Low-temperature Bonding Technique for High-Gradient Normal Conducting Accelerator Structures

Very high gradients are required for multi-TeV future colliders. The main limit to achieving high gradients in normal conducting accelerator structures is RF breakdown. Recent research on high- gradient RF structures indicates that hard copper alloys provide significant advantages over annealed copper. There are currently no well-established low temperature bonding techniques that preserve the hardness, surface finish and cleanliness required for high gradient operation. 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. RF design of a SLAC compatible test structure has been performed. EBW process parameters for CuAg have been studied and areas for further work have been identified. A CuAg SW test structure has been manufactured with EBW and validated. A conceptual RF design for a TW variant of this design style has been performed. Final optimization of the SW RF design will be performed. Further EBW process parameters will be refined and designs for ancillary components will be developed and tested. Several iterations of the SW structure will be manufactured and high power tested. A TW structure designed for CLIC parameters will be designed and manufactured. 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-proliferation systems, compact free-electron lasers, and medical imaging and therapy systems. This project will develop more efficient, lower cost manufacturing technologies for particle accelerators with uses ranging from high energy particle colliders to medical therapy sources