• S. Hancock, M. Benedikt, C. Carli
  CERN, Geneva

The PS2 is proposed as a replacement for the ageing PS and will provide proton beams with kinetic energies up to 50 GeV. It must also deliver Pb⁵⁴⁺ ions, for which the revolution frequency swing will be more than a factor of two. The favoured rf scenario considers a 40 MHz accelerating system and is motivated by the possibility of chopping at up to 40 MHz in the SPL, the proposed proton injector. Using the same principal rf system for ions implies pushing for an unprecedented tuning range and the introduction of a new rf system in LEIR, the existing ion source. We present a solution to the disparate requirements of protons and ions based on a 40 MHz rf system with switchable tuning ranges to cover the large frequency swing required.

• C. Carli, M. Benedikt, S. Hancock
  CERN, Geneva
• V. Knuenz, I. Vonderhaid
  TU Vienna, Wien

Minimization of direct space charge tune shift at injection into the PS2 is important for the reduction of beam losses. A determining parameter for the tune shift is the bunching factor, defined as mean current over peak current for one RF period. Various longitudinal painting schemes for PS2 injection, all based on synchrotron motion, have been studied with respect to the resulting bunching factors. In particular, schemes using the SPL high-frequency chopper and different energy-spreads and offsets of the incoming beam as well as SPL beam energy modulations on have been simulated with the ESME code.

• S.S. Gilardoni, F. Arnold Malandain, E. Benedetto, T. Bohl, S. Cettour Cave, K. Cornelis, H. Damerau, F. Follin, T. Fowler, F. Franchi, P. Freyermuth, H. Genoud, R. Giachino, M. Giovannozzi, S. Hancock, Y. Le Borgne, D. Manglunki, G. Metral, L. Pereira, J.P. Ridewood, Y. Riva, M. Schokker, L. Sermeus, R.R. Steerenberg, B. Vandorpe, J. Wenninger
  CERN, Geneva

The Multi-Turn Extraction, a new type of extraction based on beam trapping inside stable islands in the horizontal phase space, has been commissioned during the 2008 run of the CERN Proton Synchrotron. Both single- and multi-bunch beams with a total intensity up to 1.4×10¹³ protons have been extracted with efficiencies up to 98%. Furthermore, injection tests in the CERN Super Proton Synchrotron were performed, with the beam then accelerated and extracted to produce neutrinos for the CERN Neutrino to Gran Sasso experiments. The results of the extensive measurement campaign are presented and discussed in details.

• C. Carli, A. Blas, A. Findlay, R. Garoby, S. Hancock, K. Hanke, B. Mikulec, M. Schokker
  CERN, Geneva

At present, for most LHC type physics beams, six buckets of the PS operated with harmonic number h=7 are filled in two transfers, and each of the PS Booster rings provides only one bunch. The scheme presented aims at replacing the double batch transfer by a single batch transfer and is of interest (i) for the nominal 25 ns LHC beams once the Booster injection energy has been increased after completion of Linac4 and (ii) already now for 50 ns and 75 ns LHC beams less demanding for the Booster in terms of beam brightness. Two bunches with the correct spacing must be generated in the Booster rings by superposition of an h=2 RF system and a smaller h=1 component. Theoretical considerations and first experimental results will be presented.

• C.M. Bhat
  Fermilab, Batavia
• F. Caspers, H. Damerau, S. Hancock, E. Mahner, F. Zimmermann
  CERN, Geneva

Funding: Fermi Research Alliance, LLC under Contract No. DE-AC02-07CH11359 with the U.S. Department of Energy and CARE-HHH

Motivated by the discussions on scenarios for LHC upgrades, beam studies on the stability of flat bunches in a double-harmonic RF system have been conducted in the CERN Proton Synchrotron (PS). Injecting nearly nominal LHC beam intensity per cycle, 18 bunches are accelerated on harmonic h=21 to 26 GeV with the 10 MHz RF system. On the flat-top, all bunches are then transformed to flat bunches by adiabatically adding RF voltage at h=42 from a 20 MHz cavity in anti-phase to the h=21 system. The voltage ratio V(h42)/V(h21) of about 0.5 was set according to simulations. For the next 140 ms, longitudinal profiles show stable bunches in the double harmonic RF bucket until extraction. Without the second harmonic component, coupled-bunch oscillations are observed. The flatness of the bunches along the batch is analyzed as a measure of the relative phase error between the RF systems due to beam loading. Measurements of electron cloud effects induced by the beam are also discussed. The results of beam dynamics simulations and their comparison with the measured data are presented.