A Macpherson: 2008-07-14

LHCCWG # 50 Minutes

8 July2008

Present: R Alemany Fernandez, G Arduini, R Assmann, R Bailey, H Burkhardt, M Dankor, B Dehning, S Fartoukh, M Giovannozzi, B Holzer, L Jensen, J Jowett, G Kruk, M Lamont, R Lindner, A Macpherson, D Micallet, D Nisbet, L Ponce, R Schmidt, J Uythoven, W Venturini Delsolaro

Results from tests with B-field in LHCb: R Linder

· LHCb reported on the powering of their magnet, which primarily checked

o Magnet Control System/ Magnet Safety System

o Verification of isolation

o Beam Dump (fast ramp down)

o Movement of their RICH 1: previous switch on of the magnet caused a displacement of 1.7 mm.

o Measurement of magnetic field and symmetry between positive and negative B-field.

· Powering results that the B-field was “sufficiently good”

o The symmetry was measured to the level of (B- - B+) <0.0001 T at ~1.13 T

o ‘Demagnetizing’ cycle does not improve the symmetry of neg/pos B-field significantly, so is not to be done.

o A B field ripple of ~5 x 10^-5 in the nominal B –field with a period of ~40 minutes was found to be induced by a variation in the cooling water temperature of the dipole cooling circuit, but the effect is negligible for physics

o Changing of the B-field polarity can be done without running through a sequence.

o Improved detector fixation was been verified.

o The RICH2 Hybrid Photon Detectors (HPD) were checked for image distortion under magnet operation, and are now commissioned with B-field.

• R Bailey asked if all tests had now finished. Response: Yes, up to a final check when all LHCb detectors are in and operating.
• B Holzer asked if the control of the 3 compensator magnets associated with the dipole have been tested. Response: they have been validated for operation and the synchronization of the controls/ interlocking has been checked.

Warm Magnets in Point 3: M. Giovannozzi

• The issue is that due to high circuit resistance, some magnets in IR3 are limited below the nominal or ultimate performance.
• The proposed solution is to install additional cables in parallel to those already installed. The presentation identified circuits for which this additional cable is needed.
• Of the 9 circuits involved, only the RQT4.R3 and RQT5.R3 have an I_max < I_nominal. For RQT4 Imax/Inominal = 322/600 and for RQT5 it is 454/600
• In addition to RQT4/5 it has been offered that RCBWH5.R3B1 and RCBWV5.R3B2 circuits also be modified as Imax/Inom ~520/500
• The cable installation is not mandatory before the 2008 run.
• G. Arduini asked if the cable installation could be done before startup, and R Schmidt that the present planning had the cables for the 2 quads being installed during week 30.

BLM Data Transfer to Databases: B Dehning

• Bernd described the process of the BLM data transfer. This involves the following steps:
• Generation of data in threshold comparator and combiner
• Packaging of data by VME crate sent to concentrator
• Concentrator reception of data, computation, filtering, packaging and sending of data to clients (measurement DB, displays, collimation, …)
• Measurement to Logging database, filtering (one value every 60 s and logging if value are over threshold)
• Unfortunately with the present system only ~2000 BLMs are useable at any one time, so that for 2008, some form of data reduction is needed.
• It was stated that such a reduction in the transmitted data should only be considered as temporary, as database improvements are expected after 2008.
• The initial proposal put forward by Bernd was that only 6 of the 12 running be transmitted, and that the transmission rate be reduced to 0.5Hz sums
• R Assmann stated that this proposal was unacceptable as these reductions would significantly increase the time for collimator commissioning
• After some discussion, a new proposal was agreed upon and requires the following:
• The BLM data is pushed off the front end at a rate of 1 Hz, and this data can be provided to the collimator system at 1 Hz for the feedback during collimator commissioning.
• BLM data is pushed to the logging data base at a rate of 0.5 Hz
• The filtering of the data is not done at the device level but instead, should be done at the database level. ie the data arrives at the concentrator at a 1Hz rate, but is filtered before logging.
• It was not clarified at the end of the discussion if the number of transmitted running sums would be reduced from 12 to 6.

S56 tracking performance between RQF.A56, RQD.A56 and RB.A56. David Nisbet

• The presentation can be found at https://edms.cern.ch/document/933361/1
• Tracking between main circuits was found to give an I_ref – I_Act =2.3ppm
• The global postmortem timing event was used to generate a synchronized tracking test that could work across multiple sectors
• M. Lamont pointed out that it might be better to use a selective trigger once more of the machine is available, as the global postmortem trigger links to many systems.
• G. Arduini asked if comparing a linear interpolation of the converter steps to the I_measured had also done the measurements.
• Response: At present such a refinement had not been done, but the data could be made available.
• S Fartoukh asked if I_QF/I_MB and I_QD/I_MB had been determined, as this would give a good estimate of b2/b1 to the few ppm level and could be used to estimate the quality of a ramp, as variations would indicate tune shifts. This had not yet been looked at.

ICC report: R Bailey

• Roger reported the main points from the ICC held on the 4^th of July,
• L.Evans informed the committee that the target date for closure of the detectors and the experimental caverns is now the end of the first week of August
• A cleanup campaign for the tunnel that is needed before beam is injected. The clean schedule presented went from the present through to the 28^th of August.
• A version of the HWC schedule (dated July 2^nd) was shown that had HWC finishing at the end of week 35, and involved powering in up to 4 sectors at once.
• DSO tests are mandatory before injection of first beam
• These tests can be broken down into three categories
• Intrusion into the machine when in “beam” mode
• Éléments importantes de Sécurité (EiS) going unsafe when in “access” mode
• Auxiliary functions (Patrols, passage through PAD/MAD, Mode changes, connection to BIC and LBDS, etc)
• The strategy and timing of the DSO tests is still being decided, but is expected to have a significant impact on accessibility of the machine and experimental caverns
• A proposal for the DSO tests has to be discussed both with the machine and the experiments.
• At present that initially proposed date for the DSO tests is week 31, and would take ~ six 8-hr evening shifts.
• It was commented that in the planning shown there didn’t seem to be sufficient allocation for cold checkout. Roger noted this, but commented that the end game planning was difficult to finalize. J Uythoven also noted that time needs to be reserved for Machine protection commissioning.