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Photodetector Timing Resolution Burle Micro-Channel Plate Photo Multiplier Tubes (MCP-PMTs)

Photodetector Timing Resolution Burle Micro-Channel Plate Photo Multiplier Tubes (MCP-PMTs). H. Wells Wulsin SLAC Group B Winter 2005. Photo Multiplier Tube Specifications. End Station A Setup. Electronics: ADC Single threshold discriminator TDC (25 ps/cnt). Quartz bars. Pad 0. Pad 1.

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Photodetector Timing Resolution Burle Micro-Channel Plate Photo Multiplier Tubes (MCP-PMTs)

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  1. Photodetector Timing ResolutionBurle Micro-Channel Plate Photo Multiplier Tubes (MCP-PMTs) H. Wells Wulsin SLAC Group B Winter 2005

  2. Photo Multiplier Tube Specifications H.W. Wulsin

  3. End Station A Setup • Electronics: • ADC • Single threshold discriminator • TDC (25 ps/cnt) Quartz bars Pad 0 Pad 1 Path of test beam Pad 3 Pad 2 Mylar attenuators Burle MCP-PMT PiLas laser, 635 nm (int. trigger) H.W. Wulsin

  4. Limits to MCP Timing Resolution • Cross-talk between channels • Charge-sharing between pads • Electronics noise • Avalanche fluctuations [focus of this analysis] H.W. Wulsin

  5. Timing resolution varies with ADC • TDC measures hit time when pulse exceeds level set by single threshold discriminator. • Size of pulse (# photoelectrons) affects the measured hit time. • More photoelectrons reduce the variability of measured hit time (avalanche fluctuations have a smaller effect). Single photoelectron pulses (2 mV/div) ~300 photoelectrons / pulse (200 mV/div) Threshold Threshold 1 ns 1 ns H.W. Wulsin

  6. ADC Distribution of Runs 1-8, taken 11-22-04, 11-24-04 Entries ADC (counts) H.W. Wulsin

  7. TDC v. ADC, Runs 1-8 TDC TDC (counts) ADC ADC (counts) H.W. Wulsin

  8. TDC Histogram, Runs 1-8 entries TDC (counts) H.W. Wulsin

  9. Linear fit to Run 8 TDC = -0.0209(ADC) + 640.1 TDC (counts) ADC (counts) H.W. Wulsin

  10. Linear correction to Run 8 TDC TDC ADC ADC σcorr = 30.0 ps entries entries σraw = 31.0 ps H.W. Wulsin TDC TDC

  11. Linear fit to Run 7 TDC = -0.098(ADC) + 671.5 TDC (counts) ADC (counts) H.W. Wulsin

  12. Linear correction to Run 7 TDC TDC ADC ADC σcorr = 48.5 ps entries entries σraw = 53.5 ps H.W. Wulsin TDC TDC

  13. Hyperbolic fit to Runs 1-6 TDC = 632.6 + 509.8 / (ADC – 258.6) TDC (counts) ADC (counts) H.W. Wulsin

  14. Hyperbolic correction to Runs 1-6 TDC TDC ADC ADC σcorr = 320 ps σraw = 470 ps entries entries TDC TDC H.W. Wulsin

  15. Independent fits to three data sets H.W. Wulsin

  16. Optimized total fit TDC (counts) ADC (counts) By Hand: TDC = 619 + 165/√(ADC – 262) By Recursion: TDC = 619.2 + 160.7/√(ADC – 262.2) H.W. Wulsin

  17. Total correction for Runs 1-8 TDC TDC ADC ADC TDC TDC H.W. Wulsin ADC ADC

  18. Timing Resolution Correction: All Runs entries entries TDC (counts) TDC (counts) FWHM ~ 50 counts ADC FWHM ~ 15 counts ADC H.W. Wulsin

  19. Use Run 1 (maximum attenuation): ADC counts  photoelectrons entries No TDC Signal TDC Signal Recorded No TDC Signal entries entries TDC Signal Recorded entries entries ADC (counts) ADC - Pedestal (counts) ADC (counts) Pedestal value: 265.4 counts ADC Single photoelectron mean ADC: 2.1 counts 1 photoelectron = 2.1 counts ADC H.W. Wulsin

  20. Timing Resolution vs. Photoelectrons σ (ps) σ (ps) Npe Npe σ = 9.08 + 214.61 / √(Npe – 0.45) H.W. Wulsin

  21. Comparison to Previous Analysis Wells Josef (different data runs) photoelectrons photoelectrons Similar resolution spectrum H.W. Wulsin

  22. Conclusions • Achieved timing resolution of 30 – 50 ps for ~100 photoelectrons (Run 8) down to ~30 photoelectrons (Run 7). • Correction for timing – photon correlation most helpful in comparing disparate runs. • For constant number of photoelectrons, correction less useful. • Further study: • Confirm # photoelectrons per ADC count. • Examine charge-sharing between pads. H.W. Wulsin

  23. Thank you to all of Group B for your help all quarter! Thanks to all Group B for lots of help this quarter! H.W. Wulsin

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