MASS SPECTROMETER HAVING MULTI-DYNODE MULTIPLIER(S) OF HIGH DYNAMIC RANGE OPERATION

The invention relates to mass spectrometers having secondary electron multipliers with series of discrete dynode stages. The invention particularly relates to an operation with extended dynamic measuring range and extended lifetime. The invention is based on not adapting the dynamic measuring range by control of the gain of the trans-impedance amplifier, nor controlling the multiplier operating voltage, which both are usually too slow, but alternating a number of active and passive dynode stages of a discrete dynode multiplier. Each dynode stage is connected to a discrete voltage supply circuit, being able to be de-energized and short-cut; the multiplier gain is feedback-controlled by energizing or short-cutting dynode stages, serially from the end of the multiplier, as a function of a last measured ion signal; and the multiplier has a single trans-impedance amplifier and a single analog-to-digital converter, measuring and digitizing the output current of the last active dynode stage.