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Electron Detector for the Hall C Compton Polarimeter

Electron Detector for the Hall C Compton Polarimeter. J.W. Martin & D. Dutta U. Winnipeg & Mississippi State U. Tasks List from Previous Meeting. 7/25/06. Decide technology ASAP Base decision on: rates (signal and background) granularity (guess similar to Hall A and Mainz?)

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Electron Detector for the Hall C Compton Polarimeter

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  1. Electron Detector for theHall C Compton Polarimeter J.W. Martin & D. Dutta U. Winnipeg & Mississippi State U

  2. Tasks List from Previous Meeting 7/25/06 • Decide technology ASAP • Base decision on: • rates (signal and background) • granularity (guess similar to Hall A and Mainz?) • fiducializability? • Current favorite: …? Input from collaboration/experts? • Begin detailed budgeting for upcoming grant cycles • NSERC: deadline end of Oct. • DOE: deadline Nov. • Need ideas on how to split tasks (MSU vs. UWpg/Canadians) • Detailed simulations – decide position wrt chicane dipoles. • Prototyping • Receive funding • Build it

  3. Technology Selected: CVD Diamond Strip Detector • Lets examine why? Low leakage current, shot noise Fast signal collection Low capacitance, noise Radiation hardness Smaller signal Thanks R. Wallny (UCLA)

  4. Technology Selected: CVD Diamond Strip Detector • Operation of Diamond Detectors • ~250 V bias voltage for 250 micron det. • (1V/micron) • Charged particle generates e-h pair, • Which drift apart in E-field to collecting • electrodes. • Detect the charge pulses (AC-coupled • detectors): Fast, low noise • Or measure induced current (DC-couples • radiation sensors): ~pA noise • Charge collection in diamonds: • Signal limited by impurities and grain • boundaries • Increases with E-field up to ~1V/mm • Charge collection distance ~ 250 micron • in poly-crystal diamonds, longer in single • crystal. Thanks H. Kagan (Ohio State)

  5. Radiation Hardness of Diamond Detectors Performance after irradiation with protons • Little change in S/N after • exposure of ~5 Mrad • 15% change in S/N after an • exposure of ~50 Mrad • Si 50% change in S/N after • exposure of ~3 Mrad. Thanks R. Wallny (UCLA)

  6. A pCVD Detector is Operational at BaBar (as BLM) Diamond detector in BaBar used to protect the Si vertex detector Thanks R. Wallny (UCLA)

  7. A Working Diamond Strip Detector Thanks R. Wallny (UCLA)

  8. Current Vendors • Element Six (UK based, subsidiary of de Beers, S. Africa) (2.1x2.1 cm2 one of their standard sizes, most used vendor) • Advanced Diamond Solutions ( US based) (relatively new, supplied to LANL and NSCL (MSU), quoted the highest price) • Sumitomo Semiconductors (Japan/US based)

  9. From Diamond to Detector • Nasty acid bath to clean off bits. • Metallization with Ti/Au or Cr/Au, etc. • Photolithography to etch strips • or shadow mask in metallization stage • Fabricate carrier board • Glue detector to board • Wirebond detector strips to strips on board Once this is done, we can think about reading the thing out with “standard” silicon electronics.

  10. Lithography & Metallization Options (including, wire bonding and making carrier boards) • U. of Manitoba (EE) complete nanofabrication laboratory, lots of experience with silicon, RF systems, board design – cost is nominal, but we must supply/train manpower. • Ohio State Univ (Harris Kagan, HEP) part of CERN RD42 Group, original developers of the detector tech, promises to do small jobs as ours for free. NSFL director Cyrus Shafai giving tour to UWinnipeg students Dec. 2006. (clean room seen behind) Sample preparation (acid bath and metallization) for diamond discussed with and ok’ed by Shafai (based on Phy. Stat. Sol. paper)

  11. Readout Electronics • Electronics chain: • Preamp • Discriminator • Fast logic/trigger generation • Digital I/O • Result: a “strip map” on an event-by-event basis • Use Hall A (French) Electronics • Custom design by TRIUMF (or build based on French design) • LHC (ATLAS) Electronics Options

  12. HALL-C Schematic 4 staggered Planes of 2.1x2.1 cm2 CVD diamond crystals ~250-500mm thick 100-150 micron pitch. 2 planes + motion mechanism to be built by Winnipeg, U. Manitoba & TRIUMF 2 planes to be build by MSU

  13. Funding Requests D. Dutta to DOE for $75,000 to build 2 planes J.W. Martin et al. to NSERC for $110,000 CAD for 2 planes and motion mechanism

  14. NSERC budget table

  15. Progress on simulations(D. Storey, UWinnipeg undergrad)(based on work of R. Jones et al) 4th dipole scattered electron e- det Strip map for Compton events 210 m strips • Compton x-sect and asym found to be in working order • electron det can now move upstream of 4th dipole • plan to investigate systematic effects (backgrounds, calibration, granularity) in Geant  det

  16. Status • DOE decision: March • NSERC: • “Large projects day” Feb. 5 defend proposal at NSERC HQ in Ottawa in front of “grant selection committee”. • April 1 decision. • Simulations: ongoing (D. Storey senior thesis) • Prototyping: Jeff would love to start immediately, but needs more manpower. • Peiqing Wang (UM) PhD student, but must complete Masters thesis (toroid field mapping) before beginning on this project.

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