THE CORRECTION OF THE DEAD-TIME LOSS OF THE GE DETECTOR IN X-RAY-ABSORPTION SPECTROSCOPY

The effects of dead time loss of the 13 element Ge detector (Canberra, GL0110), which result from the associated electronics, were studied. Distortions and noise attributable to dead-time losses are found to be substantial even for dilute metalloprotein samples and modest count rates. The dead time loss can introduce two types of non-linear problems into the X-ray Absorption Fine Structure (XAFS) data collection. First, the I0 fluctuation cannot be fully divided out; second, XAFS spectra for concentrated samples can be substantially reduced. The dead time loss calibration showed that the response of the system can be better approximated by the first order approximation of the paralysable and the non-paralysable models rather than the two models themselves. The dead time correction using this algorithm produces satisfactory results with the correction error generally within the statistical error of photon counting. This will permit reliable XAFS data collection at high Incident Count Rate greatly improving the counting efficiency. The dependences of the dead time and the energy resolution on the shaping time of the shaping amplifier were also examined.