The NIKHEF Muon Mission

1
The Making of ATLAS Muon chambers_at_NIKHEF

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

2
NIKHEF Muon Mission

BOLspacer2x3 drift tube layers In-Plane
alignment
Construct 96 Barrel Outer Large (BOL)
chambers High Mechanical Precision 20mm RMS on
wire positions This talk BOL-0 and Serial
Production
West side has expansion length o 0.1m in Xras
s
3
Tube wiring QC

• Drift tubes
• Extruded aluminum drift tubes (3cm)
• Wire (50mm gold-plated tungsten) positioned
  by two end-plugs

Endplug

• QC on drift tubes, specs
• Wire position Z,Ylt25mm
• Wire tensiongt
• frequency 27.2-1.4 Hz, RMSlt0.3Hz
• Leak rate lt2.5 10-8 bl/s
• HV check lt20nA _at_3500V

4
QC-Wire position
Wire position Spec Y,Zlt25mm
For BOL-1 All tubes checked In future Fast
pre-check endplug
Rejection ltlt1 2 tubes with Zgt 50um (1
checked no twister)
cut
cut
No twister to position wire
s
5
QC-Wire tension

• Quality Control on drift tubes, specs
• Wire Frequency 27.2 (-1.4)Hz, RMSlt0.3Hz

Principle Lorentz force on current through wire
causes vibration
Drift tube
Frequency RMS 0.17 Hz
Horse-shoe magnet
Tension re-measured just before gluing on
table (checks creep broken wires)
Rejection ltlt1.
s
6
QC-Leak Rate HV

• Quality Control
• Leak rate lt2.5 10-8 bl/s
• HV lt 20nA at 3400V

Principle
HV
Drift tube (1 He)
Vacuum chamber
He sniffer
Automated Matrix for 80 tubes
s
7
QC-Leak Rate
Leak-rate
Leak rate is low from 3bar to 2bar takes several
years!!
Rejection 1 (!)
10-6 mbl/s

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

s
8
QC-HV

• A typical Matrix fill

Tube with excessltltspec.
Measure 5hrs. Average last 3hrs
Current (nA)
Gauge
Tube nr
s
9
Chamber Assembly

• Spacer monitored by RASAS

Situation mid 2000
No Flexo
In-plane lens
NIKHEF Comb
longbeam
RASAS tower
Xplate
In-plane mask
Frascati comb
Ear with sphere and RASAS-MASK
Sphere tower with changeable block to adapt to
tube layers
West side has expansion length o 0.1m in Xras
s
10
RASAS Monitors

Monitor positioning during assembly by RASAS
monitor
Support ear which holds the mask
xplate
Changeable blocks
The RASAS tower which holds the camera and lens
Measured temperatures explain (small) drift
s
11
Gluing BOL-0
Tube diameter 3cm Distance 65mm
2 x glue units 2x3 glue nozzles
Side rope
Central rope

• Tube layer 1 central ropes
• Spacer glued on layer 1
• Tube layer 2 central ropes
• Spacer1 glued on layer 2
• Tube layer 3 centralside ropes
• Spacer12 on layer 3
• etc.

s
12
Sag Compensation

Residue order 10mm

• Own weight leads to large sag of xplates
• Compensate (at Bessel points) with pneumatic
  system
• Need typical P3bar (8 towers) to carry chamber
  (150kg)

s
13
Gluing BOL-0
Glue Days needed 1 Glue Spacer 1 1st
layerplatforms 1 spacer on 1st 1 2nd
layerspacer 4 layers Total lt10 days
s
14
The BOL-0

• The BOL-0 was mechanically
• finished Dec 5th 2000
• Next, studies
• X-ray scan

s
15
Test _at_CERN inTomograph
s
16
Test _at_CERN inTomograph
Analysis of Martin Woudstra
Wire positions RMS 16mm
s
17
Test stand
Like cosmic ray setup at CERN (shutdown in 2000)

• DATCHA

Test of alignment principle with prototype muon
sector, using cosmic tracks --gt 10mm on
sagitta
s
18
Test stand _at_NIKHEF

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

Trigger modules, consisting of 50cm iron, with
two layers scintillator. Ecutgt1GeV Expected rate
100Hz
s
19
Status and Plans

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

20
Sag Compensation

• Xplate sag before and after compensation

Chamber up
Chamber (upside) down
Understood within -10mm
After sag adjustment we observe (almost)
symmetric sags for chamber up and down
positions-gt no stress
s
21
Gluing BOL-0

• RASAS monitors

Global Z

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

Lever arm in stacking block
Global Y (up)

• Stability in Y appears good

s
22
Temperature Stability

• 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

Free to expand
monitor
granite
Raw 50um
Correct for AL 24um/ oC/m
Correct for granite 7um/ oC/m
s
23
Assembly Station

• Granite table 6m x 2.5m

Situation mid 99
East Z
Up Y
North X

• 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)

West side has expansion length o 0.1m in Xras
s
24
Alignment
the coded mask 100um block size

• Alignment scheme

West side has expansion length o 0.1m in Xras
s
25
RASNIK

• Components provided by NIKHEF

Image sensor
Light source mask
Lens holder
s
26
ATLAS-Muon

• Magnet system air core toroid,
• End cap toroid constructed in the Netherlands

B field measurement by Hall probes (on CAN bus)
designed and provided by NIKHEF
West side has expansion length o 0.1m in Xras
s
27
QC-Leak Rate

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

HV (future)
Drift tube (1 He)
Vacuum chamber
He sniffer
Leak rate is low from 4bar to 2bar takes several
years!!
cut
Rejection 4
s
28
BOL-0
Heat Studies (No flexoos in BOL-0)
The BOL-0 was covered with heat blankets,
producing 50W/m2
Inplane
Yrasnik 2 x sag
Gradient between MLs 2.5 to 4 oC Sag of Chamber
200um ? 50 to 80 um/oC acceptable Sag of
xplate 25um ? 6 to 10 um/oC acceptable
s