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Qweak Collaboration Meeting Report on Drift Chamber Prototype I Testing (Oct 2005)

This report summarizes the Qweak collaboration's findings from the October 2005 meeting, focusing on Prototype I of the drift chamber. The prototype dimensions are 40cm x 40cm, equipped with gold-plated tungsten sense wires and beryllium-copper field wires. Key challenges included resolving oscillations caused by TDC feedback, resulting in various modifications such as shielding and capacitors. Continued testing involved different gas mixtures, voltage studies to optimize drift velocity, and initial designs for a new multi-chamber system aimed at enhancing detection efficiency.

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Qweak Collaboration Meeting Report on Drift Chamber Prototype I Testing (Oct 2005)

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  1. Region 2 Drift Chambers Status Report Qweak Collaboration Meeting October 2005

  2. Prototype I 40cm X 40cm 32 20mm Gold-plated Tungsten Sense Wires 33 100mm Gold-plated Beryllium-copper Wires

  3. Prototype I Test Setup

  4. Hurdles Jumped • TDC readout using MIDAS DAQ • “Feedback” from TDC ribbon cables to the chamber wires caused oscillations at ~22MHz. - Tried shielding the ribbon cables (no luck) - installed filter capacitors on the amplifier input (allowed us to take data but reduced amplifier sensitivity) - Wrapped the chamber with Aluminized mylar (Now operating without filter capacitors. Aluminum shield reduces feedback to below 30mV Threshold level) • Noise when DAQ running - Raised threshold to 50mV level

  5. Prototype I Tests • 10% CO2 90% argon gas • Nanometrics N-277 Amplifier/Discriminator cards • Threshold set at 1.5mamp (50mV) • Scintillators above and below chamber • Efficiency = (# events with at least one hit)/(# 3-fold scint. triggers)

  6. Cathode at –2000V

  7. Singles Rate

  8. Garfield Equipotential Lines (1800V)

  9. Garfield electron arrival times (1800V)

  10. # of hits/event Prototype I Events

  11. hits

  12. hits

  13. Continuing Tests • Voltage studies (Cathode/Field) to obtain optimum drift velocity and efficiency • Garfield simulations • Different gases (Argon/CO2/CF4)(Argon/Ethane)? • Mapping of active area to check uniformity

  14. Proposed New chamber

  15. New chamber

  16. Design Parameters • Four chambers with six planes each • Wire pitch 4.6 mm • 20mm gold-plated Tungsten sense wires • 75mm gold-plated Be-Cu field wires • 1664 electronics channels Nanometrics preamp/descriminators 100 x 16 channels/board = ~$35k

  17. Plans for 2006 • Build and test a chamber with the final dimensions xuv sense planes four cathode planes 208 electronics channels

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