Precision Drift Chambers for the ATLAS Muon Spectrometer

Susanne MohrdieckMax-Planck-Institut f. Physik, Munich

for the ATLAS Muon Collaboration

Abstracts: 344,350,646

International Europhysics Conference on High-Energy Physics

17.-23.7.2003

Outline: Introduction - ATLAS and the muon spectrometer Precision chamber production Monitoring and measurement of chamber quality/accuracy Performance test of precision chambers under LHC operating conditions

The ATLAS Muon SpectrometerATLAS at LHC: multi-purpose detector to search for Higgs and new physics

Muon Spectrometer:

• toroidal magnetic field: <B> = 0.4 T high pt-resolution independent of the polar angle

• size defined by large lever arm to allow high stand-alone precision

• air-core coils to minimise the multiple scattering

• 3 detector stations- cylindrical in barrel- wheels in end caps

• coverage: || < 2.7

used technologies:• fast trigger chambers: TGC, RPC• high resolution tracking

detectors: MDT, CSC

Performance

goal: high stand-alone µ-momentum resolution of 2-10% !

chamber resolution: 50 µm monitoring of high mechanical precision during production

elaborate optical alignment system to monitor chamber deformations and displacements

see talk by C.Amelung in this talk

at 1TeV: = 10% sagitta = 500 µm

Monitored Drift Tube Chambers (MDT)

End Cap

Barrel• 6 / 8 drift tube layers, arranged in 2 multilayers glued to a spacer frame• length: 1 – 6 m, width: 1 – 2 m• optical system to monitor chamber deformations

• gas: Ar:CO2 (93:7) to prevent aging, 3 bar

• chamber resolution: 50 µm single tube resolution: 100 µm required wire position accuracy: 20 µm

Status of MDT Production

production at 13 sites in 7 countries:• assembly layer by layer using precision table with precise ‚combs‘

• on-line monitoring of temperature and mechanical movements

MDT Production (all sites)

0

200

400

600

800

1000

1200

1400

Jul-00 Jan-01 Jul-01 Jan-02 Jul-02 Jan-03 Jul-03 Jan-04 Jul-04 Jan-05 Jul-05 Jan-06

Time

No

. C

ham

bers

Plan Bare Chambers

Bare Chambers

Chambers with Services

production within schedule:

• 58% of 1194 chambers assembled

• will be finished middle of 2005

Plan for Bare ChambersBare ChambersChambers with Services

MPI Munich

Drift Tube Production

• automated wiring machine

• elaborate quality checks total rejection of only 2.6%

• 73% of in total 370.000 tubes produced

MDT chambers consist of up to 432 drift tubes:

tube wall: 0.4 mm Al

30 mm diameter

wire: 50 µm W-Re endplug

production at NIKHEF

• precise wire positioning in the endplugs:

rms of 7µm

Wire Positions with a X-Ray Method

accuracy of wire position measurement: 3 µm

measurement of the intensity as function of the motor position

average wire positioning accuracy:15 µm

selected chambers tested: 74 of 650 chambers produced at 13 sites scanned so far

X-tomograph at CERN

mechanical precision measuredwith X-ray method

Monitoring of Chamber Quality

monitoring of the chamber parameters by optical sensors during the production (e.g. MPI f. Physik, Munich)

• stable over time

• agreement with X-ray method

X-rayed MPI chambers

20

µm

40

µm

combination of all monitoring results: - chamber parameters- tube positions within a tube layer- wire positions within the tube

Monitoring of Wire Positions

• good agreement between X-ray method and monitoring results y = ymonitoring – yX-ray

- average rms(y) = 19 µm

• comparison to nominal positions: - stable wire positioning accuracy - average rmsy = 18 µm

required accuracy achieved

deviations of monitoring to X-ray method

rms of deviations from nominal positionsin the monitoring (MPI)

MPI

wire positions in all chambers

<rmsy> = 18 µm

Cosmic Ray Test

goals:

• check functionality of all tubes and electronics channels

• measurement of wire positions

e.g. Test Facility at the University of Munich

• deviations from nominal positions compared to X-ray results: rmsy = 25 µm, rmsz = 9 µm

z

y

Cosmic Ray Test (cont)

z displacement for the tube layers

z-pitch for the tube layers

• good agreement with X-ray results

• extraction of layer positions with high precision: 2 µm in z

4 µm in y

• precision for z-pitch: 0.3 µm per layer

University of Munich

10 µm

0.4 µm

Performance under LHC Conditions

degradation due tospace charge fluctuations

required resolution maintained even at high irradiation:

• 104 µm without irradiation • degradation by 10 µm at highest ATLAS rates of 100 s-1cm-2

single tube resolution vs. drift radius

, Ar:CO2(93:7), 3 bar

operation at unprecedentedly high n and background rates:

8 – 100 s-1cm-2

performance test of a large 6-layer chamber:• high energy µ beam (100 GeV)

• -ray irradiation (Cs-137 source with 740 GBq)

• external reference (silicon beam telescope)

Single Tube Resolution

Efficiencies

even at highest expected irradiation no deterioration of track-reconstruction efficiency

track-reconstruction efficiency

extraction of tracking efficiency using the reference track in the Si telescope

total track-reconstruction efficiency:

• ( 99.97 )% without irradiation

• ( 99.77 )% at highest ATLAS rate (for 4m long tubes)

highest ATLAS rate

for 4m long tubes

+0.03- 0.9

+0.23- 0.8

Conclusions

• Precision MDT chamber production within schedule (58% assembled)

• Wire positioning measured with several methods during production

required accuracy of 20 µm achieved

• Performance under LHC conditions tested

at highest background rates chamber resolution of 50 µm maintained

no deterioration of track-reconstruction efficiency

old slides/additional info

Drift Tube Quality

centering of the wire within a drift tube: rms of 7µm

dark current (0.11 %)

rms x/y = 7 µm

wire positionapply quality cuts on gas thightness, dark current, ...

total rejection of 2.6%

gas leak (1.29%)wire tension (0.26%)

NIKHEF

Performance under LHC Conditionsn and background counting rates in s-1 cm-2

operation at unprecedented high background rates:

8 – 100 s-1cm-2

performance test of a large 6-layer chamber at CERN:

• high energy µ beam (100 GeV)

• -ray irradiation (Cs-137 source with 740 GBq)

• external reference (silicon beam telescope)

Single Tube Resolution

degradation due tospace charge fluctuations

resolution vs. drift radius

required resolution maintained even at high irradiation:

• 104 µm without irradiation

• degradation by 10 µm at highest ATLAS rates of 100 s-1cm-2

, Ar:CO2(93:7), 3 bar

Performance under LHC Conditionsn and background counting rates in s-1 cm-2

operation at unprecedented high background rates:

8 – 100 s-1cm-2

performance test of a large 6-layer chamber at -ray irradiation facility at CERN (Cs-137 source with 740 GBq)

(external reference)

Single Tube Resolution

degradation due tospace charge effect

good resolution even at high irradiation

irradiation <resolution>

no irradiation 104 µm

64 Hz/cm2 111 µm

121 Hz/cm2 116 µm

183 Hz/cm2 125 µm

resolution vs. drift radius

for the muon chambers:

Efficienciessingle tube efficiency

irradiation rate / tube [%]

none 0 99.70 ± 0.02

64 Hz/cm2 73 kHz 99.62 ± 0.02

121 Hz/cm2 138 kHz 99.60 ± 0.02

183 Hz/cm2 209 kHz 99.55 ± 0.03

irradiation 3 [%]

no irradiation 93.3 ± 0.2

64 Hz/cm2 89.8 ± 0.2

121 Hz/cm2 86.1 ± 0.2

183 Hz/cm2 80.3 ± 0.3

3 probability of real hit

high efficiencies also at high rates

3 at no irradiation 1 due to e‘s

even at high level of irradiation efficient tracking possible

track-reconstruction efficiency for different numbers of track hits

Status of Chamber Production at Different Sites

MDT/CSC Chamber production: Status 31-May-03

series module-0 series plan series series MDT plan 100%tubes chambers bare chambers bare chambers with gas, FC bare chamb.

Greece - BIS 23,900 2 84 79 0 28. May 04Boston - EI, EM 20,611 1 61 62 61 30. Jun 04Univ. Michigan - EM 29,789 1 71 59 70 30. Jun 04Univ. Washington - EI, EM 26,400 1 68 60 68 30. Jun 04Dubna/Munich - BOS/BOF 33,800 1 63 56 7 13. Aug 04Frascati - BML 22,400 1 69 55 10 08. Nov 04Cosenza/Roma - BIL/BIR 11,100 1 34 34 10 30. Nov 04Dubna - BMS 19,000 1 50 44 0 30. Aug 04Protvino - EO 40,000 1 94 83 14 02. Aug 05Nikhef - BOL 25,608 1 52 53 2 28. Aug 04Cosenza, Pavia - BIL/BIR 11,100 1 24 30 1 30. Nov 04Freiburg - BOG 80 0 0 0 0 01. Nov 04Beijing - BEE, BIS8 211 0 0 0 0 30. Dec 05Sum 263,999 12 670 615 243 Fraction produced 71.1% 57.6% 52.9% 20.9%

total produced total produced total produced160 106 32 13 32 7

panels bare chambers certified chambers

MDT

CSC