Gate for eliminating charged particles in time of flight spectrometers

摘要

An analysis device such as a time of flight mass spectrometer is disclosed which includes an ICP torch (6) for producing a plasma of bath gas and sample material which is to be analysed. Beam forming optics (13) are provided in order to create a beam of ions of bath gas and ions for delivery to an orthogonal accelerator (17) which pushes out ion packets from the beam. An ion mirror (21) flex the beam towards a detector (24). Arranged between the orthogonal accelerator (17) and the ion mirror (21) is a gate (19) which is formed from a plurality of elements A, B, C, D which are arranged parallel to the direction of beam travel from the orthogonal accelerator to the ion mirror (21). The power supply (28) supplies voltages to the gate (19) so that the elements A, B, C, D create deflection fields for deflecting charged particles sideways so they are not received via the detector (24). The power supply (28) momentarily changes the state of the elements A, B, C, D from time to time so as to selectively remove various charged particles from the beam which will be detected by the detector (24).