Chiho Wang TRD Conference Duke University Bari, Sep Design and Construction of the ATLAS Barrel TRT Chiho Wang Duke University

Chiho Wang TRD Conference Duke University Bari, Sep Design Parameters  Straw based tracking chamber with TR capability for electron identification.  Straws run in parallel to beam line.  Active gas is Xe/CO 2 /O 2 (70/27/3) operated at ~2x10 4 gas gain  Counting rate ~ 6-18 MHz at LHC design luminosity cm -2 s -1

Chiho Wang TRD Conference Duke University Bari, Sep 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 Length1.5 m Sense Wire Length2 x 0.75 m Straw Diameter4 mm Wire Diameter30 um Distance between straws6.8 mm High Voltage Grouping8 straws

Chiho Wang TRD Conference Duke University Bari, Sep Type 1Type 2Type 3 Number of Modules32 Straws per Module Straw Layer Number Inner Radius (mm) Outer Radius (mm)  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 Conference Duke University Bari, Sep 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 SupportWire JointWire Support Regular Wires Single Joint Inner Wires Double Joint

Chiho Wang TRD Conference Duke University Bari, Sep Module End Plate Region

Chiho Wang TRD Conference Duke University Bari, Sep 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 Conference Duke University Bari, Sep 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) u Fast n: 4x10 14 cm -2 (20 LHC years) u Slow n: 1.7x10 15 cm -2 (30 LHC years)  Anode ageing was tested to withstand: u 18 C/cm (20 LHC year) Enforcement carbon-fiber bundle

Chiho Wang TRD Conference Duke University Bari, Sep Wire & Wire Joint  Wire:  30 ± 0.3  m gold plated tungsten wire  Wire joint: u Glass capillary tube: Length: 6mm OD: 250 um ID: 125 um u Melted at center to isolate 2 wire segments u Insert wire segments. u Sliding torches fuse glass to wire segments u Stronger than wire itself Torch Glass Holder Center-melt Wire/Glass fusion

Chiho Wang TRD Conference Duke University Bari, Sep Radiator  Stacks of polypropylene fiber sheets  Fiber is 15  m diameter  Packed to 66 mg/cm 3 density  Somewhat oriented and orthogonal to incident particle 200u m Optimal TR threshold Fiber Foil

Chiho Wang TRD Conference Duke University Bari, Sep 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 Conference Duke University Bari, Sep Carbon-Fiber Shell Cooling Tubes  Structural support for module.  Heat exchanger for module cooling Holes for Divider ears Kapton lamination

Chiho Wang TRD Conference Duke University Bari, Sep High Voltage Plate  Made of 3 parts: u Precision machined FR4 tray u Kapton circuit in the back u 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 Conference Duke University Bari, Sep Tension Plate  Double sided PC board u Holds wire tension u Connect wires to electronics u House gas fittings for gas system Gas fitting

Chiho Wang TRD Conference Duke University Bari, Sep Small Parts Twister Mid-Wire Support Taper Pin Eyelet 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 Conference Duke University Bari, Sep Construction of Barrel Modules  Starts with checking alignment elements u Shell, HV plates, Dividers are pre-assembled in the calibrated assembly frame on optical table. u 9 fiducial straws inserted, and their straightness along the module measured with laser alignment system.

Chiho Wang TRD Conference Duke University Bari, Sep Laser alignment data

Chiho Wang TRD Conference Duke University Bari, Sep 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 Conference Duke University Bari, Sep Insert Straws  Use straw insertion bullet: u Guide straws through holes in HV plate, radiator & divider u Protect straw re-enforcement carbon fiber strips from de-lamination  To avoid deforming radiator: u Spiral insertion sequence, from center outward u Alternate insertion direction every straw  After insertion u Test Individual straw group to 2.5kV Mylar Sleeve Delrin Head Short straw buffer

Chiho Wang TRD Conference Duke University Bari, Sep 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 sideAfter gluing both sides A ring of Conductive glue Rotor End plug holder Glue dispenser End Plug

Chiho Wang TRD Conference Duke University Bari, Sep 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 ” plastic syringe tip Glue Divider

Chiho Wang TRD Conference Duke University Bari, Sep End of “Mechanical Assembly”  Clean up: u Check cooling tube holes with gauge rod (rim/clean as needed). u Clean capacitor socket for blockage u Clean excessive glue on HV plate walls u Clean gas fitting seats on HV plate  Check: u HV test (last at 2.5kV): 2.5kV through each individual straw group u Module leak test: < 1 mBar / Bar / min Leak test system HV Relay box Gas seal plate & fitting for leak test HV Tester

Chiho Wang TRD Conference Duke University Bari, Sep Assemble/Attach Tension Plate  Tension plate assembly: u Thousands of components assembled each plate = thousands of possible leak Eyelets, Sockets, Capacitor barrels, Gas fittings. u 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 Conference Duke University Bari, Sep Stringing Sense Wire  Prepare sense wire u Pre-set sense wire length for wire joint positioning in the straw.  Stringing process u Blow a lead wire through straw. u Tie lead wire with sense wire (a knot) u Pull sense wire into straw through an ultra-sound cleaner u Apply weight and pin wire on eyelet Motorized Lead Wire Spool Air 60 gm 65 gm Crimp on wire length setting anchor Preset length Wire Joint Stop Ultrasound bath Weight applying pulley Lead Wire Air Wire Spool

Chiho Wang TRD Conference Duke University Bari, Sep Tension Measurement & HV Test  While stringing u Measure wire tension. u Re-string if out of range (55gm-85gm).  After stringing u HV test 1700V each wire u Re-string if failed or drawing > 10  A  Rework until all wires pass HV & tension requirements. Ultrasound bath Speaker DAQ Electronics Wire natural resonant frequency scan

Chiho Wang TRD Conference Duke University Bari, Sep Mobile16-Channel Tension Tester Front side Back side  After re-work u Measure wire tensions on both sides. u Re-work if low tension (<50gm ) u Re-work if |front – back| > 5gm (wire joint hits mid-wire support)

Chiho Wang TRD Conference Duke University Bari, Sep Finishing Up Module Conductive gluing ground 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 Conference Duke University Bari, Sep Module Passport Verification  On X-ray Scanner u Signal test: to ensure every channel functional, or documented if otherwise. u Gain map: 25 positions each wire segment. Gain variation < 5% or documented u HV soaking during signal test & gain mapping (2-3 days) identifies/remove unstable wires & record current draw u 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 Conference Duke University Bari, Sep X-ray system for signal test & gain mapping Slides Rotation Mounting Ring W target X-ray Slit & Cu foil filter DAQ Fe55

Chiho Wang TRD Conference Duke University Bari, Sep Signal Test Example Wire shorted across wire-joint A normal channel but picking up noise from the shorted wire

Chiho Wang TRD Conference Duke University Bari, Sep Gain Mapping Examples FrontBackFrontBack FrontBackFrontBack Low gain point Dirty wire High gain point between 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

Chiho Wang TRD Conference Duke University Bari, Sep 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.