Photosensors

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