Difference between revisions of "CDC prototype more on timing 3"
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## Set a threshold T<sub>p</sub> (eg 3.5 σ) for further investigation, eg P<sub>m</sub> + T<sub>p</sub> , select events & channels where adc value exceeds this | ## Set a threshold T<sub>p</sub> (eg 3.5 σ) for further investigation, eg P<sub>m</sub> + T<sub>p</sub> , select events & channels where adc value exceeds this | ||
## Calculate event pedestal P<sub>evt</sub> as mean of samples 90 to 190 in current event | ## Calculate event pedestal P<sub>evt</sub> as mean of samples 90 to 190 in current event | ||
− | ## Select events where adc value goes over high threshold T<sub>h1</sub> + P<sub>evt</sub> (T<sub>h1</sub> ~ 5sigma) | + | ## (Maybe: Select events where adc value goes over high threshold T<sub>h1</sub> + P<sub>evt</sub> (T<sub>h1</sub> ~ 5sigma)) |
# Use event pedestal to find high threshold time and new local pedestal | # Use event pedestal to find high threshold time and new local pedestal | ||
## Upsample data from samples 150 to 350 (max drift time + trigger time is approx sample 290) | ## Upsample data from samples 150 to 350 (max drift time + trigger time is approx sample 290) | ||
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{| border="0" cellpadding="2" | {| border="0" cellpadding="2" | ||
− | |+Resolution after subtracting pedestal at different N<sub>p</sub> | + | |+Resolution after subtracting pedestal at different N<sub>p</sub> for T<sub>h1</sub> unused, T<sub>h2</sub> = 4sigma, T<sub>h1</sub> = 1sigma |
|[[Image:run_31761_track81c_np20.png|thumb|x250px|20 minisamples before threshold crossing]] | |[[Image:run_31761_track81c_np20.png|thumb|x250px|20 minisamples before threshold crossing]] | ||
|[[Image:run_31761_track81c_np15.png|thumb|x250px|15 minisamples before threshold crossing]] | |[[Image:run_31761_track81c_np15.png|thumb|x250px|15 minisamples before threshold crossing]] |
Revision as of 16:01, 22 March 2012
Latest approach to hit finding is as follows:
- Find a hit channel and event pedestal
- Calculate mean pedestal Pm & s.d. (σ) for first 100 samples in 100 events (trigger is approx sample 200)
- Set a threshold Tp (eg 3.5 σ) for further investigation, eg Pm + Tp , select events & channels where adc value exceeds this
- Calculate event pedestal Pevt as mean of samples 90 to 190 in current event
- (Maybe: Select events where adc value goes over high threshold Th1 + Pevt (Th1 ~ 5sigma))
- Use event pedestal to find high threshold time and new local pedestal
- Upsample data from samples 150 to 350 (max drift time + trigger time is approx sample 290)
- Search forward to find point x1 where data goes above a not quite so high threshold Th2 + Pevt where Th2 ~ 4 σ
- Find a local pedestal Ploc as adc value at Np upsampled points (minisamples) before x1 (eg Np=15)
- Use local pedestal to find low threshold time
- Search backward from x1 to find point x2 where data goes below low threshold Tl + Ploc where Tl ~ σ
To find where to take local pedestal: