Dead‐time correction of synchrotron radiation‐based XRF measurements at decaying storage ring current

Strong requirements due to the certification of reference materials or to lowering substantially the limits of determination of elements may require the analyst using XRF at a synchrotron beamline to carry out very long measurements, especially during unattended night runs. In this case, the problem of correction of the combined effect of the exponentially decaying fluorescence radiation, caused by the diminishing electron current of the storage ring, and the resulting time‐dependent dead‐time fraction of the spectrometer has to be faced. This effect cannot be treated solely by dead‐time meter or by beam monitor and will deteriorate the quantitative correctness of the analytical results. Fortunately, the exponential behaviour of the irradiating beam transfers to all components of the fluorescence spectrum. Therefore, it is possible to obtain an analytical solution for the time integral of the measurement. The equation is identical with that found for the dead‐time affected measurement of a pure short‐lived isotope. Graphs for correcting the apparent peak pulse rates in order to obtain true rates at the beginning of the measurement and for error propagation of half‐life and dead‐time are presented. As the case of non‐extended dead‐time was dealt with, the correction of extended dead‐time will have to be treated in the future. Copyright © 2005 John Wiley & Sons, Ltd.