METHOD AND APPARATUS FOR DETERMINING A MOBILITY OF IONS

摘要

A method and an apparatus for determining a mobility of ions. The method includes the steps of modulating an ion beam with an ion gate which is controlled by a modulation function for generating a modulated ion beam, of guiding the modulated ion beam through a drifting region, of measuring a signal of the modulated ion beam after the modulated ion beam has passed the drifting region and of calculating a correlation of the modulation function and the signal in order to determine the mobility of the ions. The apparatus includes the ion gate, the drifting region through which the modulated ion beam is guidable, a detector by which the signal of the modulated ion beam is measurable after the modulated ion beam has passed the drifting region and a calculation unit by which the correlation of the modulation function and the signal is calculable in order to determine the mobility of the ions. An autocorrelation of the modulation function is a two-valued function.

主权项

1. A method for determining a mobility of ions, including the steps of:
modulating an ion beam with an ion gate which is controlled by a modulation function for generating a modulated ion beam, wherein said modulation function is a pseudorandom sequence generated with a linear feedback shift resister and wherein an autocorrelation of said modulation function is a two-valued function, guiding said modulated ion beam through a drifting region, measuring a signal of said modulated ion beam after said modulated ion beam has passed said drifting region, calculating a correlation of said modulation function and said signal in order to determine said mobility of said ions, wherein an interval of interest of possible ion drift times is chosen from said correlation and in that the method comprises a step of selecting said modulation function by selecting a tap set of said linear feedback shift register such that as many as possible false peaks in said correlation are located outside of said interval of interest.