Minutes of the LIS Section meeting held on 19th May 2008

Present: M.Aiba, G. Arduini, G. Bellodi, E. Benedetto, O. Berrig, C. Carli, M. Chanel, S. Gilardoni, M. Martini, E. Métral, B. Mikulec, Y. Papaphilippou, D. Quatraro, G. Rumolo, B. Salvant

General Information (G. Arduini)

There have been some requests for participation to HB2008. Participation will have to be limited to few persons because of budget constraints. For the moment people receiving invitations should reply by saying that a final confirmation of their participation depends on the final approval of the group leader.

LHC: HW Commissioning for sector 7-8 started

Training quenches in Sector 5-6 are ongoing.

Status of the LINAC4 studies (C. Carli) - slides

Christian illustrated the scheme for the H- injection in the PSBooster. H- injection is also implemented in the Booster at FNAL but they have no dump and they have no injection bump for painting. Painting is obtained only by a rapid decrease of the injection chicane. Christian and Michel Chanel are looking into a possible different proposal for the injection for the LINAC4 into PSB in which the current in the dipoles of injection chicane could be kept constant and the injection bump should be larger. In that case collimators intercepting particles at large amplitude are required.

Energy deposition and heating of the stripping foil is one of the major issues for H- injection for that reason extensive simulations have been conducted mainly by Masamitsu. He has developed a new routine (now included in the ORBIT official release) for the estimation of the temperature reached by the foil taking into account multiple scattering and nuclear interactions. The thermal load due to stripped electrons has not been included. An electron catcher is installed at SNS.

Simulations seem to indicate that there is no significant dependence in performance on the value of the dispersion at the end of the injection line. The baseline will be to have the dispersion vanishing at injection in the PSB but the design of the line is such to allow tuning it and possibly matching it at injection. Twiss parameters at the end of the injection line need still to be defined although the choice will be mainly driven by the need of minimizing the vertical size at the distributor and by the need of focussing at the stripping foil. Vertical mis-steering will be applied to provide some painting in the vertical plane. This will lead to a ring distribution in phase space. Christian asked whether this could reduce Landau damping ==> Giovanni, Elias

 The dependence of the emittance evolution as a function of the number of macro-particles has been studied by Masamitsu a dependence on the number of particles is still observed above 200000 particles in particular in the vertical plane. A simulation with up to 917000 particles has been performed still showing a smaller emittance blow-up.

Michel Martini has started a series of ORBIT simulations (with 200000 macro-particles) to reproduce the experiments performed by Michel Chanel in 2007. The preliminary results seem to indicate a fair agreement with the measured data. This was not the case with ACCSIM (where the number of macro-particles was limited to 100000). It takes approximately 1 week to simulate 30000 turns (~30 ms) with 200000 macro-particles. ORBIT runs are performed with 10 processors in parallel. The simulation programme crashes when a large number of processors are used. This needs to be investigated.

Diego asked whether the space charge model in ORBIT includes boundary conditions. Christian replied that the runs performed so far do assume free space but that routines with boundary conditions included exist.

Christian added that the effect of imperfections should be included in the simulations (e.g. the effect of the injection chicane).

Round table (all)

Elias

First machine studies have been conducted to perform controlled transverse emittance blow-up in the SPS to tailor the emittance of the LHC beam to the LHC needs (particular for low intensity. For the moment the wire scanners are not working. BI are working on that.

A discussion has taken place with D. Smekens (AT/MCS) to see whether West Area splitters can be used as spares for the North Area splitters as presently only one spare is available. The West Area splitter have a larger aperture. D. Smekens will provide the magnetic properties of these magnets in order to evaluate the impact of such replacement.

The voluntary misalignment of some quadrupoles (2 horizontal and 4 vertical) have been performed.

The impedance simulation campaign for the SPS is progressing in collaboration with B. Spataro (INFN-LNF) - slides

Elias has provided the formulas for the dependence of the threshold and rise-time of the longitudinal transverse and microwave instabilities on the gamma transition - slides

Olav

Olav is in contact with F. Schmidt and E. Forrest to understand the observed differences between MADX and PTC.

Next meeting

Monday, 2nd June 2008 at 10:30 in room 354-1-001

Agenda

General Information (Gianluigi)

PSB impedance model: what do we know (Michel Chanel)

A.O.B.

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