• E.N. Shaposhnikova, G. Arduini, J. Axensalva, E. Benedetto, S. Calatroni, P. Chiggiato, K. Cornelis, P. Costa Pinto, B. Henrist, J.M. Jimenez, E. Mahner, G. Rumolo, M. Taborelli, C. Yin Vallgren
  CERN, Geneva

Electron cloud build-up is a major limitation for the operation of the SPS with LHC beam above nominal intensity. These beams are envisaged in the frame of the LHC luminosity upgrade and will be available from the new injectors LPSPL and PS2. A series of studies have been conducted in order to identify possible means to suppress electron multipacting by coating the existing SPS vacuum chambers with thin films of amorphous carbon. After a description of the experimental apparatus installed in the SPS, the results of the tests performed with beam in 2008 will be presented.

• E. Métral, G. Arduini, F. Arnold Malandain, W. Höfle, D. Manglunki
  CERN, Geneva

For several years, a large variety of beams have been prepared in the LHC injectors, such as single-bunch and multi-bunch beams, with 25 ns, 50 ns and 75 ns bunch spacings, nominal and intermediate intensities per bunch. As compared to the nominal LHC beam (i.e. with nominal bunch intensity and 25 ns spacing) the other beams can be produced with lower transverse emittances. Beams of low transverse emittances are of interest during the commissioning phase for aperture considerations and because of the reduced long-range beam-beam effects. On the other hand machine protection considerations might lead to prefer nominal transverse emittances for safe machine operations. The purpose of this paper is to present the results of controlled transverse emittance blow-ups using the transverse feedback and octupoles. The procedures tested in the SPS in 2008 allow to tune the transverse emittances up to nominal values at SPS extraction.

• R. Calaga
  BNL, Upton, Long Island, New York
• G. Arduini, E. Métral, G. Papotti, D. Quatraro, G. Rumolo, B. Salvant, R. Tomás
  CERN, Geneva

Funding: This work has been partially performed under the auspices of US department of energy

Measurements of transverse impedance in the SPS to track the evolution over the last few years show discrepancies compared to the analytical estimates of the major contributors. Recent measurements to localize the major sources of the transverse impedance using intensity dependent optics are presented. Some simulations using HEADTAIL to understand the limitations of the reconstruction and related numerical aspects are also discussed.

• B. Salvant
  EPFL, Lausanne
• G. Arduini, H. Burkhardt, H. Damerau, W. Höfle, E. Métral, G. Papotti, G. Rumolo, B. Salvant, R. Tomás, S.M. White
  CERN, Geneva
• R. Calaga, R. De Maria
  BNL, Upton, Long Island, New York

The upgrade of the CERN Large Hadron Collider (LHC) would require a four- to fivefold increase of the single bunch intensity presently obtained in the Super Proton Synchrotron (SPS). Operating at such high single bunch intensities requires a detailed knowledge of the sources of SPS beam coupling impedance, so that longitudinal and transverse impedance reduction campaigns can be planned and performed effectively if needed. In this paper, the transverse impedance of the SPS is studied by injecting a single long bunch into the SPS, and observing its decay without RF. This particular setup enhances the resolution of the frequency analysis of the longitudinal and transverse bunch signals acquired with strip line couplers connected to a fast data acquisition. It also gives access to the frequency content of the transverse impedance. Results from measurements with short and long bunches in the SPS performed in 2008 are compared with simulations and theoretical predictions.

• B. Salvant
  EPFL, Lausanne
• D. Alesini, M. Migliorati, B. Spataro
  INFN/LNF, Frascati (Roma)
• G. Arduini, C. Boccard, F. Caspers, A. Grudiev, O.R. Jones, E. Métral, G. Rumolo, B. Salvant, C. Zannini
  CERN, Geneva
• R. Calaga
  BNL, Upton, Long Island, New York
• F. Roncarolo
  UMAN, Manchester

A detailed knowledge of the beam coupling impedance of the CERN Super Proton Synchrotron (SPS) is required in order to operate this machine with a higher intensity for the foreseen Large Hadron Collider (LHC) luminosity upgrade. A large number of Beam Position Monitors (BPM) is currently installed in the SPS, and this is why their contribution to the SPS impedance has to be assessed. This paper focuses on electromagnetic simulations and bench measurements of the longitudinal and transverse impedance generated by the horizontal and vertical BPMs installed in the SPS machine.