Development of radio frequency feedthrough prototype with high voltage and high vacuum for the HEPS strip-line kicker

Abstract

Strip-line kicker is a significant equipment in the on-axis injection scheme, adopted by the High Energy Photon Source (HEPS). The Radio Frequency (RF) feedthrough with high voltage and high vacuum is needed to connect strip-line kicker and fast high voltage pulser. This feedthrough needs to meet specific requirements, including electrical power transmission, high voltage capability, ultrahigh vacuum sealing, broadband performance, radiation resistance, and the ability to sustaining bake-out. The performance of the feedthrough directly impacts the quality of the beam deflection achieved by strip-line kicker. In this paper, the design of feedthrough and the development of two prototypes are presented, then RF cold test, helium leaking test, vacuum baking, and the high voltage test conducted on two prototypes are introduced. For improving radiation resistance, the design incorporates PEEK (Polyetheretherketone) as the insulation material. The RF cold test results demonstrate that the maximum reflected power is less than 8%, and the insertion loss is within 0.8 dB at 3 GHz. After subjecting the feedthrough to 48 h of baking at 200 °C, the vacuum leakage is measured to be lower than 3 × 10−12 Pa m3/s. In the high voltage test, the feedthrough prototype performs well, withstanding a peak amplitude of ±20 kV, a pulse bottom width of 4 ns, and a repetition frequency of 50 Hz.