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Product Spotlight
Mass Filter
The Oregon Physics mass filter is an ExB filter that uses orthogonal magnetic and electric fields to filter charged particles by their speed. The device deflects unwanted or extraneous particles from a charged particle beam, while allowing specific particles desired for their mass, charge, or research applications to pass through the filter unaffected.
Developed as part of the Hi5 SIMS project, the Oregon Physics Mass Filter was designed with first order cancellation of chromatic deflection aberrations and higher order, fringe field induced aberrations. The filter accommodates beam energies ranging up to 30keV with three discrete operating modes (off, neutral filter, mass-and-neutral filter).
‘Off’ mode disables the filter and allows all ion masses to get to the target, as well as ions that have lost their charge but retained several keV of kinetic energy and are thus able to reach the target.
‘Neutral filter’ mode prevents energetic neutral particles (primarily generated in the ion source extraction region) from reaching the sample. In this mode, the magnetic field is turned off and the beam is electrostatically deflected through a chicane while the energetic neutral beam is blocked by a filter aperture plate.
A cross-sectional view of the filter, operating as a neutral filter for a 30keV beam, is shown below. The magnetic field is set to zero and the plates are biased to offset the beam by ~0.02” (~500um).
‘Mass and neutral filter’ mode operates with balanced electric and magnetic deflection fields for a particular mass-to-charge ratio of the selected ion beam. This mode filters out the energetic neutrals and allows only a single, specific ion mass to pass through to the target. More precisely, only ions with a particular mass/charge (m/q) are allowed to pass through the filter, however, ions generated in the plasma are primarily singly ionized. The degree of electrostatic deflection determines the range of ion masses that can be selected and the resultant resolving power of the mass filter. Since the beam still travels along a similar chicane pathway as it does in neutral filtering mode, the neutral particles are also filtered out. When operating in this mass-and-neutral filtering condition, there are two software modes available that allow the user to choose between high or low mass resolution modes.
Oregon Physics mass filters are available for purchase in limited quantity. To inquire, please contact us.