National Synchrotron Light Source and Materials Science Department Seminar

Silicon Drift Detector type detectors (SDDs, pnCCDs, CDDs and active pixel sensors(APS), DEPFETs) have been developed as high speed spectrometers for energies from 50 eV up to 50 keV in a single photon counting mode as well in an integration mode. They show high energy and high position resolution as well as high quantum efficiency for X-rays. Their full well capacities are larger than 105 electrons per pixel. The read noise close to room temperature is less than 10 electrons (rms) leading to Fano limited energy measurements at readout speeds of 108 pixels per second. Pixel sizes of 20 × 20 µm2 have been realized on 500 µm fully depleted silicon as well as pixel sizes up to 1 cm2. Typical formats being experimentally evaluated are 256 × 256 or 512 × 512 with pixel sizes from 35 µm to 75 µm. The typical sensitive detector thickness is 500 µm, a maximum detector thickness is technologically limited to 1.5 mm.

Special designs have been proposed for synchrotron applications complying with the time structure (bunch structure) conditions of the recently approved XFEL to be built at DESY. They are based on the concept of a (non-controlled) controlled drift detectors.

A detector system which satisfies the LCLS specifications is presented on the basis of fully depleted pnCCDs with a format of 1024 x 1024 and a pixel size of 50 µm and a readout rate of 250 Hz.