...

from pyimgalgos.RadialBkgd import RadialBkgd, polarization_factor

    X, Y, Z = geo.get_pixel_coords()
    rb = RadialBkgd(X, Y, mask, nradbins=500, nphibins=1) 
    pf = polarization_factor(rb.pixel_rad(), rb.pixel_phi()+phi_pf90, 91.33e3)

# in event loop:
    nda, title = rb.subtract_bkgd_interpol(arr * pf) * mask

...

Background subtraction examples

Subtract background shape evaluated in run 192

    from pyimgalgos.GlobalUtils import subtract_bkgd
		# once per run:
        sp.nda_peds  = sp.det.pedestals(runnum)
        sp.nda_bkgd  = sp.det.bkgd(runnum)      # get n-d array with averaged background from calib/.../pixel_bkgd
        sp.nda_smask = sp.det.mask(evt, calib=False, status=True, edges=True, central=True, unbond=True, unbondnbrs=True)


	    #         # windows for background normalization
        winds_bkgd = [(s, 10, 100, 270, 370) for s in (4,12,20,28)] # use part of segments 4,12,20,28 to subtr bkg

        # in the event loop
        nda_raw = sp.det.raw(evt)
        if nda_raw is not None :
            nda =  np.array(nda_raw, dtype=np.float32, copy=True)
            nda -= sp.nda_peds
 
            # Subtract background shape averaged for pure water
            nda = subtract_bkgd(nda, sp.nda_bkgd, mask=sp.nda_smask, winds=sp.winds_bkgd, pbits=0)

...

Radial background subtraction

...

Image corrected up to 80mm, 40<phi< 320:

OLD IMAGE PROCESSING

Subtract background shape evaluated in run 192. 

Averaged Fraser- transformed image using angles from fit to 2 arc peaks

Spectrum of intensities

Spectrum of intensities of all quad 2x1-segment 0 (close to beam) and 4 (water ring region)

before background subtraction

Image AddedImage Added

after background subtraction

Image AddedImage Added

• masked pixels contributes to peak at 0
• 1-, 2- and 3- photon peaks are seen
• common mode correction before background subtraction does not work well in this data sample due to significant fraction of 1-photon peak next to noise peak, which makes an offset due to illumination.
• common mode correction after background subtraction does not work - it moves noise peak to 0 and destroys background subtraction results.
  
  

References

• Mask Editor
•  Calibration Management Tool.
• Radial Background Subtraction Algorithm