ALICE muon trigger (bakelite RPCs): performance and issues Dark rate - PowerPoint PPT Presentation

ALICE muon trigger (bakelite RPCs): performance and issues Dark rate Average distribution 2011 RPC vs Dark rate efficiency distribution 2013 vs time Performance: • Efficiency: stable and uniform (>95%) Average RPC current • Cluster size: stable and in line with R&D values vs average RPC • Dark rate: stable, < 0.05 Hz/cm 2 hit rate • Dark current: globally stable Issues: • A few RPCs show an important increase of dark current (apparently not correlated with the integrated charge) • A few issues with gas tightness (mechanical stress on beaks at in/outlets)

ALICE muon trigger (bakelite RPCs): extrapolation to Run 2, 3 and 4 • Based on the measured correlation between luminosity and counting rate (extrapolation + energy rescaling) • Counting rate in Pb-Pb at 6x10 27 s -1 cm -2 : JINST 7 T12002 30 Hz/cm 2 on average (2012) 55 Hz/cm 2 for the most exposed RPC • Counting rate in pp at 10 31 s -1 cm -2 : 9 Hz/cm 2 on average 15 Hz/cm 2 for the most exposed RPC (does not include the rate from beam-gas , which could be on the same order of magnitude) • Extrapolated Mhits/cm 2 at the end of Run 2: 165 on average, 290 for the most exposed RPC • Extrapolated Mhits/cm 2 at the end of Run 4 : 300 on average, 500 for the most exposed RPC N.B. : these extrapolated rates and fluences do not include any safety factors Beam and ageing tests ( Nucl. Phys. B.PS 158 2006 149 ) in the present running mode: rate capability ~60 Hz/cm 2 , certified lifetime ~500 Mhits/cm 2 -> operation in Run 3 and Run 4 is at the limit of the detector capabilities in the present running mode (maxi avalanche, charge/hit ~ 100 pC) -> upgrade the FEE electronics by adding amplification, so that RPCs can work at lower gain

ALICE : Muon Tracking cathode pad chamber performance during RUN I • The Muon Tracking detector managed to collect high precision data for physics analysis. • The cluster charge distribution over different data taking periods are very similar. • The variation of the peak of cluster charge distribution is due the different voltage setup. • The Muon Tracker achieved position resolution of 250 𝜈𝑛 and 800 𝜈𝑛 in the bending and non-bending planes, respectively. • Most importantly, Muon Tracker managed to measure the 𝐾/𝜔 and Υ resonances at mass resolution of ~70 MeV and ~100 MeV, respectively, which was the design criteria of the detector.

ALICE TOF (glass MRPCs): performance and issues  active are of 141 m 2 , 152928 readout TOF matching efficiency defined as the ratio of the tracks channels.  made of 1593 glass MRPCs (10 gas gaps 250 matched at TOF to those reconstructed using the ALICE μm width) operated in saturated avalanche tracking detectors. It is not the MRPC efficiency because it is mode. also affected by:  gas mixture C 2 H 2 F 4 /SF 6 (93:7). • TOF geometrical acceptance  low noise rate ≈ 0.5 Hz/pad (1 pad = 2.5 × • Uncertainties in the track extrapolation 3.5 cm 2 pick-up element). • Interaction with materials in front of the TOF 1 TOF matching efficiency • Track-TOF matching algorithm inefficiency Eur. Phys. J. Plus Volume 128, 0.9 Issue 4 (2013) 0.8 Agreement between data and MC within 1%. MRPC 0.7 detection efficiency in the MC is set to 98.5% , determined 0.6 by assuming 99.5% of efficiency in the center of the readout MC p-Pb 2013 0.5 pads, as measured from test beam results, and a small drop 0.4 Data p-Pb 2013 close to the pad boundaries 0.3 0.2 1 TOF matching efficiency 0.9 0.1 0.8 0 0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 Ratio 0.7 1.1 p (GeV/c) 1 T 0.6 0.9 0.5 Data p-Pb January 2013 0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 0.4 Data pp May 2012 p (GeV/c) T 0.3 Data pp March 2011 The TOF matching efficiency was stable throughout the 0.2 Eur. Phys. J. Plus Volume 128, years. The bump at low p T is due to different material Issue 4 (2013) 0.1 budget in front of the TOF before and after 2012. 0 0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 p (GeV/c) T

ALICE TOF (glass MRPCs): performance and issues Estimated rate in p-Pb at 10 29 Current drawn in p-Pb at cm -2 s -1 is ~ 14 Hz/cm 2 (good 10 29 cm -2 s -1 was ~ 130μA agreement with expectations (less than 100nA per MRPC from FLUKA simulations). or 1 uA/m 2 ). Eur. Phys. J. Plus Volume 128, Issue 4 (2013) The MRPCs current increased linearly with the LHC Charged particle rate at TOF has been estimated offline luminosity with no sign of the deviations related to the considering the TOF raw hit multiplicity per event and occurrence of abnormal noise current. the ALICE interaction rate. From this rate and the total current of the MRPCs we compute an average induced charge of 6 pC per track. ISSUES:  25 out of 1593 ( 1.6% ) MRPCs OFF at the end of Run 1 due to HV failures. Problems not in the MRPCs (no high currents nor discharges between anode and cathode), most probably in the HV connectors or distributors. Problems are inside the gas tight volume or in zone difficult to access. Not clear whether we can improve that situation during LS1.  Major troubles in Run1 due to LV power supplies working in B-field (DCDC converters). New design validated (no failures with a sample of new DCDCs operated in ALICE during all 2012), full replacement under way.  Few % of readout channels OFF due to broken or noisy readout electronics boards.

ALICE TOF (glass MRPCs): extrapolated background Pb-Pb at 6 10 27 cm -2 s -1 (5.5 TeV/NN) from FLUKA : 95 Hz/cm 2 max. lumi = 6 10 27 cm -2 s -1 avg. lumi = 2.4 10 27 cm -2 s -1  Charged particle rate in Pb-Pb at 2.4 10 27 cm -2 s -1 : 38 Hz/cm 2  Charged particle rate in Pb-Pb at 6 10 27 cm - 2 s -1 : 94 Hz/cm 2 MRPCs tested at CERN GIF showed no loss in  Integrated charge at the end of Run1: 0.2 mC/cm 2 performance up to 1 kHz/cm 2  Extrapolated charge at the end of Phase I: 1.9 mC/cm 2 ( Nucl. Instr. Meth. A490(2002) 58 ).  Extrapolated charge at the end of Phase II: 2.8 mC/cm 2 Calculations doesn’t account for beam-gas (results should not change significantly) With ageing tests at CERN GIF we didn’t observe any sign of degradation nor increase of dark current after collecting a total amount of 14 mC/cm 2 . A search for HF in the outgoing gas, using gas chromatography, gave negative results (below 0.02 ppm). A MRPC that collected a charge of 10 mC/cm 2 was carefully measured before and after irradiation; we did not observe any efficiency and time resolution degradation ( Nucl. Instr. Meth. A 533 (2004) 93 – 97 ). NO UPGRADE FORESEEN

Scenarios used in the extrapolations (1/2) RUN2: Year System Luminosity 10 29 -10 30 cm -2 s -1 2015 pp – min bias (24 weeks) 10 27 cm -2 s -1 - leveled Pb-Pb – 4 weeks 2016 pp – rare triggers (24 weeks) 5-10 10 30 cm -2 s -1 10 27 cm -2 s -1 - leveled Pb-Pb – 4 weeks 5-10 10 30 cm -2 s -1 2017 pp – rare triggers (24 weeks) 0.5-1 10 28 cm -2 s -1 - leveled p-Pb – min bias (2 weeks) 1 10 29 cm -2 s -1 - leveled p-Pb – rare triggers (2 weeks)  Table from RLIUP workshop (29-31 October 2013). In the above calculations we considered scenarios with largest luminosity values. RUN3: 2020 pp (1y for detector 6 10 30 cm -2 s -1 recommissioning) Pb-Pb 2.85 nb -1 2.4 10 27 cm -2 s -1 - leveled 2021 Pb-Pb 2.85 nb -1 at low magnetic 2.4 10 27 cm -2 s -1 - leveled 2022 field  Values from ALICE Upgrade LoI. For pp we considered the peak luminosity.

Scenarios used in the extrapolations (2/2) RUN4: Year System Luminosity 2025 pp (1y for detector 6 10 30 cm -2 s -1 recommissioning) 2026 Pb-Pb 2.85 nb -1 2.4 10 27 cm -2 s -1 - leveled Pb-Pb 1.42 nb -1 2.4 10 27 cm -2 s -1 - leveled 2027 p-Pb 50nb -1 10 29 cm -2 s -1 - leveled Pb-Pb 2.85 nb -1 2.4 10 27 cm -2 s -1 - leveled 2028  Values from ALICE Upgrade LoI. For pp we considered the peak luminosity.