Summary of the 4th LHC Crab Cavity Workshop "LHC-CC10"

The 4th workshop on crab cavities for the LHC high-luminosity upgrade project HL-LHC (LHC-CC10) was held from 15 to 17 December 2010 at CERN, Geneva, Switzerland. This document outlines the key conclusions from the LHC-CC10 workshop and summarizes each individual session based on the final presentations by the session conveners and on the subsequent discussions. At LHC-CC10, local crab crossing with the aid of 400 MHz deflecting SRF cavities was identified as the baseline tool for geometric luminosity-loss compensation and luminosity levelling for the HL-LHC. Associated key issues such as machine protection and robust operational scenarios still have to be studied in detail, so as to identify and mitigate potential beam-dynamics or technology limits on implementing and fully exploiting crab crossing at the LHC. Also at LHC-CC10, the decision was taken not to install a KEK-B crab cavity in the SPS. However, it was recommended that all measures to test future LHC prototype cavities with and without beam outside the LHC be taken in order to ensure robust operation of the crab RF structures in the LHC.