CHARGED PARTICLE ANALYSERS AND METHODS OF SEPARATING CHARGED PARTICLES

摘要

A method of separating charged particles using an analyser is provided, the method comprising: causing a beam of charged particles to fly through the analyser and undergo within the analyser at least one full oscillation in the direction of an analyser axis (z) of the analyser whilst orbiting about the axis (z) along a main flight path; constraining the arcuate divergence of the beam as it flies through the analyser; and separating the charged particles according to their flight time. An analyser for performing the method is also provided. At least one arcuate focusing lens is preferably used to constrain the divergence, which may comprise a pair of opposed electrodes located either side of the beam. An array of arcuate focusing lenses may be used which are located at substantially the same z coordinate, the arcuate focusing lenses in the array being spaced apart in the arcuate direction and the array extending at least partially around the z axis, thereby constraining the arcuate divergence of the beam a plurality of times as it flies through the analyser.