Multiturn Measurements at the CERN SPS

The CERN SPS multiturn facility, based on the new beam orbit measurement system MOPOS, enables the User to acquire the position of the beam at each beam position monitor (BPM) over a number of consecutive turns. When the multiturn acquisition is synchronised with a perturbation imposed on the beam (for instance a fast kick), useful information about the optics of the SPS and the dynamic behaviour of the beam can be extracted from the data. A measurement of the amplitude and phase of the betatron oscillation at each BPM can be used to compare the theoretical optics functions with the real ones, and possibly to detect localised errors. Differences between two such measurements can be used to study the dependence on a variable parameter (e.g. beam intensity, beam energy, etc) and therefore indirectly measure quantities, like the impedance, distributed along the ring. Finally, due to 90 degrees phase advance lattice, plotting the positions measured at two consecutive BPMs against each other gives information about the behaviour of the beam in the transverse phase space. Results of measurements performed at the CERN SPS are presente

Tracking Study of the Effect of BPM Impedances in the SPS

Following the observation of a Transverse Mode Coupling Instability (TMCI) in the SPS [1, 2], a systematic estimate of the impedance of the various pieces of equipment installed in the machine has started. In this report the contribution of the Beam Position Monitor trapped modes to the global transverse impedance is considered. The trapped modes have been thus calculated with MAFIA and characterized with their resonator parameters. These impedances have been subsequently fed into the MOSES and HEADTAIL codes in order to evaluate the expected TMCI threshold in the SPS and compare it with the experimental observations

Baseline LHC machine parameters and configuration of the 2015 proton run

This paper shows the baseline LHC machine parameters for the 2015 start-up. Many systems have been upgraded during LS1 and in 2015 the LHC will operate at a higher energy than before and with a tighter filling scheme. Therefore, the 2015 commissioning phase risks to be less smooth than in 2012. The proposed starting configuration puts the focus on feasibility rather than peak performance and includes margins for operational uncertainties. Instead, once beam experience and a better machine knowledge has been obtained, a push in $\beta^*$ and performance can be envisaged. In this paper, the focus is on collimation settings and reach in $\beta^*$---other parameters are covered in greater depth by other papers in these proceedings.Comment: submitted for publication in a CERN yellow report (Proceedings of the LHC Performance Workshop - Chamonix 2014

Transverse Instabilities of the LHC Proton Beam in the SPS

The availability from the injectors of the proton beam required for the LHC era has allowed studying its transverse behaviour in the SPS. Profile and beam oscillation measurements evidenced the existence of strong transverse instabilities developing along the batch and inducing an emittance blow-up of increasing importance from the head to the tail of the batch. An intensity threshold, comparable to that observed for the development of the beam induced electron cloud, has been found for the onset of the above phenomena. The results of the measurements and their possible interpretation are presented

Considerations on the Transverse Emittance of the Fixed-Target Beam in the SPS in the PS2 Era

The range of the acceptable transverse emittances the Fixed-Target beams delivered to the SPS in the PS2 era is determined based on acceptance and other beam dynamics considerations in the SPS

Experimental Study of the Electron Cloud Instability at the CERN SPS

The electron cloud instability limits the performance of many existing proton and positron rings. A simulation study carried out with the HEADTAIL code revealed that the threshold for its onset decreases with increasing beam energy, if the 6D emittance of the bunch is kept constant and the longitudinal matching to the bucket is preserved. Experiments have been carried out at the CERN-SPS to study the dependence of the vertical electron cloud instability on the energy and on the beam size. The reduction of the physical transverse emittance as a function of energy is considered in fact to be the main reason for the unusual dependence of this instability on energy