Low-temperature bonding technique for high-gradient normal conducting accelerator structures

Reaching multi-TeV energies in future collider applications utilizing Radio Frequency (RF) accelerators of reasonable length and cost will require achieving very high accelerating gradients. The main limit to achieving high gradients in normal conducting accelerator structures is RF breakdown. Recent research on high-gradient RF accelerating structures indicates that the use of hard copper alloys provides significant advantages over annealed copper. However, there are currently no well established low temperature bonding techniques that preserve the hardness, surface finish and cleanliness required for high gradient operation. Technical Approach This project will develop the design and manufacturing process to fabricate a novel high-gradient normal conducting (copper-silver alloy) RF accelerating structure utilizing electron-beam welding (EBW). Further, the accelerating structure will be manufactured in 2 halves, which will reduce manufacturing cost compared to standard multi-cell manufacturing methods. Phase I Plans A basic 3 cell version of the cavity will be manufactured from a silver bearing copper alloy and cold tested to characterize the basic RF parameters. RF engineering of a full size structure will be performed and preparations for high power testing for breakdown characterization of both the 3 cell and full size structure will be planned along with preliminary full structure ermomechanical engineering to ensure feasibility of manufacture Commercial Applications and Other Benefits The proposed manufacturing technology and structure design development would have immediate applications in linear accelerators (linacs) for high energy particle colliders, compact higher-energy nuclear non- roliferation systems, compact free-electron lasers, and medical imaging and therapy systems. Key Words High gradient, accelerator, RF, NCRF, hard copper alloy, break down, x-band