Abstract
| The longitudinal beam parameters are proposed for the LHC re-commissioning and
operation in 2015, based on the experience obtained from operation and MD
results during LHC Run 1. Controlled longitudinal emittance blow-up is necessary
during the whole ramp to 6.5 TeV. The value of the longitudinal emittance is
defined by beam stability and IBS, and bunch length and RF voltage by particle
losses, beam induced heating and experiments requirements. The impact of the
longitudinal parameters on luminosity will be also discussed here. Beam induced
heating limitations during LHC run 1 are reviewed and an update on the
mitigation measures taken during LS1 is presented. The situation in 2015 is
expected to be more favourable due to all improvements made and potential issues
would be mainly caused by unexpected non-conformities. In addition, more devices
are equipped with temperature sensors that will allow us to monitor beam induced
heating and react early to try and prevent damage to the equipment. Since
further increase of bunch length leads to beam lifetime degradation, a special
controlled emittance blow-up that flattens the bunch profile is also considered
for beam induced heating mitigation. |