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Compton Electrons Dipangkar Dutta & Jeff Martin Mississippi State & University of Winnipeg.

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Presentation on theme: "Compton Electrons Dipangkar Dutta & Jeff Martin Mississippi State & University of Winnipeg."— Presentation transcript:

1 Compton Electrons Dipangkar Dutta & Jeff Martin Mississippi State & University of Winnipeg

2 Struck electron loses energy equivalent to photon energy increase. Very little angular deflection. At 850 MeV, max energy loss is E  = 25 MeV [Bates]. Struck electron is momentum analyzed using downstream dipole magnet. Compton Recoil Electron Kinematics e.g. Mainz Compton

3 Compton Survey (focusing on electron detection) LocationBeam energyPhoton Det.Electron Det. Hall A1.0 – 6.0 GeVPbWO 4 silicon Mainz0.1 – 0.9 GeVNaISciFi SLAC45.6 GeVW / quartzPb / gas Č HERA Long.27.5 GeVNaBi(WO 4 )none Bates0.3 – 1.0 GeVCsInone others: NIKHEF, VEPP-3, VEPP-4, SPEAR, CESR, DORIS, PETRA, HERA trans., LEP

4 Typical Requirements for Electron Detector (Mainz & Hall A) ~ 0.5 mm spatial resolution in dispersive direction high efficiency (no gaps) high rate capability (up to 100 kHz) rad hard Notes: Both Mainz & Hall A use CW laser operation (we don’t intend to) background rates highly dependent on energy and beam tune [Nanda, Hall A]

5 Rates Hall-A: Signal rate : 5KHz for 8  A current @ 500W (energy independent) Background : @ 2GeV is 2KHz (depends on beam tune) Hall-C: Laser power is ave. 90W with duty factor of 0.15% Signal rate: 15-20KHz at 180  A Background: low (scaled from Hall A rates) - Thanks S. Nanda - Thanks Dave Multiplicity: ~1.5 per pulse

6 Technologies Under Consideration for Hall C Compton Silicon –advantages: proven technology (Hall A), acceptance easy to understand, rad hard. –disadvantages: slow? potentially high electronics costs. SciFi –advantages: fast, cheap, use Si-PM readout –disadvantages: rad hardness? more difficult acceptance? –alternate: quartz fiber; same readout, very rad hard. GEM –advantages: cheap, rad hard, fairly fast. –disadvantages: electronics costs hard to estimate, potentially complicated R&D project on its own.

7 Si cost estimate (C. Davis, et al 2005 NSERC submission) ItemCost (kCAD) Si detectors (8 x PIPS-S-8)44 Electronics @ 192 channels82 Cooling8 Misc2 Travel10 Total146 Note: RTI category 1 limit is $150 kCAD.

8 Options for Fiber Based Recoil Electron Detector  Scintillating Fiber Based Device (SciFi, e.g. Mainz Compton)  Quartz Fiber Based Device (e.g. SLAC Compton -photon detector, 25  resolution)

9 SciFi Based Electron Detector SciFi available from 3 manufacturers Bicron, Kuraray & Pol.Hi.Tech. Typical light yield 4.5 p.e./mm, for 1mm diameter fiber. Achieved resolutions of ~125  m. Kararay is the most radiation hard no damage detected when exposed to 1Mrad (tested with e - beams). E. C. Aschenauer et al. hep-ex/9710001 “We have not found any noticeable change in the detector properties over time.” -Yoshio Imai (Mainz Compton)

10 Quartz Fiber Based Detector Signal through Cerenkov radiation, thus low photon yield (only few% of photons is trapped) ~1 pe/GeV/cm. Also incidence angle dependent. But 25  m resolution achieved at SLAC, extremely radiation hard ~ 2 Grad, insensitive to soft synchrotron radiation and high linearity.

11 Light Detection SiPM: the new kid on the block Silicon Photo Multipliers - densely packed array of Avalanche Photo Diodes (~1000 in a 1mmx1mm grid) operating in Geiger mode (i.e. individual photo-electrons from each micro pixel cannot be distinguished). ~ 1 mm 20~100  m Depletion region ~ 2  m ~ 8  m Substrate 400 pixels First developed and produced by CPTA Russia. Now also Hamamatsu Photonics Mainz used Multi Anode PMTs made by Hamamatsu

12 PMTSiPM Gain~10 6 10 5 ~10 6 Photon Detection Efficiency 0.1 ~ 0.20.1~ 0.4 Responsefast Photon countingYesGreat Bias voltage~ 1000 V30 ~ 70 V SizeSmallCompact B fieldSensitiveNo influence CostNot lowLow (~$10) Dynamic rangeGoodNot so good StabilityGoodUnknown, maybe good Noise (fake signal by thermions) QuietNoisy (order of MHz) can reduce by cooling Performance

13 Roadmap to First Light 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


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