Minutes of the LIS Section meeting held on 29^th June 2009

Present: S. Aumon, G. Arduini, H. Bartosik, O. Berrig, M. Chanel, C. Carli, S. Gilardoni, M. Martini, EY. Papaphilippou, D. Quatraro

General Information (Gianluigi)

• Simon Baird is looking into a second round of consolidation needs. Possible proposals for items to be included (left out in the previous campaign) and a couple of lines of justification (why, urgency, risks if not done) should be sent to Gianluigi by tomorrow Tuesday.
• No run through Christmas. CERN will be closed from19/12/2009  to 3/1/2010
• A practical training on the use of the Bio-cells is now available. It is very well organized and it will become mandatory for LHC and SPS access. Interested people should inform Gianluigi.

• Publishing of documents at the sector level has been reviewed. Gianluigi will circulate the document summarizing that.

• A new Machine Advisory Committee will be set-up to cover the issues related to the commissioning, operation, performance of the LHC and its injectors as well as their upgrade.

• Frank Schmidt is the Departmental representative (together with P. Charrue) for the issues related to central software support from IT. Any issue related to central IT support should be transmitted to him.

LHC (Gianluigi)

As announced by the DG vacuum leaks have been detected in 2 cold sectors (23 and 81). The repair will imply warming up a section for these sectors. For sector 23 most of the HW Commissioning will have to be repeated. The measurements of the copper stabilizer continuity in the interconnects is almost complete. A summary of the measurements will be presented at the next LMC and should allow defining the maximum energy to which the LHC can be run safely during the next run. The next sector available for HWC will be sector 12 in the second half of August.

Round-table (all)

PS (Sandra, Simone, Yannis)

Work has continued on the long LHC cycle (Yannis) for operation of the PS without rotating machine. The remaining timing issues for the operation of the longitudinal gymnastics have been fixed and an LHC beam with 25 ns spacing could be produced with half nominal bunch intensity. Work should be done in the optimization of the transition crossing and of the working point. The corresponding study for the CNGS beam has started but the cycle needs to be re-design to take into account properly all the constraints imposed by the operation without rotating machine. A presentation has been given on the subject to the MSWG.

Simone asking for the possibility to inject at lower energy in the SPS and to suppress the splitting in order to reduce the cycle length. Gianluigi replied that given the limit in vertical aperture in the SPS injection at lower energy will result in larger losses. Concerning the suppression of the splitting and of the corresponding plateau Yannis replied that the reduction is not sufficient to compensate for the longer ramp time.

Non-reproducibility of the wire scanner profile data. In the vertical plane there is an inconsistency in the measurements from wire scanners and SEM wires in the TT2 line. This is different from what observed during a campaign of measurements performed approximately 1 month ago. In the mean time the application has been changed. Same observation was done in PSB. After the meeting: it seems that the reason for the discrepancy in the PS has been understood. The wrong fitting algorithm was used by the operators in TT2.

The Q-meter is more stable. A user-dependent offset in the timing of measurement of tune has been observed together with a jitter. This affects the measurements required for MTE set-up and in particular the measurement of tune variation during extraction bump excitation. This problem has been fixed after the meeting.

Injection studies will be performed during the next dedicated MD on Wednesday. A mechanical problem has been fixed by BI but no test was done to verify that. Gianluigi suggested to verify that as soon as possible and before the MD.

The radial beam control with a new set of pick-ups as proposed by Sandra and Simone has been tested. Better control of the radial position has been obtained. Gianluigi suggested to implement this change in all operational beams after detailed verification of the data.

MTE (Simone)

Work is ongoing in the optimization of the working point. Measurement and correction of the working point is still taking a lot of time due to lack of tools to correct tune and chromaticity in 5-current mode of operation. A dependence of the capture on the longitudinal properties of the beam has been observed. A core with large emittance is observed when the beam is bunched. Very likely this is due to the fact that the chromaticity becomes negative during the flat-top and the beam becomes unstable. The beam is not getting unstable when it is debunched but in this case the sharing among the islands and the core is unequal. Correction of the chromaticity will be done and the resonance will be crossed starting from higher tunes. According to simulations performed by Massimo Giovannozzi this should provide a more uniform sharing.

PS2 (Hannes, Yannis)

New straight section design has been presented based on doublets. This allows reducing the  space required and will provide more space for the dispersion suppressors minimizing the beta and dispersion excursions and the gradient requirements on some of the quadrupoles.

PSBooster (Diego)

Additional measurements have been taken by Diego to characterize the instability observed in the PS Booster at low energy and to determine the impedance model of the machine. Stability issues. Time of the instability depends on tune. Chromaticity measurements. Data need to be analyzed in detail. Simulations being done to try to reproduce the measured data.

LEIR and ions (Christian, Michel Chanel)

LEIR started well in spite of the difficulties with controls mainly. A low intensity is delivered from LINAC3. The injection efficiency should be also improved. It is clear that with the present source operation to early intensity is marginal.

Ions have been delivered to the PS since last Wednesday. The beam lifetime was less than 2 s before starting sublimation to improve the vacuum. After a sublimation during the week-end the lifetime was larger than 4 s. This is acceptable for the ion commissioning.

Plan to set-up the acceleration this week in the PS.

LINAC4 injection into the PSBooster (Christian, Michel Martini)

LINAC4: ORBIT simulations have been pursued beyond the first 10 ms after injection. In the second interval of 10 ms a blow-up is observed for the ultimate LHC beam in the horizontal plane. A simulation without space charge does not reveal any blow-up. The injection foil and apertures in the injection region have been added. Next steps:

• verification of the dependence of the blow-up as a function of the working point
• verification of the dependence of the blow-up on the number of macroparticles (the present simulation has been done with 100000 macroparticles.

Gianluigi asked whether the simulation has been performed with D=0 at the injection point as this is the baseline. Michel Martini and Christian do not recall what was the condition.

There are still problems in running long jobs (longer than 24 hours on lxclic. Christian and Michel are going to investigate that. Gianluigi encouraged Christian and Michel to use the new IT supported cluster in order to determine the potential problems and to verify whether the cluster is sufficiently powerful to conduct detailed simulations in a realistic time. Action: Christian and Michel Martini.

Optics repository (Olav)

The new LHC optics produced by Masamitsu is being put in the repository. Olav is going to work on that with Masamitsu before he leaves. Pre-squeeze and squeeze combined files have been also produced.

Gianluigi encouraged Olav to complete the note on the FT61 line (initial conditions) next week. Action: Olav

Next meeting

Monday, 10^th August 2009 at 14:00 in room 354-1-001

Agenda to be defined.

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