Resolutions

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Prelude

  • Two gases are used: 70/30 and 90/10 Ar/CO2
  • Two fADC clock settings are used: 125 and 200 MHz
  • Drift time spectra (DCOG method is used):
90/10 Ar/CO2 drift time spectra.
70/30 Ar/CO2 drift time spectra.
  • Red line is fit to get absolute minimal drift time
    • Best tracking results if extracted minimal drift time + 1 time sample
  • Samples per rising edge - 2 extra samples 125 -> 200 MHz
Samples/rising edge - 70/30 Ar/CO2 - 125~MHz clock.
Samples/rising edge - 70/30 Ar/CO2 - 200~MHz clock.
  • Time-2-distance relation:
    • GARFIELD is used. To get best resolutions out of it:
      • 68/32 Ar/CO2 is put in GARFIELD for 70/30 gas
      • 89/11 Ar/CO2 is put in GARFIELD for 90/10 gas
      • +-6% CO2 can give 100~ns difference


Resolutions

  • Difference in gases - blue line is a model prediction:
Resolutions (in um) as a function of distance to the wire (in mm) for 70/30.
Resolutions (in um) as a function of distance to the wire (in mm) for 90/10.
  • 90/10 worse because shorter drift times.
  • Model contains:
    • Timing resolution (0.75 length of time sample)
    • accuracy
    • diffusion (Garfield)


  • Table with resolutions for straw 7 and different clock settings:
    • high: with hit removed from tracking
    • low: with hit included
Distance from wire [mm] Resolution (low) [um] Resolution (high [um]
125 MHz 200 MHz 125 MHz 200 MHz
0-1 388 394 404 396
1-2 346 292 346 205
2-3 209 191 222 210
3-4 142 135 166 165
4-5 118 96 164 151
5-6 85 88 148 164
6-7 67 70 165 174
7-8 65 63 158 169


  • The difference between high and low is largest for 1-3 mm driftdistances but overall the difference is not that big.
  • Gas mixture has a big impact
  • We might not have a big enough lever arm:
Drawing of the end plate of the small prototype.


GARFIELD - DATA

Below 70/30 gas mixture ch 7: left MC, right data

Resolutions as a function of drift distance (MC).
Resolutions as a function of drift distance (data).

To do

  • There is a full simulation of the chamber and results are on there way
  • We are testing 80/20 gas right now
  • We want to test the same gas mixture as FDC uses
  • We also want to try and add ethane
  • Try different timing algorithms
  • Find a way to extract the timing resolution directly