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Most of pixel array detectors produce imaging data which that can not directly be directly used in analysis and need in corrections. Most popular corrections are

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In this note we discuss common mode correction algorithms. Common mode is a tiny hardware effect of collective pixel intensity variation due to synchronous variation of potentials on sensor chip or ADC at readout process. This effect can be corrected at low sensor illumination, where the number of pixels with energy deposition from photons is small. The spectrum of pixel intensities without photon photons should be grouped in the peak with small offset of the average from zero (after if the dark rate correction is already applied) due to the common mode effect. This offset can be evaluated and subtracted from all pixel intensities in the group of synchronously fluctuating pixels. This correction is detector-dependent, because detectors may have many ADCs working on different groups of pixels. Algorithms are also detector-dependent in order to better account for sensor behaviour. 

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where keywords do_peds and do_cmod should have value yes or true in order to turn on pedestal subtraction and common mode correction algorithms. Each algorithm may load file with parameters from calib calibration directory, which by default isaccounts for experimnet, calibration version, data source, calibration type and run range:

/reg/d/psdm/<INS>/<experiment>/calib/<calib-version>/<data-source>/<calibration-type>/<run-range>.data
    for 
For example:
/reg/d/psdm/XPP/xppi0614/calib/Epix100a::CalibV1/NoDetector.0:Epix100a.0/pedestals/0-end.data
/reg/d/psdm/XPP/xppi0614/calib/Epix100a::CalibV1/NoDetector.0:Epix100a.0/common_mode/0-end.data

Content of this file depends on calibration type and algorithm, as shown below.

Algorithms

We In module ImgAlgos::NDArrCalib we use algorithms earlier developed for CSPADs from ImgAlgos::GlobalMethods(#1) and from psalg package (#2 and #3)CSPAD and other detectors and currently residing in ImgAlgos and psalg packages.

Selection of algorithm for particular device can be of particular type is controlled by the parameters in file for common_mode calibration type of calibration constants.

#1 - common mode peak finding algorithm

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