Contamination and conditioning of the prototype double spoke cryomodule for European Spallation Source

A superconducting Double Spoke Resonator (DSR) is the technology of choice in a low energy section of a high power proton linear accelerator. At the FREIA laboratory in Uppsala University, we have tested two DSRs in a prototype cryomodule for the European Spallation Source (ESS) project. It showed that the conditioning process of these cavity packages would be the key for the series production tests. In this paper, we present the conditioning procedure that we developed, and also describe the results with a special focus on the cross-contamination observed between two high-power couplers. This study defines a standard conditioning recipe for the series DSR production for ESS and also for future similar projects in the world.