EUROPEAN ORGANIZATION FOR NUCLEAR RESEARCH European Laboratory for Particle Physics LHC PILOT BUNCHES FROM THE CERN PS BOOSTER

For the first commissioning phase of the LHC, a single proton bunch is required. The production of this so-called “LHC pilot bunch” will follow a different scheme than the one of the nominal LHC proton bunch train. Both the transverse and the longitudinal LHC bunch characteristics should already be established in the PS Booster. The parameter space for the LHC pilot bunch spans a factor 66 in beam brightness. The intensity should be variable by a factor of 22 from 5.0⋅10 to 1.1⋅10, covering the range from the LHC quench limit up to the intensity of a nominal LHC bunch. The transverse emittances (at Booster ejection) should be adjustable in the range 0.85 πμm ≤ εnorm,rms ≤ 2.5 πμm, while the longitudinal emittance is kept constant at 0.3 eVs, slightly below the nominal one (0.35 eVs). To cover the whole parameter space, a mixture of several ingredients was required: intensity adjustment with low voltage rf-capture; definition of the transverse emittance with shavers; controlled blow-up followed by longitudinal shaving to define the longitudinal emittance. All beam variants were produced on harmonic two, with only one bunch being sent to the downstream accelerator chain. To cover also the lowest intensity side, the Linac beam was reduced by a factor 5 with a “sieve”. The pilot bunches corresponding to the “corners” of the parameter space and a few selected inner reference points were successfully produced in the PS Booster.