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The GlueX CDC

Straw Tube Chamber. Curtis A. Meyer Carnegie Mellon University. The GlueX CDC. Physics Requirements Chamber Specifications Prototype Construction Future Work Final Chamber Summary. Physics Requirements. protons. CDC+FDC. 10-60 o. CDC. ~1GeV/c. FDC. 99% Charged particle acceptance

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The GlueX CDC

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  1. Straw Tube Chamber Curtis A. Meyer Carnegie Mellon University The GlueX CDC Physics Requirements Chamber Specifications Prototype Construction Future Work Final Chamber Summary The Straw Tube Chamber

  2. Physics Requirements protons CDC+FDC 10-60o CDC ~1GeV/c FDC 99% Charged particle acceptance 98% Photon acceptance Momentum of tracks in the CDC p!1(1800)p ! 2+2-±p pions The Straw Tube Chamber

  3. Chamber Requirements To achieve the overall momentum and vertex goals of the experiment, the CDC needs to achieve: r» 150-200m z» 2mm Stereo Layers z=r/tan (st) » 1.4 mm Charge Division z» 1.5% (2L) » 6 cm Sweep time should be as short as possible ~600-700ns Electrostatics need to be very well understood and regular due to the large Lorentz Angle. Particle ID using dE/dx for p· 450 MeV/c (proton/ pion) The Straw Tube Chamber

  4. BNL EVA Chamber Scope based DAQ to Emulate FADC 2m long, 2cm diameter straw tube chamber from BNL. Electronic Gas mixing system The Straw Tube Chamber

  5. Simulations Detailed GARFIELD simulations have been carried out for the CDC, and information on a number of potential gas mixtures have been cataloged. Detailed Acceptance studies using HDFast have been carried out for the combined CDC FDC system, and show that for typical channels with exotic Hybrids, we have about 99% of 4 acceptance for charged tracks. A very detailed description of the CDC is in HDGEANT, but we have not written digitization routines yet. The Straw Tube Chamber

  6. Chamber Mechanics In order to fully combine both the FDC and CDC for tracking, the material in the downstream end-plate of the chamber needs to be minimal. Sense wires: ~3500 ~70 gm tension 245kg Straw tubes are sufficiently rigid to fully support this load. Straw tubes provide very uniform electric fields Garfield studies show that we can achieve the drift time limits. Guard wire option: ~14000 ~200 gm tension 2800kg Endplates and shells would need to be thick to support this! Probably more than 4 per sense wire to get a uniform field. Corners in the cells will produce large drift times. The Straw Tube Chamber

  7. Chamber Design Active length between 1.75m and 1.97m rmin = 14.0cm rmax=57.8cm Upstream endplate: 0.95 cm thick Al tooling plate Al donuts All electrical connections Down stream endplate: 0.50 to 0.60 cm thick Al or .90cm thick G10 Delrin donuts Possible termination circuits 23 Layers from 14cm to 59cm Layer 1-4 Straight Layer 5-6 +6± stereo Layer 7-8 -6± stereo Layer 9-13 Straight Layer 14-15 +6± stereo Layer 16-17 -6± stereo Layer 18-23 Straight Inner shell: Thin Carbon fiber – mostly protection Outer shell: Carbon fiber or fiberglass Alignment and protection 3250 Wires The Straw Tube Chamber

  8. Electronics 125MHz FADC Straw Tube Pre-Amp High Voltage t» 2-3ns time 8ns wide time bins FADC: IU/JLab Preamp: Alberta/JLab straw tube ADC yields dE/dx information JETSET: NIM A367, 248 (1995) dE/dx at 10% resolution in straw tubes. Need 10-bit ADC resolution Tracks The Straw Tube Chamber

  9. Resolution Contributions to Resolution 90-10 Ar-CO2 Geometrical Precision 40m Gravitational Sag 56m Timing Resolution 45m Electrostatic Deflection 10m Gas Diffusion 120m ________________________ Total » 145m We have a gas mixture that should work, but we would like to optimize this . Would like to use the same gas in both the FDC and the CDC. tmax» 0.5s Time [s] The Straw Tube Chamber Radius [cm]

  10. Gas Leaks A problem with straw tube chambers is that the glue joints leak. Designed, built and tested a feed through system that forms a solid glue seal. System has held several psi overpressure for nearly a year. Donut The Straw Tube Chamber

  11. Prototype Construction The difficult part of the straw-tube chambers are the 6± stereo layers. Every step involving these has been a challenge with its own problems to solve. Compound angles in machining of the endplates. Aligning tubes in the chambers. Gluing tubes together for structural support. Better Clamshell clamps will be needed for the final chamber. The Mylar tubes are quite delicate, while it appears that Kapton is more robust, but MORE expensive. The Straw Tube Chamber

  12. Stringing The Chamber Glue donut Cut to length Select tube Glue in chamber Magnetic Feeds Vertical stringing Pneumatic crimper The Straw Tube Chamber

  13. Prototype Construction The Straw Tube Chamber

  14. Prototype Testing 2004 2005 3rd 4th 1st 2nd 3rd 4th Chamber Assembly and Stringing High Voltage Tests Signal Tests Structural Tests Kapton Tubes Wire tensions are accurate and reproducible. We still need to do long-term stability tests. Mechanical Robustness tests will start as the chamber is taken off the stringing stand. We are close to being able to perform high-voltage and signal tests. The Straw Tube Chamber

  15. Final Chamber Machine Endplates in industry Acquire Shells Machine Al and Delrin Donuts Acquire Crimp pins Acquire Straw tubes Acquire Wire Parts need to be spec’d, ordered and checked. Tube building takes about 15 minutes per tube (1 person) Tube installation takes about 15 minutes per tube (2 people) Tube stringing takes about 15 minutes per tube (2 people) Electrical and gas hookup times are still not definitive. 3 to 3.5 year to build the final chamber The Straw Tube Chamber

  16. Summary The CDC together with the FDC forms a complete tracking package for the GlueX detector that covers roughly 99% of 4 . The most challenging construction detail of the chamber is the stereo layers. There are still some issues with aligning tubes that need better tools. Test Kapton tubes in prototype. Based on what we have seen with samples, these appear a better choice. Settle on final length based on Monte Carlo (175cm – 200cm), this has little or no impact on construction. The Straw Tube Chamber

  17. The Straw Tube Chamber

  18. Chamber Schedule Task Year 1 Year 2 Year 3 Tool Construction Design and Procure Endplates Acceptance Checks on plates Procurement of feed throughs Procurement of wires and pins Acceptance of parts Procurement of on-chamber electronics Tests of electronics Construction Setup Chamber Stringing Gas System Installation Electronics Installation Chamber Tests Delivery of Chamber Best estimate is 3.5 years from start of procurement to delivery Extra Manpower The Straw Tube Chamber

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