Minutes of the LIS Section meeting held on 1^st August 2011

Present: G. Arduini, C. Carli, A. Lachaize, Y. Papaphilippou

General Information (Gianluigi)

Gianluigi reminded the deadline for the submission of the IPAC11 papers to Delphine or her replacement with copy to him: 22^nd of August. Delphine will be absent from 12/8 to 4/9 included but her replacement will be able to read her e-mails.

A staff child (M. Hourican) is working ]to scan documents that are not available in CDS and collect them in EDMS. Whoever has documents that can be of interest for the group and are not available in electronic format should give them to Delphine. The scanned documents are available at:

https://edms.cern.ch/nav/P:CERN-0000077386:V0/P:CERN-0000091358:V0/TAB3

A. Parfenova, GSI, would like to apply for a fellowship. Christian asked to see her CV. Gianluigi will send it to him. Action: Gianluigi

There will be a new round of COFUND fellowship for the selection committees in November 2011 and May 2012.

3 posts have been submitted to HR and they will be published soon: 2 physicists positions (optics and PSB Injectors) and 1 technical engineer for SU.

A Sector retreat on 4/8 to discuss the flexibility posts.

 Outcome of Mini-Chamonix: The advantages and drawbacks of increasing the luminosity by pushing on bunch intensity, transverse emittance, beta*, and bunch spacing have been discussed. The first two parameters appeared more advantageous; squeezing beta* to 1 m is an interesting possibility, but was put on hold for the time being; finally, the overheads of switching to 25 ns advised to exclude it for 2011.

LHC: The injectors are providing 50 ns beam with double batch injection. Now we running with minimum emittance form the injectors and ~2 micrometer emittance in collision or smaller. 2x10³³ cm^-2 s^-1 has been achieved with bunch populations of ~1.2x10¹¹ p/bunch. The integrated luminosity rate is  not increasing significantly as fills tend to be shorter due to a series of problems (some of them related to intensity - SEU and UFOs, some other not related to intensity) leading to poorer machine availability.

NuFact 2011 has started today for the whole week at CERN and University of Geneva.

Gianluigi informed the meeting that he will be absent from 15 to 19/8 (included) for a duty trip and holidays.

Round table (all)

Antoine : Measurement of the closure of the slow bump 16 have continued. It seem that the bump is closed for the core and not for the islands. Furthermore the non-closure of the islands bump depends on the preceding cycle. The bump is closed when the preceding cycle is of the TOF type. Gianluigi asked whether different preceding cycles having the same extraction energy (e.g. LHCPROBE and LHC50ns) produce the same effect. Antoine replied that this has not been tested he also mentioned that unless the reason for that is understood different settings could be envisaged to close the bump according to the type of preceding cycle.

Yannis mentioned that there is quite some pressure to get POPS operating again, in order to conduct test before the PO team go on holidays.

X-X' analysis application: Yannis asked for feedback on any required modification of the application. He will ask Simone.

Christian:

LEIR is starting-up with beam. The beam is in the first art of the injection line but there is a problem with one of the magnets in the transfer line (interlock from a thermoswitch).

Vivien is running ORBIT simulations of the multi-turn injection in the PS Booster for the present injection with LINAC2 at 50 MeV to benchmark the code with the experimental data and in view of studying the multi-turn injection of a proton beam at 50 MeV as it could be delivered by LINAC4 in case of a failure of LINAC2. Elias has suggested a possible option of injecting 3 batches in the PS-Booster that could compensate for the expected reduction in performance in such a scenario.

LINAC4 to PSB transfer line: the layout is being frozen.

Christian mentioned that it will not be possible to use the CERN standard vacuum chambers (100 mm diameter) for the LINAC4 quadrupoles because they do not fit in their aperture. Gianluigi asked whether it is still possible to review the design of the magnets. Christian replied that this is possible but this would further increase the requirements on the specifications for the power supplies which are already marginal. Special vacuum chambers will have to be built. Gianluigi asked whether this would entail delays but Christian replied that this should not be the case.

Gianluigi reminded Christian that he should provide Simone with measurements and simulation of the emittance of the various beams presently delivered by the PSB as a function of intensity (Action: Christian).

Gianluigi asked what is the status of the 2 GeV extraction from the PS as a test for a possible low energy extraction of an ion beam to the East Hall. Christian replied that no progress has been done. Antoine added that the 2 GeV non-linear model of the PS is now available and the simulation of the slow-extraction could be easily done.

Yannis:

Yannis mentioned that from September he will start as SPS supervisor and he will stop PS supervision.

Recently it has been discovered that the LHC beams were not tuned correctly in the PS and the chromaticity was negative at extraction. For the moment only a couple of operators know (and no other) know how to use the application for the tune and chromaticity correction.

Last Wednesday the settings of the PSB to SPS transfer line were corrupted and the line had to be re-steered. This could be a controls issue.

Hannes has progressed with the Q20 studies with tune scans to determine the resonance line in the tune diagram. As already observed in the past the chromaticity is varying along the injection plateau as a result of the eddy currents flowing in the vacuum chambers. Furthermore the non-linear magnetic field components in the main magnets at injection depends significantly on the magnetic history. Measurements of the chromaticity are being performed all along the injection plateau. Gianluigi suggested to see with the RF colleagues whether they could provide tools to modulate the RF frequency at injection. Gianluigi suggested also to conduct non-linear resonance terms measurements. Yannis said that this could be done in combination with the tune scans.

High intensity single bunch beams with up to 4.2 x 10¹¹ p could be injected with the Q20 optics with no sign of blowup but losses are observed when the fractional vertical tune is kept below 0.2. When increasing the bunch population an instability has been observed between 3 and 3.5x10¹¹ when the chromaticity is close to 0.1. This could be an indication of a coupling of modes followed by decoupling at higher bunch population.

Gianluigi asked whether PS2 CDR has been published. Yannis replied in the negative.

Gersende (by e-mail as she was at NuFact 2011): On the Neutrino Factory side she reported that she is very happy with the work that Anton Akimov (child from the CERN personal) did. He completed the tedious task of comparing for the Neutrino Front end, the parameters from our two simulations ICOOL and G4BL together with the content of the IDR report. This was essential to correct the inaccuracies in the IDR, align ICOOL and G4BL simulations and prepare the engineering/costing. He also looked into M. Aiba MADX simulations and listed the accumulator and compressor rings parameters of the proton driver, with the same aim, to bring those parameters toward a engineering/costing estimate.   Evgenia Alexandri (our summer student) is getting on track with the 44-88 MHz lattice and it is hoped to have the simulations ready for the IPAC conference.

Next meeting

Monday, 29^th August 2011 at 14:00 in room 6-R-012

Agenda to be defined

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