Difference between revisions of "CDC prototype more on timing 3"

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|+Drift times for untracked, tracked and first hits in ch20 (first hit = earliest hit of all hits for that event)   
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|+Drift times for untracked, tracked and first hits in ch20 (first hit = earliest hit of all hits for that event)  Plotted in the hope of adding evidence to the theory that the peaks in the drift time
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histogram are caused by after-event ringing in the prototype.
 
|[[Image:run_31756_dt.png|thumb|x250px|track91 prototype horizontal, ame settings as previous set]]
 
|[[Image:run_31756_dt.png|thumb|x250px|track91 prototype horizontal, ame settings as previous set]]
 
|[[Image:run_31756_dtz.png|thumb|x250px|larger scale]]
 
|[[Image:run_31756_dtz.png|thumb|x250px|larger scale]]
 
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Revision as of 09:24, 29 March 2012

Latest approach to hit finding is as follows:

  1. Find a hit channel and filter events
    1. Calculate mean pedestal Pm & s.d. (σ) for first 100 samples in 100 events (trigger is approx sample 200)
    2. Set a threshold Pm + Tpm (Tpm ~ 3.5 σ) for further investigation, select events & channels where adc value exceeds this
  2. Calculate event pedestal
    1. Calculate event pedestal Pevt for current event & channel, as mean of 100 samples ending 10 samples before trigger time
  3. Use event pedestal to find high threshold time and new local pedestal
    1. Upsample data from samples 150 to 350 (max drift time + trigger time is approx sample 290)
    2. Select events where adc value goes over a high threshold Pevt + Tpe at point x (Tpe ~ 5sigma))
    3. Find a local pedestal Ploc as adc value at Np upsampled points (minisamples) before x (eg Np=15)
  4. Use local pedestal to find high and low threshold times
    1. Search forward from x-Np to find point x1 where data goes over a slightly less high threshold Ploc + Th where Th ~ 4 σ
    2. Search backward from x1 to find point x2 where data goes below low threshold Ploc + Tl where Tl ~ σ

To find where to take local pedestal:

Mean change in ADC value
Mean change in ADC value
Distribution of ADC values after subtracting pedestal at different Np
20 minisamples before threshold crossing
15 minisamples before threshold crossing
12 minisamples before threshold crossing
10 minisamples before threshold crossing
5 minisamples before threshold crossing
ADC values after subtracting pedestal at different Np
20 minisamples before threshold crossing
15 minisamples before threshold crossing
12 minisamples before threshold crossing
10 minisamples before threshold crossing
5 minisamples before threshold crossing
Resolution after subtracting pedestal at different Np for Th1 5sigma, Th = 4sigma, Tl = 1sigma
20 minisamples before threshold crossing (tz=8)
15 minisamples before threshold crossing (tz=7)
12 minisamples before threshold crossing (tz=6)
10 minisamples before threshold crossing (tz=6)
File:Run 31761 track86 np5.png
5 minisamples before threshold crossing (tz=6)

Optimised thresholds and Np - best combination for this data (2100V, 50/50 Ar/CO2, prototype tilted at 25o to horizontal) is Th1 5sigma, Th = 4sigma, Tl = 1sigma and Np = 13 or 14 with dt=6ns.

Drift-time=Tl crossing time; Th1 5sigma, Th = 4sigma, Tl = 1sigma, Np=14, dt=6
Resolution ch20
Resolution with drift distance ch20
Resolution with drift distance ch20
Resolution with drift distance ch20
Drift-time=Projection from Th through Tl to Ploc; Th1 5sigma, Th = 4sigma, Tl = 1sigma, Np=13, dt=6
Resolution ch20
Resolution with drift distance ch20
Resolution with drift distance ch20
Resolution with drift distance ch20
Drift-time=Intercept of straight line fit of crossing-points of Th Tl and their midpoint with Ploc; Th1 5sigma, Th = 4sigma, Tl = 1sigma, Np=13, dt=6
Resolution ch20
Resolution with drift distance ch20
Resolution with drift distance ch20
Resolution with drift distance ch20

RMS is least for Drift-time=Projection from Th through Tl to Ploc. Use this to look at data taken with prototype at different angles. All data above were with prototype at 25o to horizontal

Prototype horizontal Drift-time=Projection from Th through Tl to Ploc; Th1 5sigma, Th = 4sigma, Tl = 1sigma, Np=13, dt=6
Resolution ch20
Resolution with drift distance ch20
Resolution with drift distance ch20
Resolution with drift distance ch20
Prototype 25o to horizontal Drift-time=Projection from Th through Tl to Ploc; Th1 5sigma, Th = 4sigma, Tl = 1sigma, Np=13, dt=6
Resolution ch20
Resolution with drift distance ch20
Resolution with drift distance ch20
Resolution with drift distance ch20
Prototype 35o to horizontal Drift-time=Projection from Th through Tl to Ploc; Th1 5sigma, Th = 4sigma, Tl = 1sigma, Np=13, dt=6
Resolution ch20
Resolution with drift distance ch20
Resolution with drift distance ch20
Resolution with drift distance ch20


Prototype 45o to horizontal Drift-time=Projection from Th through Tl to Ploc; Th1 5sigma, Th = 4sigma, Tl = 1sigma, Np=13, dt=6
Resolution ch20
Resolution with drift distance ch20
Resolution with drift distance ch20
Resolution with drift distance ch20
Leading edge gradient from Th to Tl with Ploc; Th1 5sigma, Th = 4sigma, Tl = 1sigma, Np=13, dt=6
Prototype horizontal
Prototype 25o to horizontal
Prototype 35o to horizontal
Prototype 45o to horizontal
Drift times for untracked, tracked and first hits in ch20 (first hit = earliest hit of all hits for that event) Plotted in the hope of adding evidence to the theory that the peaks in the drift time histogram are caused by after-event ringing in the prototype.
track91 prototype horizontal, ame settings as previous set
larger scale
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