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Code Block
def peakIsSelected() :
    """Apply peak selection criteria to each peak from file
    """
    amax, atot, npix, x, y, r, phi = sp.amax, sp.atot, sp.npix, sp.x, sp.y, sp.r, sp.phi
    if amax<150  : return False
    if atot<2500 : return False
    if npix<30   : return False
    if r<434     : return False
    if r>444     : return False
    if phi<150 and phi>-150 : return False
    return True

 

  

Few sets of parameters listed in table were tested in order to justify selection parameters.

ParameterSel.1 (rpeak5)Sel.2 (rpeak7)Sel.3 (rpeak3)
in module NDArrDropletFinder:Arc
threshold_low
101010
threshold_high
100100150
peak_radius
573
in method peaks_filter(...)
atot_thr
200020002000
npix_thr
203020
npeaks_min
111
npeaks_max
102010
Save selected peaks in file
Process peaks from file
selector in method peakIsSelected()
amax
150150150
atot
2500
2500
2500
npix
30204020
rmin
434434434
rmax444444444
phi
<-150 & >150<-150 & >150<-150 & >150

 

Sel.1 (rpeak=5):

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Sel.2 (rpeak=7):

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Sel.3 (rpeak=3):

Plots for selection parameters

Distribution for selection parameters are shown below. The 1st group of plots is accumulated for all peaks saved in the file with list of peaks:

  • phi - azimuths angle [degree] of the peak, evaluated as atan2(y,x)
  • Amax - maximal pixel intensity [ADU]
  • Atot - total peak intensity [ADU] for all pixels at the distance in x and y less or equal than peak_radius (peak region)
  • Npix - number of pixels in the peak region with intensity above threshold_low
  • r - peak radius, evaluated as sqrt(x*x + y*y)
  • Npeaks - number of peaks in the arc region after peak-finder after

Two other plots were accumulated after  method peakIsSelected() is applied

  • Npeaks selected - number of peaks in the event
  • Distance - between two peaks [pixels] in the event which has two selected peaks only
Sel.1 (rpeak=5):

Image AddedImage AddedImage AddedImage AddedImage AddedImage AddedImage Added Image Added

These distributions were obtained for "reasonable-by-eye" selection criteria. Now the question is how optimal the selection parameters are?

 

Sel.2 (rpeak=7):

Image AddedImage AddedImage AddedImage AddedImage AddedImage AddedImage Added  Image Added

These plots look noisy, because it was allowed to save up to 20 peaks in the event.

Sel.3 (rpeak=3):

Image AddedImage AddedImage AddedImage AddedImage AddedImage AddedImage AddedImage Added

Tight parameters in this case reduce a number of signal events in the Distance distribution.

Optimal parameters

  • peak_radius = 3, 5, 7 - or peak region sixe 7x7, 11x11, 15x15, respectively does not show significant influence on figure of merit (FOM) distance distribution. Keep 5 as golden-medium.
  • amax and atot show significant increase in number of peaks for <150 and <2500, respectively. These selection criteria do not decrease a signal peak in FOM. To be safe we may still pre-select peaks  with  amax<100 and atot<2000 and then apply tight selection later.
  • npix -it is safe to require >20 or >30.

  • r - chosen range 434 ≤ r ≤ 444 looks optimal
  • npeaks_max is less than 6 after selection. It looks safe to constrain npeaks_max = 10. Used 20 adds too much noise.

So far original Selection 1 looks optimal.

 

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References

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