Design of Diamond-lined Accelerator Structure Test Cavity

For a high-gradient normal-conducting accelerator structure for a future multi-TeV linear collider, the main limitation to achievement of high acceleration gradient is RF breakdown. In an attempt to increase the gradient beyond limits that are acceptable for metallic structures, a diamond-lined structure is suggested. The published DC breakdown limit for CVD diamond is ~2 GV/m, but the limit has never been determined for RF fields. Here we present a design for a 34-GHz diamond-lined symmetric rectangular test cavity, operating in the LSM216 mode with a side-wall input coupler. The goal is to produce electric fields up to 1 GV/m at the diamond surfaces with ~10 MW of RF input power supplied by the Omega-P/Yale 34-GHz magnicon for experimental tests to determine the breakdown strength of CVD diamond at mm-wavelengths.