Difference between revisions of "CDC prototype more on timing 3"
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|[[Image:run_31761_track86_np10.png|thumb|x250px|10 minisamples before threshold crossing (tz=6)]] | |[[Image:run_31761_track86_np10.png|thumb|x250px|10 minisamples before threshold crossing (tz=6)]] | ||
|[[Image:run_31761_track86_np5.png|thumb|x250px|5 minisamples before threshold crossing (tz=6)]] | |[[Image:run_31761_track86_np5.png|thumb|x250px|5 minisamples before threshold crossing (tz=6)]] | ||
+ | |} | ||
+ | |||
+ | Optimised thresholds and N<sub>p</sub>, best combination for this data is T<sub>h1</sub> 5sigma, T<sub>h</sub> = 4sigma, T<sub>l</sub> = 1sigma and N<sub>p</sub> = 13 or 14 with dt=6ns. | ||
+ | {| border="0" cellpadding="2" | ||
+ | |+Drift-time=T<sub>l</sub> crossing time; T<sub>h1</sub> 5sigma, T<sub>h</sub> = 4sigma, T<sub>l</sub> = 1sigma, N<sub>p</sub>=14, dt=6 | ||
+ | |[[Image:run_31761_track86_np14_res20.png|thumb|y250px|Resolution ch20]] | ||
+ | |[[Image:run_31761_track86_np14_resdist20.png|thumb|y250px|Resolution with drift distance ch20]] | ||
+ | |[[Image:run_31761_track86_np14_xchunks.png|thumb|y250px|Resolution with drift distance ch20]] | ||
+ | |[[Image:run_31761_track86_np14_xchunks3.png|thumb|y250px|Resolution with drift distance ch20]] | ||
|} | |} |
Revision as of 10:15, 28 March 2012
Latest approach to hit finding is as follows:
- Find a hit channel and filter events
- Calculate mean pedestal Pm & s.d. (σ) for first 100 samples in 100 events (trigger is approx sample 200)
- Set a threshold Pm + Tpm (Tpm ~ 3.5 σ) for further investigation, select events & channels where adc value exceeds this
- Calculate event pedestal
- Calculate event pedestal Pevt for current event & channel, as mean of 100 samples ending 10 samples before trigger time
- 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)
- Select events where adc value goes over a high threshold Pevt + Tpe at point x (Tpe ~ 5sigma))
- Find a local pedestal Ploc as adc value at Np upsampled points (minisamples) before x (eg Np=15)
- Use local pedestal to find high and low threshold times
- Search forward from x-Np to find point x1 where data goes over a slightly less high threshold Ploc + Th where Th ~ 4 σ
- 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:
Optimised thresholds and Np, best combination for this data is Th1 5sigma, Th = 4sigma, Tl = 1sigma and Np = 13 or 14 with dt=6ns.