Activity of the Ru-source.
To perform a calibration, a known charge is injected into the front end electronics.
For a range of threshold values the efficiency of the detector and electronic
is measured. The efficiency versus the threshold is then fitted with a s-curve
(complimentary error function) to extract the median (50 % point of efficiency)
and the sigma (with represents the noise). These values are calculated for
several input charges. The response of the detector board can then be obtained
by fitting the median value vs the injected charge with a response function to
relate the threshold (in mV) to a detector signal (collected charge in fC).
A more detailed description of this method can be found here.
Calibrations were performed at double sided silicon detectors at two beam test at KEK - the results are available on this server: