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Gain Measurement of LED with Time-Over-Threshold ADC Using Passive Splitter and Thresholds

This study explores gain measurement techniques utilizing an LED driver and time-over-threshold (ToT) ADC in conjunction with a passive splitter. By modulating the charge (both voltage and time-width) to the LED, we can achieve significant variations in signal amplitude, demonstrating that small changes in charge yield large differences in emitted light. We'll analyze the ToT versus charge (Q) calibration curve for different threshold settings, comparing results to optimize gain measurements across multiple crystals. We also address challenges in sourcing LEDs with similar luminosity for accurate comparisons.

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Gain Measurement of LED with Time-Over-Threshold ADC Using Passive Splitter and Thresholds

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  1. Gain measurement with LED and time-over-threshold ADC passive splitter Analog out Threshold L Threshold H TDC LED LED driver LVDS out

  2. It is possible to span different regions of signal amplitude by modulating the charge (voltage and time-width) to the LED (with the CAMAC LED driver) A small variation in the charge injected into the LED produces a large difference in the produced light (and thus in the signal amplitude) The intrinsic fluctuation due to the LED alone is very small, compared to the s of the signal due to the gain of the PMT

  3. Original divider

  4. Modified divider • Reconstruct ToT vs. Q calibration curve using Q from ADC vs. ToT from TDC

  5. Compare two different thresholds: - As expected, higher threshold results in steeper curve

  6. Charge from ADC Charge from TDC Charge from ADC given a TDC hit

  7. Fit gain using Q from ADC • Using ToT vs. Q calibration curve reconstruct Q from ToT • Fit gain with usual method

  8. We have seen that is possible to use ToT vs. Q calibration curve to reproduce the gain measurement, for a single crystal • Now we want to: • Produce calibration curve for 1 crystal • Use this curve for several other crystals • Try to reproduce gain with ToT • Setup ready for 6 lead-glasses

  9. Small problem: find LED’s with similar luminosity • (in order to span similar charge/ToT regions)

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