Minutes of the LII Section meeting held on 19^th June 2006.

Present: G. Arduini, S. Aumon, G. Bellodi, E. Benedetto, O. Berrig, H. Braun, R. Bruce, M. Chanel, S. Gilardoni, H. Haseroth, M. Martini, S. Maury, J. Pasternak, F. Roncarolo, G. Smirnov.

Accelerator start-up status (G. Arduini)

PS and SPS are running for fixed target physics (with one fixed-target cycle per PS super-cycle) powered from the SPS compensator after the break-down of the PS rotating machine. The PS machine was restarted with beam in this configuration on Tue 6^th June and the SPS was restarted with beam on 9^th June when the second SPS compensator available. No major problem was encountered to establish circulating beam. A significant time was spent in debugging the software. Voluntary misalignments have been applied to the machine in order to improve the high energy orbit.

The rotating machine will be restarted in the middle of the week.

Orbit error implementation in ICOSIM (H. Braun) (slides).

Orbit bumps have been implemented in ICOSIM in order to include the effect of the separation bumps and closed orbit distortion. The detailed distribution of the losses in the quadrupoles needs still to be implemented. G. Bellodi will perform a detailed study of the effect of the closed-orbit distortion on the beam loss distribution.

Electromagnetic interactions for channeled ions (G. Smirnov) (slides)

G. Smirnov presented the results of the estimation of the probability of electromagnetic interactions of channeled ions at 2.76 TeV/u/c. This estimation is based on a "continuous potential" model which accurately describes channeling. No significant electromagnetic interaction is expected for the channeled beam.

Status of the LINAC4 studies (M. Martini) (slides)

M. Martini presented the results of the ACCSIM simulations for 160 MeV H- injection into the PSBooster including dipolar and quadrupolar errors provided by C. Carli. The resulting emittances are larger than those obtained in the absence of errors right at injection. This is very likely the result of the oscillations at injection. The injection oscillations should be corrected in the simulation. The present proton injection in the PSBooster at 50 MeV has been also simulated with no magnetic errors and for intensities approximately 40-50 % larger than those normally injected in the PSB. The observed losses (~55 %) are slightly larger than those observed in operation (~45%). This difference might be related to the larger intensity considered in the simulations. It was suggested to repeat the simulation with parameters as close as possible to the PSB operational conditions for high intensity beams.

Status of the gamma jump study in the PS (S. Aumon) (slides)

 The maximum horizontal beta function at straight section 63 can be reduced by independently powering the two branches of the gamma jump doublets and triplets and by "unbalancing" the currents in the two branches. The present powering scheme does not allow that but this solution could be considered in the frame of the renovation of the power supplies for the gamma jump quadrupoles. Measurements performed with beam at transition have evidenced significant orbit horizontal orbit distortions mainly depending from the currents in the doublets. It was noted that the observed variation could be related to an energy offset and in that case the observed variations should be compatible with the dispersion pattern during transition. 

Next meeting and tentative agenda

Monday, 14^th August 2006 at 09:00 in room 354-1-001

General information (G. Arduini)

Gamma jump in the PS: final results (S. Aumon)

Gamma jump in the PS: measurements performed and results with beam (S. Gilardoni)