Niowave, Inc. — Department of Energy SBIR Phase I: Many lines of research currently ongoing at storage ring light sources would benefit from

Description

Many lines of research currently ongoing at storage ring light sources would benefit from intense, tunable, few picoseconds x-ray pulses for time-domain experiments. The use of a deflecting cavity has several advantages over other proposals to produce these pulses. A crab cavity does not accelerate the bunch, but instead deflects the head of the bunch relative to the tail. This kind of chirp in the transverse momentum imposes an angle-time correlation on the light emitted from the undulator that can be used for time-domain experiments or manipulated with proper x-ray optics to produce ps-scale x-ray pulses. This SBIR proposal seeks to develop a superconducting crab cavity for this use in light sources. Here, a quarter-wave geometry is proposed that operates in the fundamental resonant mode, unlike the more conventional elliptical cavities that have been used for this application, which operate on a higher-order mode and require dampers for the fundamental mode. Further, the quarter-wave geometry has a very different spectrum of higher-order modes than elliptical shapes. Taking advantage of this sparse mode spectrum, an innovative design is proposed with a large beam pipe to allow all higher-order modes to propagate to absorbers at room temperature outside the cryomodule. The quarter wave structure is also efficient and compact, often relevant considerations for crabbing cavities.