Impedance effects on beam stability

In 2012, attempts to increase the bunch intensity, decrease the emittance and reduce the collimators gaps in the LHC, will potentially make the detrimental effects due to the machine impedance more critical. Extrapolating the data accumulated in 2010 and 2011, in several foreseen scenarios, the headtail modes at top energy will require an increase of the current in the octupoles installed in the LHC. In the worst case, instead of around 200 A in the defocusing octupoles and − 200 A in the focusing ones as at the end of the 2011 physics run, the octupoles’ current will have to be increased to around ± 450 A.