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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Update from the hall why is the mip not distinct

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

Thomas K Hemmick


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.


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