Patent ID: 6939469

Claim:
A band gap mass filter using an azimuthal electric field (E θ ) to separate particles of mass/charge ratio (M 1 ) from particles of mass/charge ratio (M 2 ) in a multi-species plasma which comprises: a plasma chamber defining an axis; at least one direct current (d.c.) coil for generating a substantially constant uniform magnetic field (B 0 ) in said chamber to maintain the multi-species plasma in the chamber; a means for generating an r-f magnetic field in said chamber (B 1 sin ωt), wherein the r-f magnetic field is oriented substantially parallel to the axis to induce the azimuthal electric field (E θ ) in said chamber; and a means for controlling the magnitude (B 1 ) and the frequency (ω) of the r-f magnetic field to place particles M 1 on confined orbits inside said chamber and to place particles M 2 on unconfined orbits inside said chamber to pass the particles M 1 through said chamber for separation of the particles M 1 from the particles M 2 .