First Reconstruction ResultsFirst Reconstruction Resultson the Alignment of Muon on the Alignment of Muon Endcap Chambers in the Endcap Chambers in the CMS Experiment at CERNCMS Experiment at CERN

S. Guragain, G. Baksay, M. Hohlmann

Florida Tech

74th Annual meeting of SESAPS, Nashville, TN, Nov 8-10, 2007

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CMS detector of LHC @ CERNCMS detector of LHC @ CERN

CMS solenoid -13 m long

Magnetic field - 4 TeslaTotal weight - 12500 tOverall diameter -15 m

Overall length - 21.6 m

Muon Endcaps

ME+1ME+2ME+3ME+4

ME -

Z+

Compact Muon Solenoid

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A part of CMSA part of CMS

2 Crosshair Lasers (adjustable)

Ref. DCOPS

Chamber DCOPS’s

Transfer Line

DCOPS

Z-tube

Z-sensors

Transfer Plate

Clinometer

MountingTower

ME+2 SLM

BackCham

ber

R-sensor

Laser beam

Laser on !ZCMS

RphiCMS

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Full Reconstruction ModelFull Reconstruction Model

R-sensors

Z-sensors

Note: only smallsample of analog sensors shown

ClinometersTransfer plate

DCOPS’s

Straight Line Monitors (SLMs)and Transfer lines

Lasers

SLM currently under study (ME+2 SLM 2-5)

Lasers

Chamber resolution 75 micron for ME1/2

and 150micron for other.

The system monitors the positions of

CSCs relative to each other and to the

MABs

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Basic strategyBasic strategy

• Fit DCOPS data at B=0T and reconstruct DCOPS and CSC positions using COCOA (CMS Object-oriented Code for Optical Alignment)

• Check B=0T reco results for one SLM against photogrammetry (PG) in full detail and with great care until we can trust the reconstruction

• Quantify precisions and accuracies

• Reconstruct DCOPS & CSC positions at B=4T

• Apply lessons learned to reco of other SLMs

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Simultaneous fit in zSimultaneous fit in zCMS CMS for two for two

lasers in ME+2 SLM2-5 at B=0Tlasers in ME+2 SLM2-5 at B=0T

DCOPSCCDs

B=0T

Laser hits(shifted to the sides of CCDs for display)

CCD2 CCD4CCD2 CCD4

fitted position

First CCD pixels

Simultaneous fitting of 2 laserswith hits that overlap on 4 central

DCOPS’s is now working !

Ref. CCDRef. CCD

bad hitsnot usedin fit

Note: In MTCC 2006 the lasers were tilted towards the CSCs on purpose to compensate for disk bending at B=4T !

laser line fitlaser line fit

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Fit ResidualsFit Residuals

Precision in zCMS (“z-resolution”) ≈ 60 m

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Dowel pins

Reconstructed tops of CSC Alignment pins

Reconstructed tops of DCOPS boxes

First CCD pixels

Reconstructed positions of outer CSC PCB skins

B=0T

CCDs

PG of TPsdeterminesglobal zCMS

position of entire system

Reconstructed DCOPS & CSC Reconstructed DCOPS & CSC Positions and their PrecisionPositions and their Precision

Note: In this coordinate system the DCOPS are“up-side-down” (ME+2 DCOPS tops are at smaller zCMS)

zreco~ 270 m

Shimdelta

Newshim

Newshim

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Now, accuracy …

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Solid triangles: Reconstructed tops

of CSC Alignment pins

Solid triangles: Reconstructed tops of DCOPS boxes

First CCD pixels

Reconstructed positions of outer CSC PCB skins

B=0T

CCDs

PG of TPsdeterminesglobal zCMS

position of entire system

Accuracy check of ABSOLUTE Accuracy check of ABSOLUTE positions against PG at B=0Tpositions against PG at B=0T

Open triangles: PG measurement of tops of DCOPS boxes

Open triangles: PG meas. of

CSC Alignment pins

PG measurements of coded targets on outer CSC PCB skins

Reco and PG now match well !!!

Perfect !

(no PG avail.)

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Discrepancy in Z between Discrepancy in Z between PG and Fitted positionsPG and Fitted positions

683 micron

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Reconstruction of zReconstruction of zCMS CMS for for

CSCs in ME+2 SLM2-5 at B=4TCSCs in ME+2 SLM2-5 at B=4T

B=4T

B=0T fit positions

B=4T fitted CSC positions

Disk bending is reconstructed !This assumes (incorrectly) that the TP’s donot shift in z &do not rotate!

~ 13mm

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SummarySummary• Reconstruction of zCMS coordinate is working

• Z-resolution & Sensitivity to relative motion ≈ 60 m

• Z-precision of reconstructed CSC centers ≈ 270 m

• Z-accuracy of reconstruction ≈ 680 m (Comparison with Photogrammetry data) Accuracy required by design 1 mm

• Disk bending at B=4T is reconstructed

THANKS

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Back up slides

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ME+2 DiskME+2 Disk

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Beam Profiles measured with CCDs 2 & 4 Beam Profiles measured with CCDs 2 & 4 in ME+2 SLM2-5 for both Lasersin ME+2 SLM2-5 for both Lasers

Laser Beam Profiles supplied by Jim Bellinger

Pt.5Pt.2 One MTCC2 alignment event: Nov 3, 2006 00:01:16:48

CCDs 4

Laser 2

CCDs 2 in 10 DCOPS

Good hits !

Laser 2

Laser 5

Laser 5

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Reconstructing ABSOLUTE CSC Reconstructing ABSOLUTE CSC zzCMSCMS- coordinates via DCOPS geometry…- coordinates via DCOPS geometry…

z-coordinate of first CCD pixel(14 m/pixel × 1024 pixels)

z-reference surface for DCOPS dowel pin (new!)

nominal zCMS- position for SLM

updated CAD Drawing by Dave Eartly – 10/15/07

CCD

Top of DCOPS box

DCOPS foot

Dowel pin (precision element)center

AllowedLaser Range

CCDs2 & 4

All dimensions in mm

DCOPS Side View

+

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z-coordinate of first CCD pixel

z-reference surface for DCOPS dowel pin

nominal zCMS- position for SLMCCD

Top of DCOPS box z-coord. of PG Target on top of DCOPS box

Shim

Mounting plate

Mounting barDCOPS foot

top CSC PCB panel

updated CAD Drawing by Dave Eartly – 10/15/07

CSC z-reference surface for al. reco (new!)

coded PG target

lives here !

CSCframe

… … CSC geometry…CSC geometry…

38

.19

4

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……and Transfer Plate (TP) geometryand Transfer Plate (TP) geometry

TP ref. surface (also for PG)

SLM Reference DCOPS

Transfer Line DCOPS

Laser

6.73 (newly found shim !)

updated CAD Drawing by Dave Eartly – 10/17/07

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Sanity check on Precision as Sanity check on Precision as returned by Reconstructionreturned by Reconstruction

All errors in microns

All tolerancesIn this columnunder review !

Precision dominated by mechanical tolerances and not by spread of laser hits in fit (60 m res.) !

ok !

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Effect of missing hitsEffect of missing hits

This Example: Turn onegood hit into a bad hit on two separate DCOPS on the same chamber

Result:This has only a small effect on the overall fit and reconstructed positions !

Simulate effect of missing laser hits (e.g. due to shadowing) on the reco results by manually inflating errors on good hits

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Effect of missing hits cont’dEffect of missing hits cont’d

Chambers MEp2_2_08 MEp2_1_14 MEp2_2_08 MEp2_2_08

1 7 DCOPS included and 3 DCOPS excluded (Original positions) 8096.52 mm 8097.02 mm 8097.95 mm 8095.92 mm

Ids for forced bad hits Shifts in Measurement (mm) Error (micron) Shift (micron) Shift (micron) Shift (micron) Shift (micron)

2 ID 7 L 0 10000 0 0 0 0

3 ID 7 L 0 5000 0 0 0 0

4 ID 7 L 20 17 6170 4800 2370 2370

5 ID 7 L, 6 L 0 10000 30 -20 10 10

6 ID 7 L, 6 LR 0 10000 20 -20 10 10

7 ID 7 L, 6 LR, 16 LR 0 10000 10 880 -10 -10

8 ID 7 L, 6 LR, 16 LR, 17 UDLR 0 10000 -60 660 -50 -50

9 ID 7 LR, 6 LR, 16 LR, 17 UDLR 0 10000 -60 -40 -50 -50

10 ID 1-7 all Left CCDs 0 10000 -200 -140 -440 -440

11 Id 3 L (10 mm error) 0 10000 0 0 -190 -190