Minutes of the ALICE Technical Board, CERN

Transcription

1 ALICE MIN TB_F-2012 Date Minutes of the ALICE Technical Board, CERN Minutes The draft minutes of the June 2012 TB were approved. No minutes were taken of the July, August or September 2012 meetings. 2. P2 issues and LS1 preparations A. Tauro, presented this topic, see annexe 2. TS3: 24 th 28 th September Several detectors took advantage of this stop to repair, control and upgrade their systems: Experiment status during Xmas Underground access will be possible in weeks 51 and 52 until 28 th December. 1

2 Very few interventions are expected and Technical Coordination must be informed. For running conditions see G. Scioli s presentation below. Status of gas and cooling systems during Xmas Diesel Test on 18 th December This test will interrupt power for 2 minutes from 07:00 07:02 and will affect: all wall outlets; all non-ups outlets in the ACR (so essentially all WRs); outlets SXL2, offices and barracks; non-ups power for the detector cooling plants; power to all gas systems. LS1 plan Starts 11 Feb LHC commissioning with beam from December 2014 until beginning of April Schedule mostly unchanged since last TB. ALICE plans for LS1 2

3 In addition, many other projects will be carried out in LS1including: Electrical supply and systems: AUG emergency stop test: diesel test; 400 kv test; UPS upgrade CV maintenance and upgrade: cooling towers and plants; L3 ventilation upgrade; chilled water and demineralised water upgrade this will cause several interruptions; please see presentation for all the details. DCal status and update The support beams, delivered and tested in November 2011, will receive the DCal ribs for a full load test and survey next week. Yannick and Samuel have developed a special pushing tool for the insertion of the Super Modules. ITS ventilator update Significant improvements inside SSD. 3

4 Present settings will be kept for rest of 2012/ 13 run. V0-A and FMD1 V0-A will be repaired during LS1 due to the ageing of the Photo Multiplier Tubes. The decision has to be made whether to do this inside the MiniFrame or in SX2. Taking advantage of the removal of V0-1 a small leak on FMD1 will be fixed. Other matters: Perturbations at P2 o Relatively stable operation for ALICE o Electrical perturbations due to thunderstorms phase losses trigger beam dumps o 18 kv compensator filter 2 trips o 1 Solenoid trip o 7 Dipole trips o 21 st September 18 kv transformers trip cause still unknown Replacement of SXL2 doors to be installed next week 3. Report from run coordination A. Kurepin, RC period co-ordinator, gave this presentation, see annexe 1. LHC: In September, stable beam time was below average for this year. This can partly be attributed to TS3 which took place in week 39 as well as several technical malfunctions during the period: vacuum, cryo and electrical faults had a negative effect on the machine s efficiency. Week 40 showed improved efficiency with 46.7% Stable Beam time as compared with the average total efficiency of 35.8%: 4

5 Bunch intensity remained stable over the period but luminosity performance in ALICE increased in weeks 39 and 40. ALICE integrated luminosity increased significantly in week 40 due to an increased satellite population scenario from BE (S. Hancock). ALICE main activities in September: p-pb pilot: th September: Data collection: 5

6 The pilot fill was very successful with sufficient good quality data taken. One of the first p-pb collisions TS3 access details see A. Tauro s presentation above for details Issues following power cut on 21 st September DAQ upgrade during Machine Development: 6

7 This was an electrical network upgrade to enhance protocol between ECS and CTP at Start Of Run. CTP upgrade during Machine Development: This included the following items: ECS command: LOAD_PARTITION replaced by INIT_PARTITION Synchronous downscaling BMCL mask isolated bunches as a subset of B-bunches Past/ Future protection +/- 3 Bunch Crossings around the interaction Detectors not in Readout PMD: keep in supersafe and not running until next TS at least ZDC is out for PHYSICS_1 and in for Technical runs End of Run Reasons Conclusions The Pilot run for p-pb was a great success. This can be put down to great teamwork and Gilda s brilliant coordination skills. New satellite scenario and successful fills by LHC increased ALICE luminosity to 10 Hz/ub. The technical stop gave time to subsystem experts to solve problems and make improvements. 4. High Lumi p-p run and p-a preparations The Run Coordinator, G. Scioli, gave this presentation. See annexe 3. High Lumi p-p run: Increasing Luminosity There are 2 possibilities for increasing luminosity in ALICE: 7

8 Increase the satellite population by a factor of 6-8 to obtain a leveled luminosity of 5 Hz/ub. Use a main-main collision scheme Before resorting to main-main collisions it was agreed to try increasing the satellite population as above. Present data taking strategy In order to take advantage of the higher luminosity by increased satellite population, we need to adapt the data taking strategy so that we start data taking at higher rates. The detectors concerned have agreed to this as described below: p-pb run preparation The ALICE plan and subsystem conditions at the end of 2012 and the beginning of 2013 are shown in the slide below: 8

9 Status of detectors during TS4 and the Xmas break and type of data taking: Gas systems: 9

10 Shifts during p-pb run All the shift roles have been disabled in the SMS for this period. The shift blocks concerned will be assigned to expert shifters. System Run Coordinators for the General Systems and the RC for the Shift leaders will send an to a restricted group of experts to agree on the assignment of shift blocks. The decision to have shifts for the detectors during the p-pb period will be finalized in the near future. 5. TPC status operating at nominal gain and high intensity This presentation was given by C. Lippmann, see annexe 4. Background In 2010, the TPC experienced frequent chamber trips causing damage to the Front End Electronics. This was due to the discharge of energy from the HV capacitors into the FEE. The capacitors were subsequently removed in the 2010/ 11winter stop. In 2011 there was no more damage to the FEEs. However, there were still frequent chamber trips as collision rates increased from 10 khz to 100 khz. In 2012 new power supplies were installed. ROC HV PS Their new features included an independent HV source for each channel and the possibility of tuning the trip sensitivity by varying the current and the delay on the trip. There were a few issues during commissioning but ISEG, the suppliers were very responsive to solving the problems. During beam operation the trip limits have been successively raised. The result is an acceptable trip rate of a few per week especially in view of the increasing collision rates that have gone from a V0tot rate of <100 up to 400 khz. There was a very calm 4 week period just before TS3 at the end of September. The slide below is an example of this smooth running. 10

11 HV instabilities still occur. Occasionally, during periods of up to 2 hours, several chambers trip or experience high currents. Voltage drops or trips in the Field Cage can accompany this. The situation calms after a while and one wonders if this could not have a connection with beam instabilities. Fighting ROCs Other HV issues OROCs A05 and C06 can show high and rather constant currents. This problem disappears when the voltage is lowered by 10v to 40v.This problem is due to floating anode wires: the segments concerned will be given separate HV channels during LS1. TPC gain On August 8 th, the IROC HV was put back to nominal gain and there has been no change in the frequency of trips. As far as data quality is concerned there are no issues at high rates: Field cage The FC can trip during fills that have bad background conditions Over the last few months, thev0tot rate for ramping the FC to full voltage has been progressively raised to 550 khz. Since the last TS3 (end September), the FC tripped 3 times at V0tot rates of between 400 and 500 khz no such problems before TS3. There have been no trips since oxygen was added to the carbon dioxide volumes on October 6 th. 11

12 Pause_and_configure The TPC FEE is automatically configured during a run if one of 3 error conditions is detected. This procedure was initiated on August 23 rd. It requires no intervention from the shifter and takes 2minutes without stopping the run. SYNC event synchronizes all links even with backpressure. The procedure works very well. After LS1, it will be further improved by including the reconfiguration of the FEE if the readout gets stuck. End Of Run reasons Summary The new HV PS have improved stable running. TPC now runs at higher rates V0tot = 400 khz. Periods of instability connected to beam conditions? FC stable at high rates. There is an ongoing effort to reduce TPC related EOR reasons. 6. Redundant Ethernet Installation J. Klein gave this presentation, see annexe 5. The installation was carried out during TS3 at the end of September. 12

13 For TRD 27 units installed For TPC 4/5 units - partial installation on the A-side Status Stable operation for TRD and TPC since TS3, though without redundancy. Some uplinks not working on I/ O side need checking. C-side uplinks need to be connected. 7. ALICE upgrade and Technical Board W. Riegler, the Technical Coordinator presented this subject. The ALICE upgrade project has entered a new phase after the endorsement of the upgrade LoI and the ITS CDR. The next goal is to prepare the following Technical Design Reports: For the end of 2013, TDRs for: ITS TPC Electronics upgrade of TOF, TRD, Muons, EMC, PHS and HMP For the end of 2014, TDR for: Online Systems The upgrade must be ready for installation in 5 years from now. There is no time to lose!: A strategy group needs to be established for the needs of forward detectors this by the next Miniweek in November. As from November there will be full-length Technical Boards from 09:00 12:30. In November Miniweek, Technical Coordination will try to organize a mini workshop to discuss common electronics initiatives for various detectors. Annexes 1. A. Tauro P2 issues and LS1 preparations 2. A. Kurepin Report from run coordination 3. G. Scioli High Lumi p-p run and p-a preparations 4. C. Lippmann TPC status operating at nominal gain and high intensity 5. J. Klein Redundant Ethernet installation 6. W. Riegler ALICE upgrade and Technical Board Presentations from the TB/ TF 11 th September can be found at: 13