부산대학교 도서관

Measurement campaigns of the Max-Planck Advanced Study Group (ASG) in cooperation with the Center for Free Electron Laser Science (CFEL) at DESY-FLASH and SLAC-LCLS have established pnCCDs as universal photon imaging spectrometers in the energy range from 90 eV to 2 keV. In the CFEL-ASG multi purpose chamber (CAMP), pnCCD detector modules are an integral part of the design with the ability to detect photons at very small scattering angles. In order to fully exploit the spectroscopic and intensity imaging capability of pnCCDs, it is essentially important to translate the unprocessed raw data into units of photon counts for any given position on the detection area. We have studied the performance of pnCCDs in FEL experiments and laboratory test setups for the range of signal intensities from a few X-ray photons per signal frame to 100 or more photons with an energy of 2 keV per pixel. Based on these measurement results, we were able to characterize the response of pnCCDs over the experimentally relevant photon energy and intensity range. The obtained calibration results are directly relevant for the physics data analysis. The accumulated knowledge of the detector performance was implemented in guidelines for detector calibration methods which are suitable for the specific requirements in photon science experiments at Free Electron Lasers. We discuss the achievable accuracy of photon energy and photon count measurements before and after the application of calibration data. Charge spreading due to illumination of small spots with high photon rates is discussed with respect to the charge handling capacity of a pixel and the effect of the charge spreading process on the resulting signal patterns.