• B. Mikulec, M. Chanel, A. Findlay, K. Hanke, D. Quatraro, G. Rumolo, J. Tan, R. Tomás
  CERN, Geneva

The CERN Proton Synchrotron Booster (PSB) has been running for more than 30 years. Originally designed to accelerate particles from 50 to 800 MeV, later upgraded to an energy of 1 GeV and finally 1.4 GeV, it is steadily being pushed to its operational limits. One challenge is the permanent demand for intensity increase, in particular for CNGS and ISOLDE, but also in view of LINAC4. As it is an accelerator working with very high space charge during the low energy part of its cycle, its operational conditions have to be precisely tuned. Amongst other things resonances must be avoided, stop band crossings optimized and the machine impedance minimized. Recently, an operational intensity record was achieved with >4.25·10¹³ protons accelerated. An orbit correction campaign performed during the 2007/2008 shutdown was a major contributing factor to achieving this intensity. As the PSB presently has very few orbit correctors available, the orbit correction has to be achieved by displacing and/or tilting some of the defocusing quadrupoles common to all 4 PSB rings. The contributing factors used to optimize performance will be reviewed.

• D. Quatraro, A. Blas, M. Chanel, A. Findlay, B. Mikulec, G. Rumolo
  CERN, Geneva

To understand one contribution to the intensity limitations of the CERN Proton Synchrotron Booster (PSB) in view of its operation with beams from Linac 4, the impedance of the machine has been characterized. Measurements of tune shift as a function of the intensity have been carried out in order to estimate the low frequency imaginary part of the impedance. Since the PSB is a low energy machine, these measurements have been done at two different energies,so as to enable us to disentangle the effect of the indirect space charge and resistive wall from the contribution of the machine impedance. An estimation of the possible resonant peaks in the impedance spectrum has been made by measuring a fast instability in Ring 4.

• C. Carli, M. Aiba, M. Chanel, B. Goddard, M. Martini, W.J.M. Weterings
  CERN, Geneva

The motivation for the construction of CERN Linac4 is to improve the performance of the PSB by raising the injection energy and implementing a new H^- charge exchange multiturn injection scheme. Strategies to design the H^- charge exchange injection hardware and, in particular, to mitigate perturbations of the lattice will be reported and the proposed geometry described.