Ge, M. Gonnella, D. Liepe, M. Sears, J. JACoW Publishing Geneva, Switzerland 2226-0366 978-3-95450-194-6 10.18429/JACoW-LINAC2018-TUPO058 English 470-472 TUPO058 cavity network SRF cryomodule linac Contribution to a conference proceedings 2019 2019-01 https://doi.org/10.18429/JACoW-LINAC2018-TUPO058 http://jacow.org/linac2018/papers/tupo058.pdf The quality factor of the nitrogen-doped SRF cavities for the LCLS-II project are strongly impacted by cool down speed. A sufficiently fast cool down speed can produce large thermal gradient across a cavity and sufficiently expel magnetic flux when the cavity wall passes from the normal-conducting to the superconducting state. However, instrumentation in LCLS-II production cryomodules has been kept at a minimum, and additional information during the cool down of the modules is therefore desirable. In this work, we study if and how RF data can be used during cavity cool-down to determine the transition speeds of the individual cavities in the LCLS-II linac.