Minutes of the fifty-first meeting held on
Wednesday and Thursday, 21-22 March 2001
1. ALICE Addendum to Dimuon Forward Spectrometer TDR: F. Staley
2. Report from the Steering Group of the LHC Computing Review: S. Bethke
3. ATLAS Status Report: P. Jenni
The Director-General presented the LHC schedule as drawn up by a working group consisting of representatives from the LHC machine and the experiments. The main dates have the LHC machine closed and cooled down at the end of December 2005, with commissioning of the machine to be performed in January 2006. Single proton beam will be provided in February-March 2006, followed immediately by first proton collisions during a 4-week pilot run in April 2006. After a 3-month shutdown period, a 7-month proton physics run will commence in August 2006 with the aim of collecting at least 10 fb-1. A 6-week lead ion is scheduled commencing in March 2007.
4.1 REPORT FROM THE PISA WORKSHOP ON RPC
R. Santonico reported on the workshop held in Pisa on 18-20 January 2001 to discuss the BaBar RPC project status and plans for future RPC production. The presentation concentrated primarily on tests of the current generation of RPCs, which are planned for the new BaBar production, and for which the chambers are of the same type as those intended for the LHC. The main conclusions from the workshop are (a) the observed noise in RPCs depends strongly on the temperature, and (b) the noise is due to spontaneous discharges which are not uniformly distributed but are rather concentrated in particular positions inside the chamber. The degradation of the surface could be triggered by the mechanism whereby the noise produces an increase of the local temperature and therefore a decrease in the local resistivity. This in turn increases the noise rate thus creating a positive feedback loop, which in the extreme case produces a permanent damage to the chamber. Operating the chambers in streamer mode is more critical because the energy delivered per single discharge is much higher than in the avalanche mode. In order to overcome this positive feedback loop, the Bakelite plates have been coated in linseed oil in order to obtain a higher control of the surface properties before closing the chamber.
4.3 REPORT ON THE ATLAS RPCs
R. Santonico reported on the status of the ATLAS RPCs. Ageing tests in the Gamma Irradiation Facility (GIF) on chambers coated with a few microns of polymerised linseed oil show encouraging results. After the equivalent of operating 12 years in ATLAS, the module tested still exhibits a rate capability that is within the ATLAS requirements.
4.4 REPORT ON THE CMS RPCs
G. Iaselli presented the status of the CMS RPCs. He noted that the CMS RPC trigger was designed under the assumption that the single hit rate is dominated by neutrons. However, results from beam tests indicate that the noise from the chambers themselves is much higher than the neutron rate in the barrel, leading to an unacceptably high trigger rate. Current results from beam tests on chambers without the linseed oil coating show that the trigger rate can be kept to within the requirements but with little or no safety margin. Ways to improve the RPC working parameters are being considered ó coating the electrode surface with linseed oil, performing additional extensive R&D, and reviewing the construction procedure. CMS will evaluate these options in the coming months and will also inject in the discussion the improvements in the triggering.
4.5 REPORT ON THE LHCb RPCs
G. Carboni reported on the status of the LHCb RPC detector. Although tests indicate that coating the Bakelite with linseed oil reduces the noise and the dark current, thereby presenting less of a load on the trigger and minimizing the ageing, it does nonetheless complicate the chamber construction by making the manufacture more critical and introducing additional quality control factors. Therefore, LHCb has a preference for favouring a solution without requiring the use of linseed oil. Tests on prototype LHCb chambers will continue until the end of the year, at which point a decision on the construction method will be made.
Following an additional report, the LHCC will discuss the matter at its May 2001 session and present its conclusions and recommendations.
The referees also reviewed the status of the various CMS detectors and reported on the overall schedule and milestones. The LHCC considers that it is realistic to expect CMS to install a detector for the beginning of LHC operation in 2006, although detector installation is foreseen beyond the initial running. The presented lay-out of the initial detector will allow CMS to address satisfactorily the physics issues for Higgs and SUSY at the 10 fb-1 luminosity level.
Progress was reported on the performance of the tracking and these studies will continue. It was also shown that a concerted effort is being made by CMS to control the material budget of the Tracker.
Concerning the ECAL, preliminary results show improved robustness of the APDs to photon irradiation. Moreover, ingots can now be grown in Russia with a diameter large enough to cut two crystals per ingot, thus considerably improving the production rate.
The Committee has no major concerns. An ancillary document (LHCC 2001-009) records the overall assessment by the LHCC of the project at this time, thereby emphasizing some points which should be monitored in the future as the project progresses. This document also contains a list of agreed milestones for monitoring the progress of the project. The LHCC review of the TDR was not a detailed review of engineering or procurement readiness. These are anticipated in the planned progress of the project (Electronic Procurement Readiness Review PRR and the Electronics Systems Review ESR). Written reports of each PRR and ESR should be made available to the LHCC through its referees.
The LHCC recommends general approval of the CMS Level-1 Trigger Technical Design Report, pending a final cost evaluation. The LHCC considers the schedule given in the TDR and the list of milestones in the ancillary document to be appropriate. They will be used by the Committee to measure and regulate the future progress of the project.
Good overall progress was reported since the recent ALICE Comprehensive Review. The list of milestones presented at the Comprehensive Review has become the ALICE reference baseline, but some minor adjustments may arise after the new Technical Coordinator has completed his review. Some delays in the Muon Spectrometer, in the Trigger and ZDC were reported. Although not currently critical, the Collaboration is making efforts to recover the time. Moreover, in order to gauge better the progress of the TPC project, the referees have asked for a more detailed and complete report from the TPC group prior to the May session of the LHCC. Finally, it is expected that the milestones for the PHOS will be met as scheduled.
H. Dijkstra reported on the status of the Inner Tracking System. The reduction in the length of the two outer SSD layers and the two inner Pixel layers was reported. This reduces the overall cost of the ITS without affecting the physics performance and results in an overall matching of the ITS geometry to the acceptance of the TPC. Finally, good progress was reported on minimizing the thickness of the Pixel detectors and on the technology and yield of the bump-bonding process.
The referees also reported on their preliminary reactions to the Addendum to the Dimuon Forward Spectrometer Technical Design Report. The Addendum details the design modifications to the tracking chambers, and the resulting integration and overall performance issues. It also provides a status report of the associated detector sub-systems and introduces the conceptual design of the newly-proposed V0 detector, whose aim is to reject background events produced in the LHC machine during pp data-taking. Following further questions and discussions, the referees will make a full report at the next meeting of the LHCC.
Finally, plans are underway to organize a dedicated workshop on heavy-ion physics at the LHC, which will bring together theorists and experimentalists from the international heavy-ion community. The first session of the workshop will be held in the week 8-12 October 2001 and the entire multi-session forum is expected to last until mid-2002.
The referees reviewed the ATLAS general schedule. The LHCC considers that it is realistic to expect ATLAS to install a detector for the beginning of LHC operation in 2006, although detector installation is foreseen beyond the initial running. The presented lay-out of the initial detector will allow ATLAS to address satisfactorily the physics issues for Higgs and SUSY at the 10 fb-1 luminosity level.
Good progress was reported on the construction of the Muon Spectrometer - MDTs, CSCs, RPCs and TGCs. In addition, the referees reported on the Pixel detector. The failure of the DMILL process has resulted in a switch to DSM technology, resulting in a 15-month delay of the Pixel project. Such a delay does not allow installation of the Pixel detector inside the Inner Detector in 2004, and a new lay-out is required so that the Pixel detector installation can be performed independently of the Inner Detector in 2005. The LHCC noted that the design of the innermost B-layer is not changed. The LHCC takes note of the proposed modifications and asks to be informed of progress in the future.
The referees also reported on the status of the ATLAS Trigger/DAQ. Results from the studies of the trigger performance for various physics channels was presented, illustrating that the proposed system is robust. Further comparisons between the ATLAS and CMS trigger rates will be pursued. The new Trigger/DAQ organization has been put in place with the aim of preparing the TDR for submission in December 2002 rather than in December 2001. The LHC considers that the schedule for preparing the Trigger/DAQ TDR is tight but reasonable and remains appropriate for the timely completion of ATLAS. Finally, the LHCC asks for the detailed milestones on the hardware development and production.
The TDRs for the VELO and Muon detectors are on track for presentation to the LHCC at its session in July. For the former, the referees reported good overall progress for the mechanics and vacuum, the silicon technology, the material budget and the position of the off-detector electronics. Furthermore, good progress was reported on the design of the Muon detector.
The referees also reported on updates to the organization of the collaboration. A number of major countries have now signed the LHCb Memorandum of Understanding, representing a substantial part of the total cost.
Concerning the SPS, agreement was found between the NA57 heavy-ion experiment and CMS, so that the former could collect additional proton reference data at H4. The revised schedule includes also some further minor modifications.
The LHCC received the following documents: