An RF System for Landau Damping in the LHC

A Landau system in the LHC could significantly increase the longitudinal stability of the LHC beams in the absence of wide-band longitudinal feedback and provide more freedom to define the bunch parameters even during the initial stages of LHC operation. This technique for stabilizing beams, used already in many accelerators, has proven to be very useful in the SPS, raising the instability thresholds by a factor five. One of the luminosity upgrade paths for LHC requires an RF system at 1.2 GHz with ~ 60 MV per beam for bunch shortening. A much smaller RF system at this frequency with ~3 MV per beam would be sufficient to provide Landau damping. This Note analyses the possible benefits and recommends that an R & D programme, leading to one prototype cryostat per ring to be installed in the LHC machine, be launched as soon as possible.