Content

Algorithms

In this note we discuss common mode correction algorithms implemented in psana module ImgAlgos::NDArrCalib.

We use algorithms earlier developed for CSPADs from ImgAlgos::GlobalMethods(#1) and from psalg package (#2 and #3).

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

#1 - common mode peak finding algorithm

common_mode parameters for CSPAD and CSPAD2x2

1 50 50 100

par[0] - algorithm #
par[1] - maximal deviation of the peak mean from 0
par[2] - maximal allowed value of the peak RMS
par[3] -threshold on number of pixels in the ADU bin in the peak finding algorithm

for other detectors

par[4] - number of segments for common mode evaluation
par[5] - segment size (number of pixels for common mode evaluation)
par[6] - stride (step for jump to the next pixel)
For example:
```
1 50 50 100 8192 128 1
```

#2 - MEAN evaluation

par[0] - algorithm #
par[1] - maximal threshold on intensity to evaluate mean for low intensities
par[2] - maximal allowed common mode correction
par[3] - length of consecutive pixel array for common mode evaluation
For example, for pnCCD
```
1 1000 1000 128
```

#3 - MEDIAN evaluation

Parameters are the same as in #2

Test of the common mode correction for pnCCD

To test implementation of algorithms in ImgAlgos::NDArrCalib we use the same data sets as in 2014-03-25-Ankush-CommonModeNoise.pdf

Use data from experiment amob5114

High gain pnCCD run 121

2(or 3) 1000 1000 128

Spectra for 1) raw data, 2) subtracted pedestals, 3) subtracted common mode correction algorithm #2 and 4) algorithm #3:

Images 1) for subtracted pedestals and 2) common mode correction algorithm #2:

High gain pnCCD run 329

2(or 3) 1000 1000 128

Spectra for 1) raw data, 2) subtracted pedestals, 3) subtracted common mode correction algorithm #2 and 4) algorithm #3:

Images 1) for subtracted pedestals and 2) common mode correction algorithm #2:

Summary for pnCCD

Common mode correction for pnCCD

gives significant effect in low gain mode and is negligible in high gain mode
algorithm #2 gives the best results, #3 a little bit worse, #1 - does not work for pnCCD

Test of common mode correction for CSPAD

Use cxi83714-r0136 with

1 10 10 100

Spectra for 1) raw data, 2) subtracted pedestals, 3) subtracted common mode correction algorithm #1:

Images 1) for subtracted pedestals and 2) common mode correction algorithm #1:

Summary for CSPAD

Common mode correction for CSPAD works with algorith #1 and shows significant effect.

Test of common mode correction for CSPAD2x2

Use meca1113-r0045 with

1 50 10 (100) - last parameter is set by default