Measuring cell for ion cyclotron resonance mass spectrometer
View Patent ↗The invention relates to a measuring cell for an ion cyclotron resonance mass spectrometer (FTMS). The invention provides a measuring cell which, on the one hand, consists of two ion-repelling RF grids at the front ends as trapping electrodes and thus produces a pure cyclotron motion of the ions without the usually co-existing magnetron motion and, on the other hand, measures a multiplied cyclotron frequency by means of a plurality of detection electrodes, whereby either a higher mass accuracy or a shorter measuring time can be achieved.
1. Measuring cell for an ion cyclotron resonance mass spectrometer, comprising
a) end-standing trapping electrodes consisting each of fine structural elements, adjacent structural elements being connected to different phases of a trapping RF voltage, and
b) at least four longitudinal electrodes for the measurement of the image currents.
2. Measuring cell according to claim 1 , wherein the trapping electrodes comprise fine grids made up of real or printed wires, adjacent wires being connected to different phases of the trapping RF voltage.
3. Measuring cell according to claim 1 , with at least four longitudinal electrodes and a switch which can switch the longitudinal electrodes from a mode for exciting the ions to cyclotron motion to a measuring mode for the image currents.
4. Measuring cell according to claim 3 , with eight, twelve or sixteen longitudinal electrodes.
5. Measuring cell according to claim 1 , with at least eight longitudinal electrodes, of which at least four are used solely for detection and at least two longitudinal electrodes positioned opposite each other are used solely to excite the ions to cyclotron motion.
6. Measuring cell according to claim 1 , wherein the structural elements of the trapping electrodes are printed to ceramic, glass, or plastic boards, and wherein a central aperture is spanned by self-supporting real wires.
7. Measuring cell according to claim 6 , wherein the structural elements of the trapping electrodes are divided into fields which roughly can reproduce the potential distribution generated by the excitation electrodes in the central cross-section of the measuring cell, and wherein these electrode fields are charged with mixtures of trapping RF voltages and stepwise attenuated excitation pulses in such a way that the electric excitation fields in the measuring cell are as similar as possible in every cross-section through the measuring cell.
8. An ion cyclotron resonance mass spectrometer, wherein it contains a measuring cell according to claim 1 .
9. Ion cyclotron resonance mass spectrometer according to claim 8 , wherein the RF voltage across the trapping electrodes can be temporarily replaced with DC voltages.
10. Ion cyclotron resonance mass spectrometer according to claim 8 , wherein it incorporates an electron source for the generation of low-energy electrons.
11. Ion cyclotron resonance mass spectrometer according to claim 8 , wherein it incorporates an infrared laser for a multiphoton dissociation.