SPS BATCH SPACING OPTIMISATION

Abstract

Until 2015, the LHC filling schemes used the batch spacing as specified in the LHC design report. The maximum number of bunches injectable in the LHC directly depends on the batch spacing at injection in the SPS and hence on the MKP rise time. As part of the LHC Injectors Upgrade project for LHC heavy ions, a reduction of the batch spacing is needed. In  this direction, studies to approach the MKP design rise time of 150 ns (2-98%) have been carried out. These measurements gave clear indications that such optimisation, and beyond, could be done also for higher injection momentum beams, where the additional slower MKP (MKP-L) is needed. After the successful results from 2015 SPS batch spacing optimisation for the Pb-Pb run [1], the same concept was thought to be used also for proton beams. In fact, thanks to the SPS transverse feed back, it was already observed that lower batch spacing than the design one (225 ns) could be achieved. For the 2016 p-Pb run, a batch spacing of 200 ns for the proton beam with 100 ns bunch spacing was requested and finally used.
Thanks to the good performance of the 200 ns scheme, this was proposed as operational scenario for 2017 p-p physics with BCMS beams. In order to confirm the first observations and to evaluate the operational settings, the 2016 MD sessions were carried out.