Development of a Superconducting RF Multi-Spoke Cavity for Compact Light Sources

Superconducting radio frequency (SRF) accelerating cavities are being successfully used for acceleration of electron beams worldwide. The use of superconducting structures helps maximize the accelerating gradient, which is a highly desirable trait for applications involving linear accelerators or storage rings. Application of todays multi-spoke accelerating structures in future SRF electron linacs and synchrotrons will allow a further reduction in the overall size of acceleration sections without compromising its performance. Compact accelerators utilizing SRF cavities can be successfully used in the broad range of applications from x-rays machines for cancer therapy and sterilization, to tunable x-ray and gamma sources, to high energy electron accelerators and colliders. This SBIR proposal will develop a design of the 700 MHz superconducting multi-spoke cavity capable of accelerating electrons. In addition to building a cavity and associated cryomodule, Niowave will integrate a 5 watt cryocooler with the spoke cryomodule, resulting in a stand-alone spoke cavity based accelerating system operating at 4 K. Phase I demonstrated the technical feasibility of the project by completing the preliminary cavity and cryomodule designs. Phase II will finalize both designs, then fabricate and test the SRF multi-spoke cavity in the cryomodule. The cavity is designed to operate at 700 MHz and is capable of differential acceleration of electrons by ~12.5 MeV with electric and magnetic surface fields no more than ~46.7 MV/m and ~79.8 mT respectively. The integrated cryocooler system operates at 4 K. The cryogenic load can be significantly reduced by operating in a pulsed mode or by reducing the overall accelerating voltage.