SI(LI) DETECTOR EFFICIENCY AND PEAK SHAPE CALIBRATION IN THE LOW-ENERGY RANGE USING SYNCHROTRON-RADIATION

The efficiency and pulse distribution characterization of an Si(Li) de tector (SLD) were obtained using the monochromatized Super-AGO (LURE, Orsay, France) synchrotron beam, The selected energies ranged from 700 to 7000 eV and the radiation intensity was successively measured with a proportional counter, used as a reference, then with the detector t o be calibrated, More than 100 experimental points were recorded; step s as small as 1 eV were used to examine carefully the silicon and gold absorption edges, The SLD spectra were processed using the COLEGRAM d econvolution software, which fits different theoretical functions to e xperimental data, The processing includes a least-squares fitting with the Marquart-Levenberg algorithm and the use of a Hypermet-type funct ion, the sum of a main Gaussian function with a low-energy tail. The p roportional counter efficiency curve is calculated using attenuation c oefficients for the polypropylene window and argon-methane counter gas , The complete SLD peak shape calibration was obtained: the variation of each fitting function parameter with energy is shown, The tailing p arameters show sharp discontinuities that can be linked to different i nteraction points in the detector front end, This detector pulse distr ibution calibration obtained with monochromatized radiation could be u sed to process accurately usual X-ray spectra including several peaks and satellites, The uncertainty in the SLD efficiency calibration poin ts is about 3%,The experimental values were fitted with a theoretical function describing the transmission through different absorbing layer s, It is seen that the so-called silicon 'dead layer' acts as a partia lly active layer, the corresponding events being recorded in the peak tail. (C) 1997 by John Wiley & Sons, Ltd.