Microscope Performance

1. GlueX collaboration meeting, Newport News, Feb. 2-4, 2011 Microscope Performance at elevated dark rates Richard Jones University of Connecticut

2. Outline • the microscope readout • effects of neutron radiation • Monte Carlo model • simulation of a pulse train • time resolution • detection efficiency • results vs. dark rate • lifetime projections GlueX collaboration meeting, Newport News, Feb. 2-4, 2011

3. rates at 2.2 mA on a 10-4 radiator (108g/s) the microscope readout Design requirements • spectrum coverage 70% - 75% in 0.1% steps • energy resolution 0.5% (60 MeV) r.m.s. • rate capability 500 MHz per GeV • tagging ratio optimum goal 70% GlueX collaboration meeting, Newport News, Feb. 2-4, 2011

4. the microscope readout Design parameters • square scintillating fibers • size 2 x 2 x 20 mm3 • clear light guide fibers • alignedalong electron directionfor reduced background sensitivity • readout withsilicon photomultipliers(SiPMs) SiPM sensors clear light fibers scintillating fibers focal plane electron trajectory GlueX collaboration meeting, Newport News, Feb. 2-4, 2011

5. effects of neutron radiation • Neutron rates estimated using tagger hall simulation [1]. • Experiments show the main effect of radiation damage on SiPM’s is to increase the dark rate [2,3]. in the region of the microscope readout without shielding 180 mrem/h with shielding 30 mrem/h units chosen to assess Si device effects when operating the beam at full intensity of 108 g/s on the GlueX target [1] A. Somov, “Neutron Background Estimates in the Tagger Hall”, gluex-doc-1646, 2010. [2] Y. Qiang, “SiPM Radiation Hardness Test”, report available at http://www.jlab.org/Hall-D/software/wiki/index.php/SiPM Radiation Hardness Test [3] Y. Musienko, D. Renker, Z. Charifoulline, K. Deiters, S. Reucroft, and J. Swain, “Study of Radiation Damage Induced by 82 MeV Protons on Multi-pixel Geiger-Mode Avalanche Photodiodes”, Nucl. Instr. Meth. A610 (2009) 87-92. GlueX collaboration meeting, Newport News, Feb. 2-4, 2011

6. effects of neutron radiation Measurements made at Jlab in Hall A • Hamamatsu 3mm MPPC • rise is roughly linear • remains after recovery period • slope is factor 8 / 100 rem • some evidence that the slope is decreasing with dose initial dark rate: 6 MHz final dark rate: 72 MHz total dose after 33 h = 153 rem [2] Y. Qiang, “SiPM Radiation Hardness Test”, report available at http://www.jlab.org/Hall-D/software/wiki/index.php/SiPM Radiation Hardness Test GlueX collaboration meeting, Newport News, Feb. 2-4, 2011

7. effects of neutron radiation Measurements with 82 MeV protons at PSI • use Hall A conversion factor • total dose: 830 rem • expected DR increase: x 67 • observed DR increase: x 33 • results are consistent if one allows for nonlinear increase 1 rem → 2.4 × 107 neq/cm2 2x1010/cm2 of 1 MeV neutron-equivalent flux [3] Y. Musienko, D. Renker, Z. Charifoulline, K. Deiters, S. Reucroft, and J. Swain, “Study of Radiation Damage Induced by 82 MeV Protons on Multi-pixel Geiger-Mode Avalanche Photodiodes”, Nucl. Instr. Meth. A610 (2009) 87-92. GlueX collaboration meeting, Newport News, Feb. 2-4, 2011

8. effects of neutron radiation Measurements with 82 MeV protons at PSI [3] Y. Musienko, D. Renker, Z. Charifoulline, K. Deiters, S. Reucroft, and J. Swain, “Study of Radiation Damage Induced by 82 MeV Protons on Multi-pixel Geiger-Mode Avalanche Photodiodes”, Nucl. Instr. Meth. A610 (2009) 87-92. GlueX collaboration meeting, Newport News, Feb. 2-4, 2011

9. tagger hall projections • 10 year lifetime of readout electronics • 107 seconds of beam per year • always running at full intensity • projected dark rate increase total beam time: 28,000 h neutron dose: 5,000 rem (unshielded) 900 rem (shielded) linear from [2]: 400 (unshielded) linear from [3]: 200 (unshielded) 35 (shielded) GlueX collaboration meeting, Newport News, Feb. 2-4, 2011

10. Monte Carlo model of a SiPM single pixel behavior: • gain = Cpixel(Vb-VBD) • recovery is exponential • recovery time constant • “recovery time” = 3tr =time for pixel to reach 95% of full gain V Vb gain VBD t tr tr = Rquench (Cpixel+Cquench) GlueX collaboration meeting, Newport News, Feb. 2-4, 2011

11. Monte Carlo model of a SiPM expected pulse height distribution energy deposition in scintillator number of pixels @ 15% PDE GlueX collaboration meeting, Newport News, Feb. 2-4, 2011

12. simulation questions • Can the performance goals be achieved with SiPM readout, under initial dark rate conditions? • What is the performance like at elevated dark rate? parameter design goal single-channel pulse rate 4 MHz electron detection efficiency 95 % electron hit time resolution 200 ps Hint: there is a scale set for dark rate by the rate x <pulse height> 109 Hz GlueX collaboration meeting, Newport News, Feb. 2-4, 2011

13. simulation of a single pulse • pulse model includes SiPM, preamp, and 40’ cable • pulse shape was validated in bench tests with 2x2 CPTA device • points are from model, curve is an empirical fit to the points GlueX collaboration meeting, Newport News, Feb. 2-4, 2011

14. simulation of a pulse train • pulse train simulated by summing pulses from individual pixels • includes scintillator decay time, pixel recovery, cross-talk, … Hamamatsu S10931-25P MPPC at 4 MHz signal and 10 GHz dark rate after-pulses GlueX collaboration meeting, Newport News, Feb. 2-4, 2011

15. pulse height distributions • first results: signal pulse heights at 4 MHz and 107 Hz dark rate • news: the CPTA (Photonique) device is saturating (tr = 1 ms) • Hamamatsu device is ok (tr = 15 ns) – hence the after-pulsing ! Hamamatsu 3x3mm2 MPPC CPTA 2x2mm2 SSPM GlueX collaboration meeting, Newport News, Feb. 2-4, 2011

16. pulse height distributions • first results: signal pulse heights at 4 MHz and 107 Hz dark rate • news: the CPTA (Photonique) device is saturating (tr = 1 ms) • Hamamatsu device is ok (tr = 15 ns) – hence the after-pulsing ! Hamamatsu 3x3mm2 MPPC CPTA 2x2mm2 SSPM GlueX collaboration meeting, Newport News, Feb. 2-4, 2011

17. time resolution study • Hamamatsu device at 4 MHz signal, 10 MHz dark rate time walk correction time resolution (RMS) GlueX collaboration meeting, Newport News, Feb. 2-4, 2011

18. time resolution study • Hamamatsu device at 4 MHz signal, elevated dark rates • effects in time resolution start to become noticeable at 1010 Hz dark rate 100 GHz dark rate 10 GHz GlueX collaboration meeting, Newport News, Feb. 2-4, 2011

19. efficiency study • Hamamatsu device at 4 MHz signal, elevated dark rates • effects in efficiency start to become noticeable at 1010 Hz dark rate 100 GHz dark rate 10 GHz GlueX collaboration meeting, Newport News, Feb. 2-4, 2011

20. conclusions • CPTA (Photonique) device is ruled out based on insufficient high-rate capability (slow pixel recovery) • Hamamatsu 3x3mm device (14,400 pixels) meets all of the requirements for the microscope readout. • Estimates for dark rate in a microscope readout based on the MPPC S10931-025P are in the range 0.8 – 1.6 GHz after 10 years of expected operation. • Simulation has shown that the Hamamatsu MPPC can satisfy all performance requirements up to dark rates of 10 GHz, which gives a healthy safety factor. GlueX collaboration meeting, Newport News, Feb. 2-4, 2011

21. GlueX collaboration meeting, Newport News, Feb. 2-4, 2011