Beam stability with separated beams at 6.5 TeV

We provide here a preliminary estimate of the available parameters space in terms of collimator settings, intensity, transverse emittances and bunch spacing, in order to allow stable single-beam and flat top operation at 6.5 TeV after the 2013-2014 long shutdown (LS1), assuming the machine will operate in similar conditions as in 2012 in terms of chromaticity, damper gain and damper bandwidth. As a starting point we use the current knowledge of the machine in terms of observed limits in single-beam operation, or in physics operation up to the beginning of the squeeze, and rescale them thanks to the impedance model obtained for the possible collimator settings scenarios. We show that only the 25 ns beam with a classical injection scheme can be stable with nominal collimator settings, while tight settings allow the operation with the BCMS (batch compression merging and splitting) 25 ns beam. The 50 ns beam will on the contrary probably require relaxed settings close to those of 2011.