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Gain measurement with LED and time-over-threshold

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

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Gain measurement with LED and time-over-threshold

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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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