Minutes of the LIS Section meeting held on 5^th May 2008

Present: M.Aiba, G. Arduini, S. Aumon, J. Barranco, E. Benedetto, C. Carli, M. Chanel, A. Franchi, S. Gilardoni, M. Martini, E. Métral, B. Mikulec, Y. Papaphilippou, D. Quatraro, G. Rumolo,

General Information (G. Arduini)

A Group Meeting will take place on 15^th May.

A mailing list has been created to distribute the information about the machine status by the supervisors within the section (ab-dep-abp-lis@cern.ch).

The deadline for the fellow requests is tomorrow 6^th May.

LHC HWC is progressing well. Training quenches for the main bends in Sector 5-6 have started.

PSB realignment (G. Rumolo) - slides

This is a follow-up of the presentation given at the LIS meeting on 11/2/2008.

Since then survey data of the PSB beam position monitors (BPM) have been made available by TS/SU (T. Dobers) and the orbit data taken in 2007 have been re-analyzed after correction for the measured BPM misalignments. The resulting new scheme resulted in a further reduction of the expected peak-to-peak orbit by more than 1 mm in the vertical plane. In total 9 quadrupoles have been re-aligned before the end of the shut-down. After this first correction a clear improvement has been observed in the vertical plane (reduction by a factor 3 of the r.m.s. and peak-to-peak orbit distortion) while in the horizontal plane the improvement was less spectacular. A second iteration has been performed during the start-up with beam (2 quadrupoles) and resulted in a reduction of the peak-to-peak horizontal orbit distortion by a factor 2. The improved orbit has resulted in a reduction of the losses and very high intensities could be achieved in few days. The losses in Ring 3 have disappeared and ring 3 is likely the ring with best performance as it was some years ago.

A general re-alignment of the PSBooster will be likely required for next year. Gianluigi pointed out that this should be requested well in advance. Giovanni to follow that up with OP.

Round table (all)

Elias

The data of the simulations performed for the impedance of the 800 MHz Travelling Wave cavities have been sent by B. Spataro to Elias.

Rama has started to work on the analysis of the effect of a localized impedance on the phase advance dependence on intensity with HEADTAIL. HEADTAIL has been upgraded to allow this kind of analysis.

Simone

The orbit acquisition in the PS does not work along the ramp. It seems that this is the consequence of a modification of the amplifier stage. As a result of that the signals are saturating and large offsets are measured. J. Belleman is working on that but for the moment there is not yet a solution proposed. In these conditions it will be very difficult to work on optimizing transition.

The measurement of the matrices for the tune and chromaticity correction is also not possible as it is not possible to measure the radial position reliably.

The ripple observed in the pole-face windings at 14 GeV/c last year has been corrected.

Christian / Masamitsu / Michel Martini for LINAC4

Studies are ongoing for the optimization of the injection in collaboration with B. Goddard

Christian is in contact with F. Ostiguy for the ORBIT simulations and in general for the optimization of the distributions to minimize numerical artifacts.

Michel Martini has started to work on the ORBIT simulations of the experiments conducted in the PS-Booster in 2007 on a 160 MeV plateau.

Andrea

Andrea is working at the preparation of the knobs for the bump 16 in its new configuration with independent power supplies for the MTE.

Elias / Javier / Yannis  for PS2

Preparation of the internal review for the PS2 (transition crossing, negative momentum compaction lattice, aperture, loss maps and collimation). Elias will provide the energy dependence of the rise time for the longitudinal negative mass and vertical microwave instability to determine whether crossing transition at higher energy might be more beneficial. On the other hand Elias pointed out that increasing the transition energy might imply lowering the threshold for the vertical e-cloud instability if no measure is taken to suppress the electron cloud buiild-up.

Olav

Olav mentioned that the aperture and MADX models for the PSB, PS and SPS machines have been updated to take into account the modifications occurred during the shut-down. The back-leg windings have been added to the PS model.

Sandra and Simone for the PS gamma jump

Sandra has simulated the effect of unbalancing the currents in the pair of doublets as they are cabled now (the cabling was not performed as requested in order to keep backward compatibility with the old power supplies for this year) but no benefit is expected. For this year we will run with equal currents on the doublets and the specifications for next year will be described in a note ==> Simone with PO/OP

Next meeting

Monday, 19^th May 2008 at 10:30 in room 354-1-001

Agenda

General Information (Gianluigi)

LINAC4 to PSB beam dynamics studies: status (Christian)

A.O.B.

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