US 6,719,909 B2 · Band gap plasma mass filter

Abstract

A device and method for selectively establishing predetermined orbits, relative to an axis, for ions of a first mass/charge ratio (m1), requires crossing an electric field with a substantially uniform magnetic field (E×B). The magnetic field is oriented along the axis and the electric field has both a d.c. voltage component (∇Φ0) and an a.c. voltage component (∇Φ1). In operation, voltage Φ0 is fixed to place the ions m1 on confined orbits around the axis when Φ1 is zero. On the other hand, when Φ1 is tuned to a predetermined value, the ions m1 are ejected away from the axis. With E×B established in a chamber, the ions m1 will pass through the chamber when on confined orbits (Φ1=0), and they will be ejected into the wall of the chamber when on unconfined orbits (Φ1=predetermined value).

Claims20

Dependent claims

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 (E×B), and wherein said electric field has a d.c. voltage component (∇Φ0) and an a.c. voltage component (∇Φ1) (E=∇ (Φ0+Φ1);
a means for fixing said d.c. voltage component (∇Φ0) to confine said ions m1 for passage through said chamber and subsequent exit therefrom when said a.c. voltage component (∇Φ1) is substantially zero;
and
a means for tuning said a.c. voltage component (∇Φ1) 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.

3 more elements

A method for selectively establishing predetermined orbits for ions of a first mass/charge ratio (m1) relative to an axis, which comprises the steps of:

crossing an electric field (E) with a substantially uniform magnetic field (B), wherein said magnetic field is oriented along said axis and said electric field is oriented in a substantially radial direction relative to said axis, and further wherein said electric field has a d.c. voltage component (∇Φ0) and an a.c. voltage component (∇Φ1) (E=∇(Φ0+Φ1));
introducing the ions m1 into said crossed magnetic and electric fields;
fixing said d.c. voltage component (∇Φ0) to place said ions m1 in confined orbits around said axis when said a.c. voltage component (∇Φ1) is substantially zero;
and
selectively tuning said a.c. voltage component (∇Φ1) to establish unconfined orbits for ejection of the ions m1 away from said axis when said a.c. voltage component (∇Φ1) has a predetermined value.

2 more elements

Dependencies are inferred from the claim text.

Band gap plasma mass filter

Life of this patent

Band gap plasma mass filter

Life of this patent

Abstract

Claims20