The Making of ATLAS Muon chambers @NIKHEF

Marcel Vreeswijk (NIKHEF)

• The NIKHEF Muon Mission• Drift tube wiring• Chamber assembly • X-ray scan of BOL-0 at CERN• Status and Plans

The Making of ATLAS The Making of ATLAS Muon chambersMuon chambers

@NIKHEF@NIKHEF

The Making of ATLAS The Making of ATLAS Muon chambersMuon chambers

@NIKHEF@NIKHEF


NIKHEF Muon Mission

West side has expansion length o 0.1m in Xras

•

s

Construct: 96 Barrel Outer Large (BOL) chambers

High Mechanical Precision: 20m RMS on wire positions

This talk: BOL-0 and Serial ProductionThis talk: BOL-0 and Serial Production

2m

5m

BOL=spacer+2x3 drift tube layers+ In-Plane alignment


Tube wiring + QC

•Drift tubes:•Extruded aluminum drift tubes (3cm)

•Wire (50m gold-plated tungsten) positioned by two end-plugs

QC on drift tubes, specs:•Wire position: |Z,Y|<25m •Wire tension=>frequency 27.2+-1.4 Hz, RMS<0.3Hz•Leak rate: <2.5 10-8 bl/s •HV check: <20nA @3500V

Endplug


QC-Wire position

Wire position Spec: |Y,Z|<25m

s

EndPlug

Drift Tube

Coil

Rejection <<1%:2 tubes with Z> 50um (1 checked: no twister)

cut cut

For BOL-1All tubes checked

In future: Fast pre-check endplug

No twisterto positionwire

RMS: ~6m


QC-Wire tension

Quality Control on drift tubes, specs:•Wire Frequency: 27.2 (+-1.4)Hz, RMS<0.3Hz

Rejection <<1%.

s

Horse-shoe magnet

Drift tube

Principle: Lorentz force on current through wire causes vibration

FrequencyRMS: 0.17 Hz

Tension re-measured just before gluing on table(checks creep + broken wires)


QC-Leak Rate + HVQuality Control •Leak rate: <2.5 10-8 bl/s•HV: < 20nA at 3400V

s

Drift tube (1% He) Vacuum chamber

HV

He sniffer

Principle:

Automated ‘Matrix’ for 80 tubes


Rejection 1% (!)

QC-Leak Rate

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3 tubes inspected:•1 physical hole in aluminum•2 ‘dust’ on O-ring

Leak rate is low:from 3bar to 2bartakes several years!!

10-6 bl/s

Leak-rate

spec


QC-HV• A typical ‘Matrix’ fillA typical ‘Matrix’ fill

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Tubbies: Leak current 30-5-2001, av. laatste 3 metingen

-0.5

0

0.5

1

1.5

2

2.5

3

3.5

4

4.5

0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80

nA

Gauge

Tube withexcess<<spec.Measure 5hrs. Average last 3hrs

Tube nr

Cur

rent

(nA

)

Current as function of time

0

1

2

3

4

5

6

30-05-0118:00

30-05-0119:12

30-05-0120:24

30-05-0121:36

30-05-0122:48

31-05-010:00

Date & Time

tub

e c

urr

en

t (n

A)

Tube A1

Tube A2


Chamber Assembly


• Spacer monitored by RASASSituation mid 2000

Sphere tower with changeable block to adapt to tube layers

NIKHEF Comb

Frascati comb

RASAStower

‘Ear’ with sphere and RASAS-MASK

In-plane mask

In-plane lens

Xplate

longbeam

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No Flexo


‘RASAS’ Monitors

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Monitor positioning during assembly by RASAS monitor:

Changeable blocks

Support ‘ear’ which holds the mask

The RASAS tower which holds the camera and lens

xplate

Block 1

Block 2

Block 3

Ypitch 26.011mm

Scatter 5um

Measured temperatures explain (small) drift

Marcel Vreeswijk (NIKHEF) s

Tube diameter 3cmDistance 65m

tube

tube tube

tubetube

Side rope Central rope

Gluing BOL-02 x glue units2x3 glue nozzles

•Tube layer 1 central ropes•Spacer glued on layer 1•Tube layer 2 central ropes•Spacer+1 glued on layer 2•Tube layer 3 central+side ropes•Spacer+1+2 on layer 3•etc….


Sag Compensation•

Sagcompen-sation tower

Additionalweight for balance

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•Own weight leads to large sag of xplates•Compensate (at Bessel points) with pneumatic system•Need typical P=3bar (8 towers) to carry chamber (150kg)

Residue:order 10m


Gluing BOL-0

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Glue: Days needed1 Glue Spacer1 1st layer+platforms1 spacer on 1st1 2nd layer+spacer4 layersTotal <10 days


The BOL-0

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The BOL-0 was mechanically

finished Dec 5th 2000

Next, studies:•X-ray scan


Test @CERN inTomograph


Test @CERN inTomograph

Wire positionsRMS 16m

Analysis of Martin Woudstra


Test stand

s

DATCHADATCHA

Like cosmic ray setup at CERN (shutdown in 2000)

Test of alignment principle with prototype muon sector,using cosmic tracks --> 10m on sagitta


Test stand @NIKHEF

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Tests five chambers using cosmic rays (end 2001)•Checks wire positions•Checks DCS + DAQ

Trigger modules, consisting of 50cm iron, with two layers scintillator. Ecut>1GeVExpected rate: 100Hz


Status and Plans

• Finished BOL-0 at NIKHEF (dec. 5th 2000) with high mechanical precision (16m RMS)

• Quality Control automated

• Production of tubes started May 2001

• Now: Produce first chamber

• Expect to finalize 10 chambers by end 2001

• Produce 1chamber/2weeks: 24 chambers/year -> finish summer 2005

• Late 2002, evaluate need to speed up chamber production (work weekends and/or two gluing steps/day)

• Cosmic ray setup operational end 2001


Sag Compensation• Xplate sag before and after

compensation

s

After sag adjustment we observe (almost) symmetric sags for chamber up and down positions-> no stress

Chamber up

Chamber (upside) down

Understoodwithin +-10m


Gluing BOL-0• RASAS monitors

SE

NW

SW

NE

Global Z,RASAS X

Global X

•Stability in Y appears good

•Relatively large Z movement layer 6 (spacer floats on glue?)

s

Lever arm in stacking block

Global Z

Global Y (up)


Temperature Stability

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•Aluminum expands 24um/ oC/m, Granite 7um/ oC/m

•Under normal conditions, temperature stable within +-0.4 oC

•Test case: increase temp. by 1 oC: check RASAS monitors

Xplate 2.4mfixed monitorgranite

Free toexpand

Raw: 50um

Correct for AL 24um/ oC/m

+ Correct for granite 7um/ oC/m


Assembly Station


• Granite table: 6m x 2.5m

•Three bare Cross-Plates are positioned on the station, carried by sphere holders•The combs which will support the tubes are also visible•In the background: wiring station, Quality Control

setup(s)

Situation mid 99

North X

East Z

Up Y

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Alignment


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Projective alignment

In-Plane

Relative measurement of three points. Accuracy 1 um

the coded mask~ 100um block size

•Alignment scheme:


RASNIK• Components provided by NIKHEF

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Light source + maskImage sensor

Lens + holder


ATLAS-Muon


• Magnet system: air core toroid,

• End cap toroid constructed in the Netherlands

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B field measurement by Hall probes (on CAN bus) designed and provided by NIKHEF

|BHall| - |Bcoil|

0.02%calibration


QC-Leak Rate

Quality Control on drift tubes, specs:•Leak rate: He (4 bar) 2.5 x 10-8 bl/s

s

Drift tube (1% He) Vacuum chamber

HV (future)

He sniffer

cut

Rejection 4%

Leak rate is low:from 4bar to 2bartakes several years!!


BOL-0Heat Studies (No flexoos in BOL-0)

s

Inplane

Yrasnik= 2 x sag

The BOL-0 was covered with heat blankets, producing 50W/m2

Gradient between MLs: 2.5 to 4 oCSag of Chamber: 200um 50 to 80 um/oC= acceptableSag of xplate: 25um 6 to 10 um/oC = acceptable

400um

Yrasnik= 2 x sag

Xplate

50um

Chamber sag

Xplate

sag

Documents

The Making of ATLAS Muon chambers @NIKHEF