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A Brief Introduction to the STAR Time Projection Chamber

A Brief Introduction to the STAR Time Projection Chamber. Jim Thomas Lawrence Berkeley National Laboratory June 4 th , 2009. The TPC Flies from LBL to BNL - Nov 6, 1997. In 2009, the FEE electronics was upgraded to TPX - see talk by T. Ljubicic. Basic Size and Shape. 4.2 m long

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A Brief Introduction to the STAR Time Projection Chamber

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  1. A Brief Introduction to the STAR Time Projection Chamber Jim Thomas Lawrence Berkeley National Laboratory June 4th, 2009

  2. The TPC Flies from LBL to BNL - Nov 6, 1997 In 2009, the FEE electronics was upgraded to TPX - see talk by T. Ljubicic

  3. Basic Size and Shape • 4.2 m long • 4 m dia • Cathode at midplane of TPC • 28 kV, norm • Readout on both ends • Anode planes, each with Inner & Outer sectors

  4. 60 cm 190 cm TPC Sector Detail • 24 sectors • 12 on each side • Large pads for good dE/dx resolution in the Outer sector • Small pads for good two track resolution in the inner sector See talk by Y. Fisyak

  5. Sector Repair is possible but not a trivial task Sector Installation & Tooling See talk by A. Lebedev

  6. TPC Sector Detail • Gating Grid • Ground Shield • Anode • 4 mm pitch, no field wires • Spacing: inner  outer • Pad Plane See talks by A. Lebedev and R. Witt

  7. A few other anode facts • There are 8 HV channels and 6 RDOs per sector • We can address anode wires by radius: on, off, or lower the gain • HV almost coincident with RDO divisions on the outer sector • HV not coincident with RDO division in the inner sector Gain Voltage

  8. Field Cage: to short or not to short … • The field cage operates at 28 kV … limit is ~ 40 kV • Occasionally we will find a short between a pair of the Field Cage rings • Usually (magnetic) dirt • We had one permanent short on the East end • Its has been repaired • We have an intermittent short on the west end • Approx ¼ of a 2 M resistor • After a cluster of Main Magnet crashes this year we developed a full short • Approx ring 130 (out of 182) We have precision software to deal with these shorts See talks by G. Van Buren & J. Seele

  9. Gas • STAR uses P10 • Low Drift Field • 130 V/cm • Good Diffusion • DV at Peak of Curve • Easy to mix • He-Ethane was considered as an option • Good Diffusion • Lower MCS • But DV is low and requires a higher field • STAR designed for 85 kV • Practical limit ~40 kV • Other gases may be possible but choices limited by drift field and BNL health & safety reqs

  10. Gas System The existing gas system works well and could be extended to include H2O or Alcohol. We have no experience with this and don’t know what impact it will have on the TPC and internal components.

  11. Summer Shutdown:usually a very tight schedule • STAR runs 24/7 for 20-30 weeks per year • Typical schedule for shutdown period • Not a lot of time for R&D … or repair

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