The invention relates to a Wien filter provided with electrodes for generating an electric field, and magnetic poles for generating a magnetic field, said electrodes and magnetic poles being positioned around and having a finite length along a filter axis, and being positioned around the filter axis such that electric and magnetic forces induced by the respective fields and exerted on an electrically charged particle moving substantially along the fileter axis at a certain velocity, take substantially an opposite direction to one another and are directed substantially perpendicular to the particle's direction of movement through the filter, said filter having along its axis two ends determined by the finite length of the electrodes and magnetic poles, and said ends both being terminated by a closing plate which is positioned substantially transversely to the filter axis and is provided with an aperture around the filter axis to allow the particle to enter into an exit from the filter. The closing plates are made from a material of low electric and magnetic resistance, and the distance from the closing plates to a plane halfway along and perpendicular to the filter axis is at most approximately equal to the shortest distance from the filter axis to the electrodes and/or magnetic poles.
One embodiment disclosed relates to a Wien filter for a charged-particle beam apparatus. The charged-particle beam is transmitted through the Wien filter in a first direction. A magnetic field generation mechanism is configured to generate a magnetic field in a second direction which is perpendicular to the first direction, and an electrostatic field generation mechanism is configured to generate an electrostatic field in a third direction which is perpendicular to the first and second directions. The field generation mechanisms are further configured so as to have an offset between the positions of the magnetic and electrostatic fields along the first direction. Another embodiment disclosed relates to a Wien filter type device wherein the magnetic force is approximately twice in strength compared to the electrostatic force. Other embodiments are also disclosed.
A MEMS mass spectrometer having metal walls connected between a lid and base, with the walls defining a plurality of interior chambers including sample gas input chambers, an ionizer chamber, a plurality of ion optics chambers and a ion separation chamber. A detector array at the end of the ion separation chamber includes a plurality of V-shaped detector elements positioned along two parallel lines and arranged to intercept all of the ionized beams produced in the mass spectrometer.
