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Update from the Hall: Why is the MIP not distinct?

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Update from the Hall: Why is the MIP not distinct?. Thomas K Hemmick. Classical Signal Conditioning. Charge-Sensitive pre-amp Charge collected increases like an ascending staircase. V=Q/C with RC decay applied. Derivative of V(pre) shows spikes at each charge injection.

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classical signal conditioning
Classical Signal Conditioning
  • Charge-Sensitive pre-amp
    • Charge collected increaseslike an ascending staircase.
    • V=Q/C with RC decay applied.
    • Derivative of V(pre) showsspikes at each charge injection.
    • Shaper uses time-weightingfunction to produce pulse.
  • Mathematically:
waveform analysis
WaveForm Analysis
  • We do not have a shaper.
  • We digitize (sample) waveformof the V(preamp) directly.
  • Simple Access to things you want to know:
    • “Post”-“Pre” = Charge.
    • Centroid = Pulse Time
    • RMS = Rise Time.
  • Analysis presently does allthree of these.
  • Minor trouble from previouspulses interfering…
previous pulses
Previous Pulses
  • Probability:
    • 200 kHz of BBC LL1.
    • 400 kHz of interactions.
    • 10 MHz of crossings
    • 4% chance of collision.
  • Latency:
    • Pre-amp crosses zero at 2 msec.
    • Pre-amp crosses after 20 crossings.
    • Probability of a prior event:
    • These MOSTLY have decayed away but not all.
  • For now cut away when Sample[0]!=0

Pulses from prior

Crossings clearly visible

Decay of pulse duringdigitization interval

can be significant

samples of pulse analysis
Samples of Pulse Analysis
  • “Derivative” showsclear peak in slide 4.
  • Centroid of peak quite tight for big pulses.
  • RMS narrow for big pulses.
what do you call signal
What do you call signal?
  • Sample[i] is a plot of charge vs. time.
  • S[i+n]-S[i] is a plot of current vs time.
  • I believe that CHARGE is our signal.
  • Note some simple math:
  • If you integrate back overthe differences, you eliminatesamples in the middle.
  • Is the signal current:
    • MAX(Di) as a single sample.
    • Amplitude to fit (e.g. Gauss)to get peak current?
  • Or is the signal charge:
    • Post – Pre.
summary of progress
Summary of Progress:
  • We see a large difference in yield of big pulses with a difference in the grid bias.
  • The yield in forward bias SHOULD be MIPs.
  • No efforts have yet resulted in a narrow MIP peak:
    • Single pad same as “allpads”.
    • Sorted into columns same.
    • Increased drift field same.
    • Oscilloscope spectrum same.
  • Confusion reigns supreme…
    • Will having a tag of which pad to lookat help?
    • If MIP is not distinct, why should blobbe tight distribution.
    • Why was (is?) 55Fe a tight peak?
  • Optimist:
    • Please someone tell me how to be optimistic.