muon trigger bakelite RPCs performance and issues Performance Efficiency stable and uniform gt95 Cluster size stable and in line with RampD values Dark rate stable lt 005 Hzcm ID: 278717
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Slide1
ALICE muon trigger (bakelite RPCs): performance and issues
Performance: Efficiency: stable and uniform (>95%) Cluster size: stable and in line with R&D values Dark rate: stable, < 0.05 Hz/cm2 Dark current: globally stableIssues: 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)
Average
RPC current vs average RPC hit rate
Dark rate distribution
2011vsDark rate distribution 2013
Average
RPC
efficiency
vs
timeSlide2
ALICE
muon trigger (bakelite RPCs): extrapolation to Run 2, 3 and 4JINST 7 T12002 (2012) Extrapolated Mhits/cm2 at the end of Run 2: 165 on average, 290 for the most exposed RPC Extrapolated Mhits/cm2 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/cm2 , certified lifetime ~500 Mhits/cm2
-> 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 Based on the measured correlation between luminosity and counting rate
(extrapolation + energy rescaling)
Counting rate in Pb-Pb at 6x1027s-1cm-2 : 30 Hz/cm2 on average 55 Hz/cm2 for the most exposed RPC Counting rate in pp at 10
31 s-1 cm-2: 9 Hz/cm2
on average 15 Hz/cm2 for the most exposed RPC (does not include the rate from beam-gas
, which could be on the same order of magnitude)Slide3
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
and
in the bending and non-bending planes, respectively.Most importantly, Muon Tracker managed to measure the
and
resonances at mass resolution of ~70 MeV and ~100 MeV, respectively, which was the design criteria of the detector. Slide4
TOF matching efficiency
defined as the ratio of the tracks matched at TOF to those reconstructed using the ALICE tracking detectors. It is not the MRPC efficiency because it is also affected by:TOF geometrical acceptanceUncertainties in the track extrapolation
Interaction with materials in front of the TOF
Track-TOF matching algorithm inefficiencyAgreement between data and MC within 1%. MRPC detection efficiency in the MC is set to 98.5%
, determined by assuming 99.5% of efficiency in the center of the readout pads, as measured from test beam
results, and a small drop close to the pad boundariesThe TOF
matching efficiency was stable throughout the years. The bump at low pT is due to different material budget in front of the TOF before and after 2012.
ALICE TOF (glass MRPCs): performance and issues
Eur
. Phys. J. Plus Volume 128, Issue 4 (2013)
active are of 141 m
2
,
152928 readout channels.
made of 1593 glass MRPCs (10 gas gaps 250
μm
width) operated in saturated avalanche mode.
gas
mixture
C
2
H
2
F
4
/SF
6 (93:7).low noise rate ≈ 0.5 Hz/pad (1 pad = 2.5 × 3.5 cm2 pick-up element).
Eur
. Phys. J. Plus Volume 128, Issue 4 (2013)Slide5
ALICE TOF (glass MRPCs): performance and issues
The MRPCs current increased linearly with the LHC luminosity with no sign of the deviations related to the occurrence of abnormal noise current. Charged particle rate at TOF has been estimated offline considering the TOF raw hit multiplicity per event and 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.
Eur
. Phys. J. Plus Volume 128, Issue 4 (2013)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.Current drawn in p-Pb at 1029 cm-2s
-1 was ~ 130μA (less than 100nA per MRPC or 1 uA/m
2).
Estimated rate in p-Pb at 1029 cm
-2
s
-1
is
~ 14 Hz/cm
2
(good agreement with
expectations from
FLUKA simulations).Slide6
avg.
lumi = 2.4 1027 cm-2s-1max. lumi = 6 1027 cm-2s-1Integrated charge at the end of Run1: 0.2 mC/cm2
Extrapolated charge at the end of Phase I: 1.9 mC/cm
2Extrapolated charge at the end of Phase II: 2.8 mC/cm2Calculations 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/cm2. 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/cm2 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
ALICE TOF (glass MRPCs): extrapolated background
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 1027cm-2s-1 : 94 Hz/cm2MRPCs tested at CERN GIF showed no loss in performance up to 1 kHz/cm2 (Nucl. Instr.
Meth
. A490(2002) 58
).
Pb
-Pb
at
6
10
27
cm
-
2
s
-1
(5.5 TeV/NN) from
FLUKA
:
95
Hz/cm
2Slide7
Scenarios used in the extrapolations (1/2)
YearSystemLuminosity2015pp – min bias (24 weeks)1029-1030 cm-2s-1Pb-Pb – 4 weeks1027 cm-2
s-1 - leveled2016
pp – rare triggers (24 weeks)5-10 1030 cm
-2s-1
Pb-Pb – 4 weeks1027 cm-2s-1 - leveled2017
pp – rare triggers (24 weeks)5-10 10
30 cm-2s-1
p-Pb – min bias (2 weeks)
0.5-1 10
28
cm
-2
s
-1
- leveled
p-
Pb
– rare triggers (2 weeks)
1 10
29
cm
-2
s
-1
- leveled
RUN2:RUN3:2020pp (1y for detector recommissioning)
6 10
30
cm
-2
s
-1
2021
Pb-Pb
2.85 nb
-1
2.4 10
27
cm
-2
s
-1
- leveled
2022
Pb-Pb
2.85 nb
-1
at low magnetic field
2.4 10
27 cm-2s-1 - leveled
Table from RLIUP workshop (29-31 October 2013). In the above calculations we considered scenarios with largest luminosity values.
V
alues from ALICE Upgrade
LoI
. For
pp
we considered the peak luminosity.Slide8
Scenarios used in the extrapolations (2/2)
YearSystemLuminosity2025pp (1y for detector recommissioning)6 1030 cm-2s-12026Pb-Pb 2.85 nb-1
2.4 1027 cm-2
s-1 - leveled2027
Pb-Pb 1.42 nb-1
2.4 1027 cm-2s-1 - leveledp-Pb
50nb-110
29 cm-2s-1 - leveled
2028
Pb-Pb
2.85 nb
-1
2.4 10
27
cm
-2
s
-1
- leveled
RUN4:
V
alues from ALICE Upgrade
LoI
. For
pp
we considered the peak luminosity.