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Chiho Wang TRD ConferenceDuke University Bari, Sep. 2003
1
Design and Construction of the
ATLAS Barrel TRT
Chiho WangDuke University
Chiho Wang TRD ConferenceDuke University Bari, Sep. 2003
2
Design Parameters
Straw based tracking chamber with TR capability for electron identification.
Straws run in parallel to beam line. Active gas is Xe/CO2/O2 (70/27/3) operated
at ~2x104 gas gain Counting rate ~ 6-18 MHz at LHC design
luminosity 1034 cm-2s-1
Chiho Wang TRD ConferenceDuke University Bari, Sep. 2003
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Design is modular for: reduced risk distributed production
to multiple sites
Basic Design of the Module:
Straws are embedded in Radiators and supported by Dividers and Endplates which are connected across the module by a carbon-fiber shell
Module Length 1.5 m
Sense Wire Length 2 x 0.75 m
Straw Diameter 4 mm
Wire Diameter 30 um
Distance between straws 6.8 mm
High Voltage Grouping 8 straws
Chiho Wang TRD ConferenceDuke University Bari, Sep. 2003
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Type 1 Type 2 Type 3
Number of Modules 32 32 32
Straws per Module 329 520 793
Straw Layer Number 19 24 30
Inner Radius (mm) 560 697 864
Outer Radius (mm) 697 864 1070
Entire barrel is divided into 3 rings of 32 modules.
Straws are distributed for a Continuous tracking geometry
52,544 straws, 105,088 readout channels
Average Number of straws crossed by a track = 36, out of 73 layers
Average number of TR-hits for 20GeV Pt electron = 7
Chiho Wang TRD ConferenceDuke University Bari, Sep. 2003
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Splitting the Wires
Sense wires are split in half to reduce counting rate. This is not enough for the 11 inner most layers of wires! ±40cm from the center of these wires are deadened by using 2 wire joints. All straws are the same, but there are 2 different kinds of wires: “Single
joint” & “Double Joint”
80cm
Wire Joint Wire Joint
Wire Support Wire Joint Wire SupportWire Support
Regular WiresSingle Joint
Inner WiresDouble Joint
Chiho Wang TRD ConferenceDuke University Bari, Sep. 2003
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Module End Plate Region
Chiho Wang TRD ConferenceDuke University Bari, Sep. 2003
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Components
Every component has its own QC process to go through when received from manufacturer, or when it’s prepared (pre-assembled) for installation
Chiho Wang TRD ConferenceDuke University Bari, Sep. 2003
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Straws
Straw is made by spirally winding and fusing 2 bands of aluminized kapton.
The aluminized surface is protected by carbon-polyimide coating.
Outside surface of straw is laminated with 4 bundles of carbon-fiber filament to improve electrical/thermal conductivity and mechanical strength.
Straw material has been tested in for radiation hardness in nuclear reactor up to :
: 800kGy (100 LHC years) Fast n: 4x1014 cm-2 (20 LHC years) Slow n: 1.7x1015 cm-2 (30 LHC years)
Anode ageing was tested to withstand: 18 C/cm (20 LHC year)
Enforcement carbon-fiber
bundle
Chiho Wang TRD ConferenceDuke University Bari, Sep. 2003
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Wire & Wire Joint
Wire: 30 ± 0.3 m gold plated tungsten
wire
Wire joint: Glass capillary tube:
Length: 6mm OD: 250 um ID: 125 um
Melted at center to isolate 2 wire segments
Insert wire segments. Sliding torches fuse glass to wire
segments Stronger than wire itselfTorch
Glass
Holder
Center-melt
Wire/Glass fusion
Chiho Wang TRD ConferenceDuke University Bari, Sep. 2003
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Radiator
Stacks of polypropylene fiber sheets
Fiber is 15 m diameter Packed to 66 mg/cm3 density Somewhat oriented and
orthogonal to incident particle
200um
Optimal TR threshold
Fiber
Foil
Chiho Wang TRD ConferenceDuke University Bari, Sep. 2003
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Divider & Radiator patterns
Kapton-foam sandwich Align straws along module every 25 cm
“Divider Ear”Fixation hole to assembly frame.
Trimmed off later
Chiho Wang TRD ConferenceDuke University Bari, Sep. 2003
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Carbon-Fiber Shell
Cooling Tubes
Structural support for module. Heat exchanger for module
cooling
Holes for Divider earsKapton
lamination
Chiho Wang TRD ConferenceDuke University Bari, Sep. 2003
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High Voltage Plate
Made of 3 parts: Precision machined FR4 tray Kapton circuit in the back Thin HV circuit pattern in the front
Bring HV to straws Position straws in the module Mount module to support structure Individual traces tested to 3kV
Chiho Wang TRD ConferenceDuke University Bari, Sep. 2003
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Tension Plate
Double sided PC board Holds wire tension Connect wires to electronics House gas fittings for gas system
Gas fitting
Chiho Wang TRD ConferenceDuke University Bari, Sep. 2003
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Small Parts
Twister
Mid-Wire Support
Taper PinEyelet
End Plug•Center wires at the end of the straw•Electrically connect inside and outside of a straw through conductive glue
•Centers wire at middle of the straw
•Wire fixation on tension plate
Capacitor Barrel
•Isolate capacitor from gas volume so that it can be replaced•Partially transfer wire tension from Tension plate to HV plate
Chiho Wang TRD ConferenceDuke University Bari, Sep. 2003
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Construction of Barrel Modules
Starts with checking alignment elements Shell, HV plates, Dividers are pre-assembled in the
calibrated assembly frame on optical table. 9 fiducial straws inserted, and their straightness
along the module measured with laser alignment system.
Chiho Wang TRD ConferenceDuke University Bari, Sep. 2003
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Laser alignment data
Chiho Wang TRD ConferenceDuke University Bari, Sep. 2003
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Insert Radiator + Divider into shell & attach HV plate
Assembly Frame
Alignment Rods
Divider Fixation
Pins
3kV tested between HV plate & Shell
Radiator
Guiding Platform
Chiho Wang TRD ConferenceDuke University Bari, Sep. 2003
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Insert Straws
Use straw insertion bullet: Guide straws through holes in HV
plate, radiator & divider Protect straw re-enforcement carbon
fiber strips from de-lamination To avoid deforming radiator:
Spiral insertion sequence, from center outward
Alternate insertion direction every straw
After insertion Test Individual straw group to 2.5kV
MylarSleeve
Delrin Head
Short straw buffer
Chiho Wang TRD ConferenceDuke University Bari, Sep. 2003
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Conductive Glue
Use endplug to glue straws from inside to outside and to HV plate
Measure straw resistance after gluing each side
HV test each straw group to 2.5kV before and after gluing each side
After gluing one side After gluing both sides
A ring of Conductive glue
Rotor
End plugholder
Glue dispenser
End Plug
Chiho Wang TRD ConferenceDuke University Bari, Sep. 2003
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Seal between High Voltage Plate and Straws
Seal around straw end-plug and HV plate surface with AY103
Pot back side of HV plate 2.4 mm thick with Stycast 1266.
3” plastic syringe tip
Glue Divider
Chiho Wang TRD ConferenceDuke University Bari, Sep. 2003
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End of “Mechanical Assembly”
Clean up: Check cooling tube holes
with gauge rod (rim/clean as needed).
Clean capacitor socket for blockage
Clean excessive glue on HV plate walls
Clean gas fitting seats on HV plate
Check: HV test (last at 2.5kV):
2.5kV through each individual straw group
Module leak test: < 1 mBar / Bar / min
Leak test system
HV Relay box
Gas seal plate & fittingfor leak test
HV Tester
Chiho Wang TRD ConferenceDuke University Bari, Sep. 2003
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Assemble/Attach Tension Plate
Tension plate assembly: Thousands of components
assembled each plate = thousands of possible leak
Eyelets, Sockets, Capacitor barrels, Gas fittings.
Seal inner surface with a layer of glue (AY103) for gas tightness
After tension plate attached, check HV paths continuity between Kapton traces and Capacitor pins.
HV trace
Capacitor barrel pin
Chiho Wang TRD ConferenceDuke University Bari, Sep. 2003
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Stringing Sense Wire
Prepare sense wire Pre-set sense wire length
for wire joint positioning in the straw.
Stringing process Blow a lead wire through
straw. Tie lead wire with sense
wire (a knot) Pull sense wire into straw
through an ultra-sound cleaner
Apply weight and pin wire on eyelet
Motorized Lead Wire
Spool
Air
60 gm
65 gm
Crimp on wire length setting
anchor
Presetlength
Wire JointStop
Ultrasoundbath
Weightapplying
pulley
Lead Wire
Air
Wire Spool
Chiho Wang TRD ConferenceDuke University Bari, Sep. 2003
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Tension Measurement & HV Test
While stringing Measure wire tension. Re-string if out of range
(55gm-85gm) .
After stringing HV test 1700V each wire Re-string if failed or
drawing > 10 A
Rework until all wires pass HV & tension requirements.
Ultrasoundbath
SpeakerDAQElectronics
Wire naturalresonant
frequency scan
Chiho Wang TRD ConferenceDuke University Bari, Sep. 2003
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Mobile16-Channel Tension Tester
Front side
Back side
After re-work Measure wire tensions
on both sides. Re-work if low tension
(<50gm ) Re-work if |front – back|
> 5gm (wire joint hits mid-wire
support)
Chiho Wang TRD ConferenceDuke University Bari, Sep. 2003
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Finishing Up Module
Conductive gluingground wire to
shell
Solder Ground wire To tension plate ground
Seal taper pin/eyelet
Seal tension plate edge to HV plate
Ground Wire
Seal Shell holes with Kapton disks
Chiho Wang TRD ConferenceDuke University Bari, Sep. 2003
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Module Passport Verification
On X-ray Scanner Signal test: to ensure
every channel functional, or documented if otherwise.
Gain map: 25 positions each wire segment. Gain variation < 5% or documented
HV soaking during signal test & gain mapping (2-3 days) identifies/remove unstable wires & record current draw
Re-work wires if removed wires > 1%.
Measure ionization volume leak rate Measure purging volume leak rate Measure wire tensions. Check Dimension & Envelope Test module mounting
Chiho Wang TRD ConferenceDuke University Bari, Sep. 2003
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X-ray system for signal test & gain mapping
Slides
RotationMounting
Ring
W targetX-ray Slit &
Cu foil filter
DAQ
Fe55
Chiho Wang TRD ConferenceDuke University Bari, Sep. 2003
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Signal Test Example
Wire shorted across wire-joint
A normal channel but picking up noise from
the shorted wire
Chiho Wang TRD ConferenceDuke University Bari, Sep. 2003
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Gain Mapping Examples
Front Back Front Back
Front BackFront Back
Low gain pointDirty wire
High gain pointbetween dividers
Bent straw
High gain point at wire end Wire hung at mid twister
High gain point at wire end Wire hung at end plug twister
G/G > 8% wires require action
No Action
Remove wire
Replace wire
Replace wire
Chiho Wang TRD ConferenceDuke University Bari, Sep. 2003
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Summary
QC procedures are in every step of production procedures. A QC “passport” is generated before a module leaves
production site. Module production is near its completion. ~ 10 modules have
been completed and shipped to CERN in the past month or so. In early 2004, modules will begin to assemble into barrel
support structure.
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