LOW GAMMA TRANSITION OPTICS FOR THE SPS: SIMULATION AND EXPERIMENTAL RESULTS FOR HIGH BRIGHTNESS BEAMS

The single bunch transverse mode coupling instability (TMCI) at injection is presently one of the main intensity limitation for LHC beams in the SPS. A new optics for the SPS with lower transition energy yields an almost 3-fold increase of the slip factor at injection energyand thus a significantly higher TMCI threshold, as demonstrated both in simulations and in experimental studies. It is observed furthermore that the low gamma transition optics yields better longitudinal stability throughout the entire acceleration cycle. In addition, simulations predict a higher threshold for the electron cloud driven single bunch instability, which might become an important limitation for high intensity LHC beams with the nominal 25ns bunch spacing. This contribution gives a summary of the experimental and simulation studies, addressing also space charge effects and the achievable brightness with high intensity single bunch beams.