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

Tasks List from Previous Meeting 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 7/25/06

Technology Selected: CVD Diamond Strip Detector Lets examine why? SiliconDiamond Band Gap (eV) Electron/Hole mobility (cm 2 /Vs)1450/ /1600 Saturation velocity (cm/s)0.8x10 7 2x10 7 Breakdown field (V/m)3x x10 7 Dielectric Constant Displacement energy (eV) e-h creation energy (eV)3.613 Av. e-h pairs per MIP per micron8936 Charge collection distance (micron)full~250 Low leakage current, shot noise Fast signal collection Low capacitance, noise Radiation hardness Smaller signal Thanks R. Wallny (UCLA)

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/  m Charge collection distance ~ 250 micron in poly-crystal diamonds, longer in single crystal. Thanks H. Kagan (Ohio State)

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)

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

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

Current Vendors Element Six (UK based, subsidiary of de Beers, S. Africa) ( 2.1x2.1 cm 2 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)

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 From Diamond to Detector Once this is done, we can think about reading the thing out with “standard” silicon electronics.

Lithography & Metallization Options 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. (including, wire bonding and making carrier boards) NSFL director Cyrus Shafai giving tour to UWinnipeg students Dec (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)

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

HALL-C Schematic 4 staggered Planes of 2.1x2.1 cm 2 CVD diamond crystals ~  m thick micron pitch. 2 planes + motion mechanism to be built by Winnipeg, U. Manitoba & TRIUMF 2 planes to be build by MSU

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

NSERC budget table

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

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.