Report on magnetic shielding for high quality superconducting resonators

This paper reports on the development of a passive and active magnetic shielding concept for a cryomodule housing four superconducting 704 MHz RF cavities. A test stand for magnetic measurements was then established along with a measurement procedure and used to quantify the magnetisation and shielding of the empty cryomodule. In addition to the original scope, a measurement device was developed and tested to quantify on small samples the magnetic flux, which remains trapped in superconductors after entering the Meissner state. These measurements can be used to better quantify the requirements for magnetic shielding of cryomodules and they allow for systematic studies of material treatments in order to increase flux expulsion, which in turn can reduce the need for magnetic shielding or increase the quality factor of cavities for a certain magnetic shielding configuration.