Calibration of the MIMOSA5 ladder

9/28/2005 H. Wieman

A MIMOSA5 ladder ADC has been calibrated using shot noise. The was done for 20 pixels on one of the MIMOSA5 chips mounted on the ladder. The measurement was done by recording 4 frames following reset for a variety of light levels. A derivation of how this works can be found at:

http://www-rnc.lbl.gov/~wieman/CalibrationByShotNoise.htm

This is done by plotting the variance in (ADC counts)² as a function of ADC counts. The calibration is taken from the slope. The line below used for this calibration was fit to the 4 lowest clusters. The three colors of points, red, green and blue correspond to the 3 CDS samples obtained from the 4 frame reads. The points that lie away from the line are from data near the limits of the ADC, so this may be due to non-linearity of the ADC/DAQ system. But, this remains to be verified. The last cluster (ADC = ~200) is missing the green points because the last frame read at this larger light setting already exceeded the ADC range.

plotted in red below

baseline noise e-rms

electrons per ADC count