Design of a capacitive main power coupler for RF superconducting accelerators

An updated main coupler has been designed for the superconducting accelerator of Free Electron Laser (FEL) project under construction in Peking University. A capacitive structure is chosen for the main coupler. Numerical investigation using CST Microwave Studio demonstrates the cold window part. The other nonstandard structures such as holding rods and antenna axe also optimized. The coupler uses a 95% purity Al(2)O(3) ceramic cold window. The VSWR (Vottage Standing Wave Ratio) is 1.02 at 1.3 GHz and the frequency bandwidth is 45 MHz with VSWR<1.1. The electric field intensity is 8.5x10(-2) kV/mm around the window with 20 kW Continuous Wave (CW) transmitted power. The Q(ext) is designed variable from 5x10(6) to 1x10(7).Physics, NuclearPhysics, Particles & FieldsSCI(E)中国科学引文数据库(CSCD)0ARTICLE7584-5883