SLAC, Menlo Park, California, USA
Stanford University, Stanford, California, USA
We report on the development of a cryogenic X-band (11.424 GHz) accelerator to provide electron beams for Very High Energy Electron therapy. The distributed coupling linac is designed with a 135° phase advance, capable of producing a 100 MeV/m accelerating gradient in a one-meter structure using only 19 MW when operating at 77 K. This peak power will be achieved through pulse compression of a 5-8 MW few-µs pulse, ensuring compatibility with a commercial power source. We present designs of the cryogenic linac and power distribution system, as well as a room temperature pulse compressor using the HE11 mode in a corrugated cavity. We discuss scaling this compact and economical design into a 16 linac array that can achieve FLASH dose rates (> 40 Gy/s) while eliminating the downtime associated with gantry motion.
SLAC, Menlo Park, California, USA
The Electron Ion Collider requires a pre-injector linac to accelerate large electron bunches from 4 MeV up to 400 MeV over 35 m*. Currently this linac is being designed with 3 m long traveling wave structures, which provide a gradient of 16 MV/m. We propose the use of a 1 m distributed coupling design as a potential alternative and future upgrade path to this design. Distributed coupling allows power to be fed into each cavity directly via a waveguide manifold, avoiding on-axis coupling**. A distributed coupling structure at S-band was designed to optimize for shunt impedance and large aperture size. This design provides greater efficiency, thereby lowering the number of klystrons required to power the full linac. In addition, particle tracking analysis shows that this linac maintains lower emittance as bunch charge increases to 14 nC and wakefields become more prevalent. We present the design of this distributed coupling structure, as well as progress on structure manufacturing and characterization.
* F. Willeke, "Electron ion collider conceptual design report 2021," tech. rep., United States, 2021.
** S. Tantawi et al., Phys. Rev. Accel. Beams, vol. 23, p. 092001, Sep 2020.
