Patent ID: 6719909
Filing Date: 2004-04-13
Classification: H01J

Abstract:
A band gap plasma filter for selectively passing ions of a first mass/charge ratio (m1) therethrough, wherein m1 is less than a predetermined cut off mass, Mc, said filter comprising:a means for introducing a plasma, including said ions m1, into a hollow, substantially cylindrical-shaped chamber, said chamber defining an axis and being surrounded by a wall; a magnetic means for establishing a substantially uniform magnetic field (B), said magnetic field being oriented along said axis in said chamber; a means for creating an electric field (E), wherein said electric field is oriented in a substantially radial direction relative to said axis to cross with said magnetic field (EÃ—B), and wherein said electric field has a d.c. voltage component (âˆ‡&PHgr;0) and an a.c. voltage component (âˆ‡&PHgr;1) (E=âˆ‡ (&PHgr;0+&PHgr;1); a means for fixing said d.c. voltage component (âˆ‡&PHgr;0) to confine said ions m1 for passage through said chamber and subsequent exit therefrom when said a.c. voltage component (âˆ‡&PHgr;1) is substantially zero; and a means for tuning said a.c. voltage component (âˆ‡&PHgr;1) to eject said ions m1 from said chamber and into collision with said wall thereof to prevent passage of said ions m1 through said chamber.