Superconducting RF cavities and a 1.9 K cooling system for a femtosecond light source

The proposed femto-second light source consists of a re-circulating linac that delivers an electron beam to an arc of superconducting undulator magnets that deliver very short pulses of X-rays to materials science experiments. Superconducting RF cavities accelerate the electrons through the re-circulating linac. The design acceleration gradient for the 1300 MHz RF cavity system is 25 MV per meter. TESLA cavities operating in CW mode can provide this level of acceleration. This report presents the parameters of the proposed femto-second light source superconducting linac. Each nine-cell cavity will generate 44 W of AC loss at 1.9 K. The AC loss is added to the other losses in the accelerator cavity system. The superconducting RF cavity losses and linac refrigeration requirements are summarized in this report.