METHOD AND APPARATUS FOR SPATIAL SEPARATION OF AC AND DC ELECTRIC FIELDS, WITH APPLICATION TO FRINGE FIELDS IN QUADRUPOLE MASS FILTERS

摘要

Abstract of the DisclosureMethods and apparatus for spatially separating AC and DC electricfringe fields near the ends of quadrupole mass filters which involve use ofmaterials with electric properties that function as dielectrics to the ACfields and as conductors to the DC fields. Devices constructed of such mate-rials shield against DC fringe fields, but not against AC fringe fields.Such devices include a small shield in the form of a tube or other appropriateconfiguration disposed coaxially with the axis of the mass filter at eitheror both ends thereof. A good dielectric is used as the supporting structureand a thin conductive or semi-conductive layer is applied thereto whichfunctions as the shield.