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# Update from the Hall: Why is the MIP not distinct? - PowerPoint PPT Presentation

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?

Thomas K Hemmick

• 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:

• We do not have a shaper.

• We digitize (sample) waveformof the V(preamp) directly.

• “Post”-“Pre” = Charge.

• Centroid = Pulse Time

• RMS = Rise Time.

• Analysis presently does allthree of these.

• Minor trouble from previouspulses interfering…

• 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

• “Derivative” showsclear peak in slide 4.

• Centroid of peak quite tight for big pulses.

• RMS narrow for big pulses.

• 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.

• 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:

• 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.