Silicon Detector Calibration

Other than the proportional counter, which really counts incident photons (electric pulses), the segmented silicon detector works like a photodiode whose current is integrated during the pixel dwell time. The integrated charge will translate to a voltage which is read by the analog-to-digital converter in the microscope server computer. Moreover, even without incident x rays, the leakage current of the silicon chip will lead to a certain signal. Therefore, a rather involved detector calibration is necessary to subtract the dark signal and to convert to a photon count rate. The theoretical background of the detector calibration can be found in Michael Feser's thesis [1, Chap. 3.4], and the practical aspects are described in more detail in the Silicon Detector Manual, which you can find on http://xray1.physics.sunysb.edu/user/manuals.php. Here, we give a short summary.