High performance gridless ion mirrors for multi-reflection time-of-flight and electrostatic trap mass analyzers

Abstract

The paper summarizes original developments of gridless ion mirrors for high-resolution multi-reflection time-of-flight mass spectrometers (MR TOF MS). Optimized mirror geometries and electrostatic field distributions reach up to the 5th order isochronicity with respect to the energy spread and up to the 3rd order full isochronicity per energy, spatial and angular spreads of ion packets. Using a retarding focusing field at the mirror entrance doubles the ion transport energy at limited highest voltages. In planar analyzers with a zig-zag ion path, quasi-planar mirrors eliminate the 2nd order dependence of the flight time on the ion packet width in the drift direction. Improved MR TOF analyzers of 1 m size provide well over one million aberration limit at realistic ion packets parameters past orthogonal accelerators. Because of high order isochronicity the aberration limit rapidly grows with the analyzer size or when using narrower ion packets. In experiments, improved analyzers with one meter size demonstrate up to 300 000 mass resolving power at the full mass range and 500 000 at the restricted mass range. Improved ion mirrors with two-dimensional electrostatic fields are applicable for TOF MS, electrostatic traps and open electrostatic traps in planar and hollow cylindrical geometries.