MAGIC. The fabrication of cavities was carried out through machining of piece parts, brazing, and characterized through cold testing. Output section of klystron consist of reduce wave guide, step transformer and RF window assembly coupled with RF cavity. The coupling parameters loaded Q and VSWR are analytical calculated to match the cavity with output section. The simulation of output coupling carried out using CST microwave studio code. The analytical results are well matched with simulated results. An experimental assembly of RF cavity with output section fabricated. The design of RF section aims to get optimum power, gain, bandwidth and efficiency to meet desired specifications (1). A precise simulation of beam wave interaction in klystron is useful not only to understand its operation but also in development of tube with minimum iterations in fabrication. For this purpose a 1-D code AJDISK has been used to estimate different design parameters of RF section for desired tube performance. This information is used for simulation of complete tube including electron gun using MAGIC2D PIC code. The paper presents the results of simulation for cavity, output coupler and RF section.