System Test of the ATLAS Muon Spectrometer in the H8 Beam at the CERN SPS

ATLAS Muon test beam, E. Etzion, NSS 2004

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System Test of the ATLAS Muon Spectrometer in the H8 Beam at

the CERN SPSErez Etzion (Tel Aviv University), Stefano Rosati (CERN)

On behalf of the ATLAS H8 Muon Test Beam Community

IEEE, 2004 Nuclear Science SymposiumRome, Italy, October 17 2004


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MUON Spectrometer• To trigger on MUON’s, one

needs:– Fast detectors to provide moderate

Pt measurement and Bunch ID.– Azimuthal coordinate measurement

for both, MUON tracking and correct the main tracking detectors.

• To track MUON’s with a precision similar or better than the ID, one needs:– Precision detectors, with

deformations that can be followed

– Precise magnetic field mapping

– Alignment system over large distances, (relative position of chambers 30-40 microns.)


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Monitored Drift Tubes

The MDT chambers are made of two multilayers of pressurized aluminium drift tubes separated by

50 to 320mm high spacer and support structure .

A multilayer consist of three (or four) layers of dense-packed drift tubes.

Each tube determines the vertical distance between a charged particle track and the wire from the arrival time of the first ionization electron.

Tubes: -outer diameter :30mm, wall thickness: 0.4mm; Wire:50m(gold-plated)-370.000 channelsGas: -Ar:N2:CH4 -mixture (91:4:5) - pressure:3 bar(absolute)HV:3.25 kV


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Cathode Strip ChambersMultiwire proportional chambers determine muon position by interpolating the charge on 3 to 5 adjacent strips

Precision (x-) strip pitch ~ 5mm

Measure Q1, Q2, Q3… with 150:1 SNR to get x ~ 60 m.

Second set of y-strips measure transverse coordinate to ~ 1 cm.

Position accuracy unaffected by gas gain or drift time variations.

Accurate intercalibration of adjacent channels essential.

S = d = 2.54 mm

W = 5.6 mm

32 four-layer chambers

2.0 < || < 2.7

|Z| ~ 7m, 1 < r < 2 m

4 gas gaps per chamber

31,000 channels

Gas Ar:CO2:CF4 (30:50:20)

High voltage :3.2 kV

32 four-layer chambers

2.0 < || < 2.7

|Z| ~ 7m, 1 < r < 2 m

4 gas gaps per chamber

31,000 channels

Gas Ar:CO2:CF4 (30:50:20)

High voltage :3.2 kV


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Trigger Chambers

• The first level muon trigger is derived from three trigger stations formed of Resistive Plate Chambers (very fast detectors with moderate rate capabilities) in the barrel and Thin Gap Chambers (moderately fast detectors with high rate capabilities) in the end-caps.

• Each station is made of 2(or 3) planes of strips (or wires) with x or y readout .• The trigger is based on a coincidence between a strip (or wire) hit in the 1st

station and a range of strips (or wires) in the 2nd or 3nd station. Typical momentum

resolution is 20%. • Low pt trigger: p>6GeV.• High pt trigger: p>20GeV.


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Resistive Plate Chambers• Resistive Plate Chambers are gaseous,

self-quenching parallel-plate detectors.• They are built from a pair of electrically

transparent bakelite plates separated by small spacers.

Signal are induced capacitively on external readout strips.

- 420.000 channels in 596 double gap chambers.Gas: C2H2F4:isoC4H10 (97:3).HV : 9kV.Performance:-efficiency:>99%.-space-time resolution of 1cm1ns.-rate capability:~1kHz/cm².

- 420.000 channels in 596 double gap chambers.Gas: C2H2F4:isoC4H10 (97:3).HV : 9kV.Performance:-efficiency:>99%.-space-time resolution of 1cm1ns.-rate capability:~1kHz/cm².


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Thin Gap Chambers

wires

strips

supports

-e+ion


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Muon Test Beam setup

BIL on rotating support CSC

Magnet

BOS

MBPL

TGCs

Barrel

Endcap


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Barrel Stand

• 6 barrel MDT chambers (precision tracking) Fully instrumented with FE electronics, readout with 1 MROD Fully equipped with alignment system

• 6 RPC doublets (4 BML and 2 BOL) (LVL1 trigger + tracking) 1 Trigger PAD Being upgraded now to 2 PADS ( LowPt & HighPt)

• The setup is reproducing at full scale one ATLAS barrel sector with 6 MDT+RPC stations

• 2 additional barrel MDT chambers 1 BIL on rotating support for calibration studies 1 BOS station (MDT+RPC) upstream of muon wall for noise

studies and CTB


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BML

BOL

BIL - Rotating


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Endcap Stand

• 11 MDT chambers (2 EI, 2EM, 2 EO) Fully instrumented with FE electronics, readout with 1 MROD Equipped with the complete alignment system (calibrated

sensors for absolute alignment) Reproducing at full scale a muon spectrometer endcap sector

• 3 TGC chambers (2 doublets, 1 triplet) Fully instrumented with on-chamber electronics

• CSC: 1 chamber being installed during last week, should be integrated soon in the combined data taking


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TGC

DoubletsTGC

Triplet


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Data collected until now

• A large sample of data has been collected since June• Main tests performed on detectors:

MDT LV tests in the ATLAS configuration (2 chambers/LV channel) Barrel alignment: large chambers rotations up to 8 mrad Endcap alignment: checks of sensors absolute calibration DCS – sensors, controls Noise and efficiency studies on a large scale (~1% of ATLAS) MDT-RPC cross talk studies MDT threshold scans RPC threshold and HV scans LVL1 trigger validation with TGC during the 25 ns run in June Muon system commissioning and integration

• Triggering during the muon standalone period with 10x10 or 60x100 cm2 scintillators. Self-triggering with TGC or RPC during 25ns period

• Muon detectors are integrated in the Combined Test Beam data taking since mid of August


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Online monitoring

Channel vs Layer: Fast detection of Inefficiency and Noise

Channel vs Layer: Fast detection of Inefficiency and Noise

• Monitoring framework (GNAM) co-developedwith the ATLAS Tile Calorimeter Data sampling at anylevel, Allow user libraries (decoding and histograms filling) Histograms published in the interactive presenter

• Monitoring in ATHENA

Early studies algs and collected Monitor of Event Filter performance

Online presenter (for both GNAM and EF-ATHENA)


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Conditions DB

CondDB

DCS Temperature LV, B field Gas, CSM params

Global Alignment

AlignmentEnd cap,

barrel

Run Parametersfrom DAQ IS

ATHENA

AMI

Plot, Monitor

PVSS interface to MySQL

runs online and offlineJTAG

•Use MySQL with dedicated interface software (MDT) or direct SQL (TGC) •Nearly a complete loop of applications using the conditions data has been implemented • All quantities needed are stored and read• MDT - High rate access for raw alignment image results (~2 sec)•TGC – Tested configuration via online and via DCS. Root, direct web access.•Access from ATHENA analysis enviroenment under development.


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Offline Software• The ATHENA framework is used as offline monitoring, reconstruction and analysis tool

Exploit the test beam data as test for the ATLAS software• ByteStream converters: access to the raw data for all muon technologies (MDT, RPC, TGC,

CSC, MUCTPI): same scheme as for ATLAS Preparing data using ATLAS Muon Event Data Model for: LVL2 (MuFast) , EF (TrigMoore) , offline (MOORE, Muonboy) algorithms

• Detector Description: same as for ATLAS (MuonGeoModel) Initialization from AMDB database primary numbers in NOVA DB, special AMDB version

implemented for the CTB Using same DD for simulation and reconstruction (as in DC2)

• Offline algs (MOORE, Muonboy) as for DC and physics data• Ntuples are produced with ATHENA for offline monitoring

Useful tool for offline monitoring of detector performance Check events correlation among subdetectors Included in the Combined Ntuples Correlation Muon track InDet track


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RPC preliminary results• RPC efficiency can be evaluated comparing MDT segments extrapolation with the position of RPC clusters•Tested cluster sizes and efficiecy for different HV and thresholds•Tested correlation between MDT and RPC

Efficiency vsHV and threshold

Correlation MDT-RPC


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TGC preliminary results• TGC taking data during run with 25ns-bunched beam in June• Validation of the design of the Endcap muon LVL1 trigger• LVL1 trigger signal provided to the MUCTPI

– Sector logic output and MUCTPI match perfectly• DCS – operation and control • Integration with the TGC conditions database• Results on LVL1 trigger performance:

– Low-Pt efficiency 99.4%– High-Pt efficiency 98.1%

Correlation with MDT tracks


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Beam momentum measurement

Momentum

GeV

Mean=108 GeVSigma=4 GeV

Magnet OFF

Magnet ON

• Exploit the bending in MBPL magnet upstream of barrel stand• Reconstruction with MOORE• Compare track angles in BILupstream of MBPL and full barrel

•P=0.3BL/•BL=3.54 Tm


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Beam momentum measurement

• Sigma – not tracking res. depends on collimators settings

• Energy loss due to material upstream of the muon area: calorimeters+3.2 m of iron (muon wall)

Preliminary – MDT threshold 40 mV

Sagitta

Outer

Middle

Sagitta definition at the TB:

• Create r-z (MDT+RPC) and phi segments (only RPC),

perform pattern recognition

• Segments fit on each station

• Combination of inner and outer,compare with middle station

• Misalignment affects mean value and width

• Multiple scattering affects width

Nominal P(GeV)

Measured P (GeV)

Sigma

(GeV)

Sagitta

resolution

(m)

100 88.8 4.34 102

120 108.2 4.06 94

150 135.0 6.84 78

180 166.3 8.83 73

220 206.1 12.11 66

250 230.0 15.11 62


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Comparisons with G4 simulation• Real data/G4 sim reconstruction comparison provides important feedback to the G4 validation effort •First tests: generate muons in the CTB setup (only muon detectors activated for now) at beam energies measured in data• Reconstruction with MOORE• Compare fit residuals and sagitta resolution

Data=61m

G4 =57 m

MDT fit residuals

DataG4

Athena 8.8.0

Sagitta width


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Results on alignment corrections• Tests of the relative alignment system: perform chambers controlled movements and correct using the information from the optical alignment system – many tests successfully performed during 2003 test beam• Results shown here are from barrel controlled movements performed during 2004 data taking (rotations about X axis – beam axis)• Reconstruction with Muonboy in ATHENA

Rotations at the limit of the dynamical range of the alignment system(~8 mrad)

Absolute alignment is being validated (sensors calibrations)Similar studies ongoing for the endcap system


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Conclusions• The muon test beam has profited of many years of tests and

experience of the muon group in H8• Many aspects of detectors integration and combined data taking

have been tested• Data taking is going on since June, Shown here:

Detector and trigger performance Detector operation and control Use of the offline software framework (ATHENA) Reconstruction algs. studies Comparisons of G4 simulation with real data Alignment

• Further studies: Another run with 25 ns bunched beam (2 weeks ago) RPC and TGC LVL1 trigger

Complete the integration of the muon trigger slice (LVL1-LVL2-Event Filter)

Alignment of the muon system Combined data taking Combined alignment, reconstruction and physics studies

Thank you

Documents

System Test of the ATLAS Muon Spectrometer in the H8 Beam at the CERN SPS