X-ray analysis apparatus with pulse amplitude shift correction and detector reading circuit means suited for use in such an apparatus

摘要

In a gas ionisation x-ray detector pulse-amplitude shifts will adversely affect the accuracy of the analysis. At increasing count rates a space charge building up leads to a decrease of the impact ionisation in the detector causes the pulse amplitude to become lower. By means of a pulse-shift correction random-access memory count rates pertaining to high-energy parts and low-energy parts, respectively of a peak in a pulse-height distribution are generated. A difference of count rates for a high-energy part and for a low-energy part of the same peak in the pulse-height distribution indicates pulse-amplitude shift. On the basis of the differences of the high-energy count rate and the low-energy count rate a correction signal is produced for adjusting the amplification of the pulse-amplitudes. To obtain stable operation pulse-shift correction is activated only when the count rate exceeds a threshold value.