Difference between revisions of "CDC prototype more on timing 3"
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# Find a hit channel and filter events | # Find a hit channel and filter events | ||
## Calculate mean pedestal P<sub>m</sub> & s.d. (σ) for first 100 samples in 100 events (trigger is approx sample 200) | ## Calculate mean pedestal P<sub>m</sub> & s.d. (σ) for first 100 samples in 100 events (trigger is approx sample 200) | ||
− | ## Set a threshold | + | ## Set a threshold <span style= "color:#333399">P<sub>m</sub> + T<sub>pm</sub></span> (T<sub>pm</sub> ~ 3.5 σ) for further investigation, select events & channels where adc value exceeds this |
#Calculate event pedestal | #Calculate event pedestal | ||
## Calculate event pedestal P<sub>evt</sub> for current event & channel, as mean of 100 samples ending 10 samples before trigger time | ## Calculate event pedestal P<sub>evt</sub> 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 | # 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) | ||
− | ## Select events where adc value goes over a high threshold | + | ## Select events where adc value goes over a high threshold <span style= "color:#333399">P<sub>evt</sub> + T<sub>pe</sub></span> at point x (T<sub>pe</sub> ~ 5sigma)) |
## Find a local pedestal P<sub>loc</sub> as adc value at N<sub>p</sub> upsampled points (minisamples) before x (eg N<sub>p</sub>=15) | ## Find a local pedestal P<sub>loc</sub> as adc value at N<sub>p</sub> upsampled points (minisamples) before x (eg N<sub>p</sub>=15) | ||
# Use local pedestal to find high and low threshold times | # Use local pedestal to find high and low threshold times | ||
− | ## Search forward from x-N<sub>p</sub> to find point x1 where data goes over a slightly less high threshold | + | ## Search forward from x-N<sub>p</sub> to find point x1 where data goes over a slightly less high threshold <span style= "color:#333399">P<sub>loc</sub> + T<sub>h</sub></span> where T<sub>h</sub> ~ 4 σ |
− | ## Search backward from x1 to find point x2 where data goes below low threshold | + | ## Search backward from x1 to find point x2 where data goes below low threshold <span style= "color:#333399">P<sub>loc</sub> + T<sub>l</sub></span> where T<sub>l</sub> ~ σ |
To find where to take local pedestal: | To find where to take local pedestal: |
Revision as of 09:34, 26 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: