Miniature cylindrical ion traps and arrays

A quadrupole ion trap mass analyzer with simplified geometry, the cylindrical ion trap (CIT), was shown to be well-suited to use in miniature mass spectrometers and even mass spectrometer arrays. Experiments with a single miniature CIT showed acceptable resolution and sensitivity, limited by the ion trapping capacity of the miniature device. Parallel miniature CIT arrays, with each CIT of the same size, were operated with the same rf and ac voltages applied to all of the CITs in the array. In this mode of operation, the array was shown to increase ion trapping capacity and thus sensitivity, compared to a single miniature CIT. Parallel miniature CIT arrays with each CIT of a different size were also examined. In this type of array, each CIT was operated to trap a single mass-to-charge ratio without the need to ramp the rf voltage. A multiple-ion monitoring experiment can be performed in the array, and the rf voltage necessary for operation is simplified and greatly reduced in amplitude. Because of the reduced rf voltage, this type of array is suitable for a fully miniaturized mass spectrometer system that operates under size and power restrictions. Further improvements were also made to improve the resolution of miniature CITs by use of nonlinear resonance ejection, which also facilitated operation with air, instead of helium, as the buffer gas. Non-destructive image current detection in a full sized CIT was also performed. In addition, an improved method of image current detection, differential detection was demonstrated in a hyperbolic ion trap. This new method gives increased signal intensity as well as reduced noise