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Photosensors

Photosensors. Kevin McFarland University of Rochester MINER n A meeting, June 2003. Why photosensors?. Our current task is to understand the target region of the detector segmented scintillator strips with WLS fiber readout. Cheap target material! side and rear detectors are likely similar

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Photosensors

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  1. Photosensors Kevin McFarland University of Rochester MINERnA meeting, June 2003

  2. Why photosensors? • Our current task is to understand the target region of the detector • segmented scintillator strips with WLS fiber readout. Cheap target material! • side and rear detectors are likely similar • Our detector costs are likely dominated by photosensors and electronics! Kevin McFarland, Photosensors

  3. Ground Rules • Cost 20,000 channels • fibers of either 0.5mm or 1.2mm diameter • no guidance offered re: multiplexing! yet! • Consider technical risks and limitations posed by sensors • Costs from WLS fiber through electronics Kevin McFarland, Photosensors

  4. More Ground Rules… • Things we know about beam and “detector” • 10 microsecond spill. ~0.5Hz rep. rate • MIP light from MINOS scintillator extrusions (4x1cm2) • 50 photons at ~510nm after 4m WLS fiber • 100 photons after 1m WLS fiber • require high dynamic range • MIP to proton range out Kevin McFarland, Photosensors

  5. Final Ground Rules… • This is the time to be critical of assumptions, ask questions, etc. • We need to make a decision within 4-6 weeks of which technologies we continue to bring to proposal stage! • Even if you don’t plan to build it, you may need to analyze it! • Your presenters are prepared for this abuse! Kevin McFarland, Photosensors

  6. Our Dedicated Crew… • II/CCD: Steve Manly, Ron Ransome • APD (Avalanche Photodiodes): Howard Budd • MAPMT: yours truly • Two sided readout issues: Arie Bodek • different technologies on each side? • Thank you!!! Kevin McFarland, Photosensors

  7. MAPMTs • Our initial bias… • this is a “safe” but expensive technology • certainly a well-worn path, e.g., MINOS • timing to few ns level OK • possible to resolve multiple hits outside ~30ns window? but electronics $$$$ • dynamic range limited by electronics • multiplexing onto face of sensor can be done for “free” (pixel size > fiber size) Kevin McFarland, Photosensors

  8. Hamamatsu R5900-00-M64 • Used for the MINOS near detector • Operated with 106 gain • Gain can vary by factor of 2 to 3 from device to device • Pixel size 2x2 mm2, 64 channels • % level crosstalk • Cost in quantity for MINOS was $20/ch • In context of off-axis proposal, $11-$14/ch is current estimate Kevin McFarland, Photosensors

  9. MINOS M64 Studies (Oxford) • Gain variations for a batch of M64 PMTs • set to 106 gain • Not a problem; just a matter of batch testing. Kevin McFarland, Photosensors

  10. Conventional Blue Y11 3 HF MINOS M64 Studies • QE~13% for blue-green WLS light (Y11 fiber) Clear fiber attenuation vs l QE (%) of ensemble of M64s Kevin McFarland, Photosensors

  11. MINOS M64 Studies • Dark count rate at 1/3 p.e. threshold • Noise rate for multi-pe signal is very low Kevin McFarland, Photosensors

  12. MINOS M64 Studies • Gain versus pixel for a typical M64 • Relative gain believed to be stable over time Kevin McFarland, Photosensors

  13. Technical Risks of MAPMTs • Are there any? • Fringe fields from near detector? • my conclusion: solvable. $ for shields • will need to monitor changes in field? • Gain drift? • low through-going muon rate in detector may require frequent external calibration methods • totally solvable. Flasher system… • sourcing may also be required to study long term scintillator and fiber degradation Kevin McFarland, Photosensors

  14. Readout Costs • An excellent assumption is that costs are dominated by the front end • MINOS far detector is 23K channels after multiplexing • scaling their front-end M&S+SWF TDR costs, get $0.7M/20K PMT pixels. (If I did this right…) • MINOS ~ doubles this cost with other readout and DAQ components. (No evaluation of sanity of this!) • I haven’t done enough work here… Kevin McFarland, Photosensors

  15. Cost Summary • Different MUX strategies for 20K bars • 1.2mm fiber limits optical MUX to 2x Kevin McFarland, Photosensors

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