Advances Towards the Measurement and Control of LHC Tune and Chromaticity

Requirements for tune and chromaticity control in most superconducting hadron machines, and in particular the LHC, are stringent. In order to reach nominal operation, the LHC will almost certainly require feedback on both tune and chromaticity. Experience at RHIC has also shown that coupling control is crucial to successful tune feedback. A prototype baseband PLL tune measurement system, intended for the LHC, has recently been brought into operation at RHIC. We report on the performance of that system and compare it with the extensive accumulation of data from the RHIC 245MHz PLL. In addition the implementation of coupling and chromaticity feedback using PLL systems will be discussed.