Status & Readiness of the ATLAS Muon Spectrometer

Status & ReadinessStatus & Readiness of the of the

ATLAS Muon SpectrometerATLAS Muon Spectrometer

J. Chapman - University of Michigan

on behalf of the ATLAS Muon Groups

Particular Thanks to C. Ferretti, D. Levin,

E. Diehl & A. Belloni (Harvard)

Workshop of the AmericasWorkshop of the Americas

NYU August 4, 2009NYU August 4, 2009

Workshop of the Americas (NYU) – J. Chapman

Overview StatusOverview Status

2

• Hardware almost completed– Status at closure:– MDT Endcap fibers replaced– RPC nearing 95.5% coverage– TGC ready soon, after 7 months

• ATLAS DAQ functioning well– CSC working to reach design L1 rate

• Most data from 2008 runs• Muon Sub-detector will be

ready for collisions!4-August-2009

Workshop of the Americas (NYU) – J. Chapman 3

OutlineOutline

• Very Quick Detector Description

• Sub-detectors Status

• Detector Control System Status

• Challenges to Precision Calibration

• Alignment System – next talk

• Commissioning Results

• Conclusions4-August-2009

Workshop of the Americas (NYU) – J. Chapman 4

ATLAS Muon SpectrometerATLAS Muon Spectrometer• Three stations in an air-core toroidal magnetic field

(superconducting) (barrel: |η|<1.4 , endcap: 1.6<|η|<2.7)• Four different technologies:

– Monitored Drift Tubes (MDT): precision chambers in the bending direction– Cathode Strip Chambers (CSC): precision chambers at |η|>2.0– Resistive Plate Chambers (RPC): trigger |η|<1.05 + 2nd coordinate– Thin Gap Chambers (TGC): trigger 1.05<|η|<2.4 + 2nd coordinate

• Performance goal: stand-alone Δp/p~10% at 1 TeV sagitta ~ 500 μm along measured with a resolution ~50μm

#chambers #channels Resolution (RMS)

MDT 1150 354k 35 μm (z&R) -

CSC 32 30.7k 40 μm (R) 3-7 mm (φ)

RPC 606 373k 10 mm (z) 5 mm (φ)

TGC 3588 318k 2-6 mm (R) 10 mm (φ)

4-August-2009


Spectrometer LayoutSpectrometer Layout

4-August-2009 5

Beam View

Side View

Muons cross 3 layers of precisionchambers for sagitta measurementTrigger chambers are placed onboth sides of middle precision layer (+ a few elsewhere)


• System features low failures– Readout channels: ~0.2%– T-sensors: ~0.3%– B-sensors: ~0.5%– Alignment: ~1-2%

• Final actions taken– Fiber replacement C & A side– Replaced a few faulty cards &

sensors, sealed gas leaks– Switched barrel mezzanines to

50MHz & exchanged a few cards that did not operate successfully at higher speed

• Single-hit efficiency above 99%• Hit resolution near design value

Monitored Drift TubesMonitored Drift Tubes

4-August-2009 6

Chambers in DAQ (2009)


MDT OccupancyMDT Occupancy

4-August-2009 7

MDT Occupancy – chamber Φ vs ηHot spots due to access shafts circled

1090/1150 Chambers installed – 99.6% operational

TGC vs MDT correlationLines ↔ noisy channels


• Additional MDTs– EEL Sector 5 installed– Mounted on Toroid

• Other sectors soon– EELA11 next– EELA14 follows

• Side C follows A– Schedule is

uncertain

EE Chamber InstallationEE Chamber Installation

4-August-2009 8

Workshop of the Americas (NYU) – J. Chapman4-August-2009 9

RPC StatusRPC Status• 95.5% operative (out of 396 towers)

• < 4% broken HV connectors or electronic components

• < 1% leaky gas channels

• Temperature problem forces top sectors to run at 9.2kV (9.6kV)


• Cosmic data provides good evaluation of RPC– Hit efficiency in the high 90% region – expect the

tails to be reduced with HV tuning– Resolution is as expected

• Timing calibration for trigger is underway

RPC PerformanceRPC Performance

4-August-2009 10


RPC Performance with MDT RPC Performance with MDT trackstracks

4-August-2009 11

Efficiency for BM chambers with HV=9.6kV, Vth=-1V

BM

Residual distribution normalized to strip pitch

- Events triggered by RPCs with ¾ majority- Only 1 MDT track reconstructed by MuonBoy- Look at 4th layer when trigger justified offline by 3 layers

113860

BM113860

From: G.Aielli


TGC StatusTGC Status• All chambers installed with final gas CO2: n-C5H12 (55:45)

• Now: 3 chambers (less than 0.8‰) are problematic

• TGC trigger worked very well during DAQ periods

Fall 2008 data

TGC trigger timing


• Low rate of faulty channels– ~0.02% in Middle Layer– ~0.5% in Inner Layer– No holes in coverage

• L1 rate limited to 45kHz– Redundant information

removed. Ready for tests

• Last runs (HV+gas) in 2008– MDT/TGC work halted runs– Oil contamination of gas

damaged vessel. System will be back mid August 2009

TGC PerformanceTGC Performance

4-August-2009 13


• 2 of 128 panels unusable– covered by redundancy

• New ROD firmware progress– Current status: max L1 rate < 1kHz;– ROD crashes after ~1k events fixed– Test stand & two SLAC engineers at

CERN for redesign effort

• Commissioning the CSC with cosmics is difficult– Low probability to hit CSC– Only 50k events in 2008 with 199, 4-

hit segments in CSC.

CSC StatusCSC Status

4-August-2009 14


• Knowing the drift time R-T function & offset t0.– Depends on gas temperature, composition, & pressure– Depends on pulse amplitude (time walk) & wire sag

– Depends on electronics delays & trigger timing (t0)

• Knowing the chamber alignment & B-field• Sensitivity figures:

– Drift velocity at wall is ~20μm/ns (50μm in 2.5ns)– t of 7oC corresponds to ~ 17ns ( many )– Wire sag for largest chambers ~ 500m– Plots for other variables visible in gas monitor

Securing & Maintaining Securing & Maintaining PrecisionPrecision

4-August-2009 15


MDT Detector Control SystemMDT Detector Control System• The DCS provides initialization of the chambers and reads out

– voltages/temperatures of ~18k F.E. electronic cards and power supply– over 13k temperature sensors– ~2k Hall probes– gas parameters– alignment system– ...

• Note: 7oCvariation frombottom to top!

T>25°C

T<18°C


MDT Gas Monitoring & PromptMDT Gas Monitoring & PromptCalibrationsCalibrations

4-August-2009 16

Recycler

gas supply line• Track gas quality via maximum drift time

• Compare behavior of MDT gas for supply and exhaust lines

• Precision: below 1ns in the maximum drift time measurement, once/hour

• Universal Time-to-Radius (RT) relations published every two hours

• Gas volume exchange– Muon Spectrometer

~2 weeks refresh – Gas Monitor ~2 hours

gas exhaust

(D. Levin, N. Amram et al)


MDT gas Drift-time (TMDT gas Drift-time (Tmaxmax ) & Cavern ) & Cavern HumidityHumidity

4-August-2009 18

ns

Oct 2007 Dec 2008

t = 720-685ns = 35ns

• Monitoring TDC spectra continuously since August 2007• Results displayed at mdtgasmon.grid.umich.edu• Transients due to gas system interventions or occasional component failures• Overall variation in maximum drift time caused by gas mixture change from

– External humidity– Intentional water vapor injection

http://mdtgasmon.grid.umich.edu/gasmon/


MDT Calibration with Cosmic-raysMDT Calibration with Cosmic-rays• Difficult due to asynchronous nature of cosmic rays

with LHC clock 25ns and variable TOF between trigger and precision chambers. Recovered by t0-tuning algorithm.

• Dedicated L2 stream 3 centers for all chambers in 24h

• Collision data critical to obtain final precision

Residuals vs. Radiust0 fit


Segment Reconstruction PerformanceSegment Reconstruction Performance

Fall 2008<ε>=98.4%

Performance from clean sample:• No shower (#segments/event<20)• Track passing at least 2 stations• Extrapolation pass the 3rd station• Segment on each stationInner

layer

Outerlayers

For cosmic rayso enlarged single-hit error (1 mm)o relaxed matching angleo minimum 3 hits per segment

Efficiency(ε)= #Seg(found)/#Seg(expect)


Track ReconstructionTrack Reconstruction

MDT hits distribution peaked at 12, 14 and 20 (expected)Tails: overlap small-large sectors

Track residual ~ 250 μm worse than segment residual (expected): - misalignment- multiple scattering

Number of hits


Inner Detector vs. SpectrometerInner Detector vs. Spectrometer

ΔP[GeV/c]

Cosmic ray passing in the Inner Detector split in two tracks at the perigee.3 GeV loss in the calorimeter.MS tracks corrected for theEloss compared with ID tracks

Δp(top-bottom)2 x 3 Gev lossin calorimeters


ConclusionsConclusions• Hardware: status very good (nearing completion)• Trigger:

– Coverage much improved from 2008– Timing between detector elements still being tuned

• Calibration:– Calibration centers returning constants in 36 hours– Fine tuning of constants awaiting collision data

• Alignment: Chamber position & orientation known• Track segment finding, reconstruction efficiency, &

resolution is improving & will continue to improveStill a lot of work to do, but the ATLAS Muon

Spectrometer is ready for beam

Backup SlidesBackup Slides

Alignment Issues


Layers, Locations, & LabelsLayers, Locations, & Labels

4-August-2009 25

EOEM

EI


Fake SegmentsFake Segments Form pattern recognition: 1 track should to give 1 segment/station

From noise hits: study #segments far from the only track in the event

Fall 2008avg=1.1

Fall 2008avg=2.3·10-4


ATLAS Muon DetectorATLAS Muon Detector

Barrel |η|<1.05: I=inner, M=middle, O=outer layersof RPC + MDT in S=small and L=large sectors

Endcap 1.05<|η|<2.7three wheels (Small, Big, Outer) of TGC + MDT/CSC


MDT/CSC StatusMDT/CSC Status• 1090/1150 MDT + 32/32 CSC chambers installed • Shutdown: recovered ~7k MDT tubes, replaced MDT BW

optical fibers, doubled speed for all MDT readout electronics • Now: > 99.5 % MDT channels operational and 99.9% of the

chambers are read by the ATLAS DAQ + 98.5 % CSC layers• Work continuing on CSC readout Driver (ROD) firmware

Inner, Middle and OuterMDT occupancy

(Fall 08): sector vs. ηID


Precision Chambers AlignmentPrecision Chambers Alignment• Grid of ~12k optical sensors monitoring/reconstructing

chamber position, rotation angles and deformations• Track-based alignment used for global positions (Endcap

Wheels-Barrel and Spectrometer-ID)• After shutdown over 99% of the devices working and the

degradation due to a few missing sensors is negligible

Barrel Endcap


Barrel Alignment: Large vs. Small SectorsBarrel Alignment: Large vs. Small Sectors


Alignment in the BarrelAlignment in the Barrel• 105 μ±(20 GeV) enough to align at

30 μm (Small sectors: 5×statistics)

• Initial geometry + alignment traces

displacement in relative mode

• Track + alignment parameters inside one global fit (correlations included)

• Tracks (magnetic field off runs)

– Close to the IP (precision plane)

– Traversing 3 stations

– Straight line fit inner-outer MDT

– Residuals in the middle chamber

~ sagitta = 22±7 μm


Alignment in the EndcapAlignment in the Endcap

• Corrected sagitta = 2±27 μm– 3 segments tracks (EI-EM-EO) in the same sector– Angle segments-straight line EI-EO segments < 5/50 mrad (sagitta only)– At least 1 trigger phi hit (good 2nd coordinate measurement)


• Designed to trigger on and measure muons with Pt ≳ 3 GeV with resolution 3% < 250 GeV to 10% @ 1 TeV.

• Magnetic field from air-core torroids: barrel + 2 endcap• Trigger detectors (trigger + 2nd coordinate measurement)

– 0<η<1.0 (Barrel) Resistive Plate Chambers (RPC) 373k chan– 1.0<η<2.4 (Endcap) Thin Gap Chambers (TGC) 318k chan

• Precision detectors– 0<η<2.0 Monitored Drift Chambers (MDT) 354k chan– Monitored ⇨Positions monitored by an alignment system– 2.0<η<2.7 Cathode Strip Chambers (CSC) 30.7k chan

• Alignment – determine chamber positions to ~50 μm– Separate optical alignment systems for barrel & endcap

complemented by alignment with tracks.

Spectrometer OverviewSpectrometer Overview

4-August-2009 33

Documents

Status & Readiness of the ATLAS Muon Spectrometer