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 pnCCD1 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