Zhao, L. Daly, E. Davis, G.K. Eremeev, G.V. Reilly, A.V. Valente-Feliciano, A-M. Wilson, K.M. JACoW Publishing Geneva, Switzerland 2226-0366 978-3-95450-194-6 10.18429/JACoW-LINAC2018-MOPO019 English 71-73 MOPO019 cavity SRF FEL cryomodule experiment Contribution to a conference proceedings 2019 2019-01 https://doi.org/10.18429/JACoW-LINAC2018-MOPO019 http://jacow.org/linac2018/papers/mopo019.pdf Inter-cavity copper plated bellows are part of the LCLS-II cryomodule beamline components. Since the bellows are close to superconducting radio frequency (SRF) cavities during accelerator operation, it is desirable that these bellows have similar cleanliness as SRF cavi-ties. Studies have been done to help evaluate bellows interior cleanliness after the standard bellows cleaning procedure at Jefferson Lab.