1. Tagger Electronics Part 1: tagger focal plane microscope Part 2: tagger fixed array Part 3: trigger and digitization Richard Jones, University of Connecticut GlueX Electronics Meeting Apr. 6-7, 2006, Bloomington

2. Richard Jones, GlueX Electronics Meeting, Bloomington, April 6-7, 2006 2 photon beam exits from tagger inside vacuum, continues 70 m down to collimator cave and Hall D 1 mm Alhodoscope exit window is 1 mm Al 1 cm Alother walls of vacuum chamber are 1 cm Al 5 mm Alexposed side of electron exit channel is 5 mm Al Tagger focal plane broad-band focal plane hodoscope 144 readout channels short scint. rods max rate/chan: 2x10 6 (10 7 ) focal plane microscope 120 readout channels 600 scint. fibers max rate/chan: 2x10 5 (10 6 )

3. Richard Jones, GlueX Electronics Meeting, Bloomington, April 6-7, 2006 3 Microscope scintillating fiber design focal plane electron trajectory SiPM sensors scintillating fibers clear light fibers Design parameters Design parameters  square scintillating fibers  size 2 mm x 2 mm x 20 mm  clear light guide readout along electron direction  aligned along electron direction for reduced background sensitivity silicon photomultipliers SiPM devices  readout with silicon photomultipliers (SiPM devices)

4. Richard Jones, GlueX Electronics Meeting, Bloomington, April 6-7, 2006 4 Why 2D segmentation?   y 9 GeV 3 GeV collimator y y  This photon cannot get through the collimator but its electron still reaches the focal plane and produces a count there.  By reducing the acceptance of the tagging counters to a region part of the tagging efficiency lost through collimation is recovered. |  y | <  half-collimator (P  kick from crystal is negligible)

5. Richard Jones, GlueX Electronics Meeting, Bloomington, April 6-7, 2006 5 Silicon photomultiplier fiber readout  Excellent characteristics for this application: Fast timing (x2 faster than PMT’s) Dynamic range factor 1000-10000 Gain similar to phototube (10 6 ) Requires no HV (only ~50V bias) QE similar to PMT (higher in green, lower in blue)  Data reported by G. Lolos et.al.  Device  QE  550 nm SiPM 0.3 60% 20% PMT 1.0 5% 5% 437 nm SiPM 0.3 45% 15% PMT 1.0 25% 25%

6. Richard Jones, GlueX Electronics Meeting, Bloomington, April 6-7, 2006 6 Microscope requirements: channel count energy resolution 1.channel width from energy resolution: rate limitations: 2.channel width from rate limitations: margins: 3.additional margins: 4 MeV = 4 MeV 2 MHz 500 MHz/GeV 9 MeV 2 MHz is the rate seen by the central fiber for the case of transverse segmentation 30% margins 100 energy channels

7. Richard Jones, GlueX Electronics Meeting, Bloomington, April 6-7, 2006 7 Silicon photomultiplier fiber readout  Expected light yield for axial electrons: per energy channel  One complete electronics chain per energy channel  Individual SiPM bias voltage  Individual SiPM bias voltage setting under computer control  Conventional tagging is remotely selectable by enabling all rows  Tagger Review Panel (1/2006):  total path length in scintillator: 2 cm  scintillation light emitted: 10 4 photons / MeV  fiber capture fraction: 5%  quantum efficiency: 15%  SiPM coupling fraction: 20% 60 p.e. A few channels should have readout on all 5 fibers to enable monitoring of the stability of alignment.

8. Richard Jones, GlueX Electronics Meeting, Bloomington, April 6-7, 2006 8 Microscope electronics SiPM “bases”  SiPM “bases”  Programmable constant fraction discriminators: 120 channels  High resolution tdc (F1TDC): 120 channels  Pulse height needed:  Pulse height needed: FADC is a good choice: 120 channels  essential for setup  useful for monitoring performance  rates alone give incomplete information  Scalers counting on all channels: 120 channels bias voltage regulation  provides bias voltage regulation:  regulation range: 48 ± 8 V  regulation stability: 0.1 V  regulation control: 0.1 V steps  reasonable packing density: 600 channels on 20x10 3 cm 2

9. Richard Jones, GlueX Electronics Meeting, Bloomington, April 6-7, 2006 9 Fixed array electronics  Conventional 1” phototubes, bases  High voltage for phototubes: 144 channels  Timing needed:  Timing needed: High resolution tdc (F1TDC): 144 channels  for measuring coherent bremsstrahlung spectrum  time is compared with pair spectrometer trigger can run concurrently with experiment  at low intensities (10 7 ) can run concurrently with experiment only for special low-intensity runs  at high intensities (10 8 ) only for special low-intensity runs  Pulse height needed:  Pulse height needed: FADC may not be a good choice: 144 channels  essential for setup  at high intensities, monitor spectrum in integrating mode  Scalers counting on all channels: 144 channels

10. Richard Jones, GlueX Electronics Meeting, Bloomington, April 6-7, 2006 10 Channel count updates discussion…

11. Richard Jones, GlueX Electronics Meeting, Bloomington, April 6-7, 2006 11 Tagger trigger electronics TaggerOR TaggerOR fast logical OR of 120 channels from the microscope sent over fiber to GlueX trigger electronics Digitization of tagger signals Digitization of tagger signals probably located in the tagger area requires delivery of the GlueX clock and trigger to tagger area