Demonstration of a cryocooler conduction-cooled superconducting radiofrequency cavity operating at practical cw accelerating gradients

We demonstrate practical accelerating gradients on a superconducting radiofrequency (SRF) accelerator cavity with cryocooler conduction cooling, a cooling technique that does not involve the complexities of the conventional liquid helium bath. A single cell 650 MHz Nb3Sn cavity coupled using high purity aluminum thermal links to a 4 K pulse tube cryocooler, generated accelerating gradients up to 6.6 MV/m at 100% duty cycle. The operation was carried out with the cavity-cryocooler assembly in a simple vacuum vessel, completely free of circulating liquid cryogens. We anticipate that this simple cryocooling technique will make the SRF technology accessible to accelerator researchers with no access to full-stack helium cryogenic systems. Furthermore, the technique can lead to SRF based compact sources of high average power electron beams for environmental and industrial applications.