Determination and Evaluation of Dead Time for X-Ray Fluorescence Spectrometer

Abstract

When an X-ray photon which is generated by the sample enters into the detector, pulses can be produced and recorded. The detector is unable to respond to another photon that enters at the same time when a photon is being detected. The time that the detector takes to respond to a photon is regarded as dead time. For the x-ray fluorescence detector, the recorded count is less than the real count impulse due to dead time. Hence, to correct x-ray intensity of samples whose element content is vastly different, determination of dead time is necessary. In this paper, a new and complete way to determine dead time is proposed, which can be summarized as “intensity pair method”. Three “intensity pairs” were used for determining dead time, which were “intensity pair” of collimators (S2 and S4), “intensity pair” of spectral lines (Kα and Kβ) and “intensity pair” of beads with different flux-sample ratio (higher SH and lower SL analyte content in the beads). It comes to a conclusion that dead time obtained from “intensity pair” of beads is the most practical method for correcting X-ray fluorescence intensity. As for routine analysis, the dead time of proportional counter can be accurate to 1×10-9s, which can make intensity correction error less than 0.1%.