Huang, G. Babel, S. Bachimanchi, R. Boyes, M. Brown, G.W. Campbell, K. Cha, D. Chase, B.E. Cullerton, E. Doolittle, L.R. Du, Q. Einstein, J. Hong, B. Hovater, C. Jones, J.A. Klepec, D.W. Ratti, A. Rivetta, C.H. Seidman, D.J. Serrano, C. Vytla, V.K. JACoW Geneva, Switzerland 978-3-95450-180-9 10.18429/JACoW-NAPAC2016-FRA2IO02 English 1292-1296 FRA2IO02 ion cavity controls LLRF feedback Contribution to a conference proceedings 2017 2017-01 http://dx.doi.org/10.18429/JACoW-NAPAC2016-FRA2IO02 https://jacow.org/napac2016/papers/fra2io02.pdf The LCLS-II is a CW superconducting linac under construction to drive an X-ray FEL. The energy and timing stability requirements of the FEL drive the need for very high precision RF control. This paper summarize the design considerations and early demonstration of the performance of the components and system we developed.