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1 Jim Thomas - LBL
2 Jim Thomas - LBL
A Brief Introduction to the STAR Time Projection Chamber Jim Thomas - - PowerPoint PPT Presentation
A Brief Introduction to the STAR Time Projection Chamber Jim Thomas - - PowerPoint PPT Presentation
A Brief Introduction to the STAR Time Projection Chamber Jim Thomas Lawrence Berkeley National Laboratory June 4 th , 2009 Jim Thomas - LBL 1 The TPC Flies from LBL to BNL - Nov 6, 1997 In 2009, the FEE electronics was upgraded to TPX - see
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SLIDE 3
3 Jim Thomas - LBL
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
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4 Jim Thomas - LBL
TPC Sector Detail
60 cm 190 cm
- 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
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5 Jim Thomas - LBL
Sector Repair is possible but not a trivial task
Sector Installation & Tooling See talk by A. Lebedev
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6 Jim Thomas - LBL
TPC Sector Detail
Sector Operation for 20:1 signal to noise Sector anode voltage gas gain inner 1170 3770 ± 10%
- uter
1390 1230 ± 10%
- Gating Grid
- Ground Shield
- Anode
– 4 mm pitch, no field wires – Spacing: inner ≠ outer
- Pad Plane
See talks by A. Lebedev and R. Witt
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7 Jim Thomas - LBL
A few other anode facts
- There are 8 HV channels and 6 RDOs
per sector
– We can address anode wires by radius:
- n, 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
0.1 1 1050 1150 1250 1350 Inner Outer
Gain Voltage
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8 Jim Thomas - LBL
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
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9 Jim Thomas - LBL
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
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10 Jim Thomas - LBL
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.
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11 Jim Thomas - LBL
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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12 Jim Thomas - LBL
TPC Review 2006
- Charge
– The review panel is asked to assess the ability of the STAR TPC, including planned upgrades of its front end electronics and readout, to meet the physics driven requirements of the experimental program in the high luminosity era at RHIC.
Distortions - Pile up – Aging - R&D - Support for operations
- Main Conclusions
– [The TPC] will clearly remain the main tracking detector in STAR for the foreseeable future. The committee notes that RHIC has achieved continued luminosity improvements to within about a factor five of the maximum instantaneous luminosity ultimately envisioned for RHIC II. – In summary, the committee believes that the TPC can be
- perated and produce excellent physics results at the projected
higher luminosities. Solving the problems of distortions and pileup continue to pose a challenge, but there appear to be no problems in principle to prevent success. See: http://indico.mppmu.mpg.de/indico/conferenceDisplay.py?confId=494 for a link to the 2006 presentations and the final report of the committee
Password: star2009
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13 Jim Thomas - LBL
BNL Science and Technology Review – Summer ‘08
- The ‘08 review panel asked us to look at high luminosity running at RHIC
– The STAR collaboration should develop a program to study possible consequences (e.g., aging) of operating the TPC in a high luminosity
- environment. Progress should be documented and presented at the 2009
RHIC S&T review.
- Nu Xu has asked you to help us address the long term future of the TPC
- Charge