Normal-conducting rf structure test facilities and results

The designs for a next-generation linear collider based on normal-conducting rf structures require operation at gradients much higher than those in existing linacs. For the NLC/JLC 11.4-GHz structures, the design unloaded gradient is 65 MV/m, which is about four times that of the 2.9-GHz SLAC Linac. The CLIC proposal using 30-GHz structures requires an even higher gradient, 170 MV/m. Both the CLIC and NLC/JLC groups are aggressively pursuing programs to develop structures that operate reliably at these gradients and also have acceptable efficiencies and transverse wakefields. Much progress has been made in the past few years, and this paper reviews the programs, test facilities and results from this research.