chiho wang trd conference duke university bari, sep. 2003 1 design and construction of the atlas...

Chiho Wang TRD ConferenceDuke University Bari, Sep. 2003

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Design and Construction of the

ATLAS Barrel TRT

Chiho WangDuke University


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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


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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


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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


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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


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Module End Plate Region


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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


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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


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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


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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


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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


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Carbon-Fiber Shell

Cooling Tubes

Structural support for module. Heat exchanger for module

cooling

Holes for Divider earsKapton

lamination


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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


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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


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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


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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.


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Laser alignment data


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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


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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


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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


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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


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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


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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


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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


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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


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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)


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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


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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


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X-ray system for signal test & gain mapping

Slides

RotationMounting

Ring

W targetX-ray Slit &

Cu foil filter

DAQ

Fe55


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Signal Test Example

Wire shorted across wire-joint

A normal channel but picking up noise from

the shorted wire


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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


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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.

chiho wang trd conference duke university bari, sep. 2003 1 design and construction of the atlas...

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