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 is 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

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