Notes from July 22nd, 2008 Meeting

Use Leo's book about PMT's and CMT's.

Leading Edge Discriminator

Correcting time walk method

• send pulse into ADC
  • analog to digital converter
  • measures size of pulse

• Constant Fraction Discriminator
  • Finds peak
  • For each pulse, sets threshold at .2 V of peak.
  • Here, the threshold tells us when to fire. If the threshold is small, it'll trigger on noise.

We need to try to change the width. Why does the width matter? Suppose we made the width too small. Then, we'll get multiple pulses because it'll count all the places the value is greater than the threshold which isn't what we want. We want our width to be the size of where the analog signal will hit the threshold both times.