where q is the amount of charge created by the photocathode per detected gamma-ray, I is the average photocurrent
per detector and [f.
are measured in a standard three-electrode cell before and after surface modification.
However, the proportionality constant connecting the photocurrents
to the beam current may vary by a percent or more over an hour due to heating of optics, variations in the synchrotron beam position, etc.
The photodiodes convert the RGB light components into photocurrents
, and the transimpedance amplifiers then convert the photocurrent
to analog voltages.
The ratios of these photocurrents
as a function of the angular position of the movable electron spectrometer provided the data necessary to determine the polarization of the light.
Any imbalance between the photocurrents
generated by the reference and signal detectors, however, is amplified.