| 摘要 |
PROBLEM TO BE SOLVED: To provide a plasma filter which is capable of separating positive ions from negative ions in multiple kinds of ions and effectively preventing positive ions from recombining with negative ions. SOLUTION: A filter 10 includes a cylindrical chamber 26. Coils 20 surrounding the chamber generate a magnetic field that is aligned parallel to the chamber's longitudinal axis. An electrode 28 generates an electric field that is substantially perpendicular to the magnetic field ExB to create crossing magnetic and electric fields inside the chamber. The inward directed electrode potential of electric field has a negative potential on the longitudinal axis and a substantially zero potential at the wall of the chamber. An injector 18 injects the plasma into the chamber to let the plasma interact with the crossing magnetic and electric fields. With the chamber wall at a distance a from the longitudinal axis, a magnitude BZ for the magnetic field, a negative potential for the electric field of Vctr along the axis and a substantially zero potential at the wall, a cut-off mass to charge ratio is calculated Mc/e =a2 (BZ)2/8Vctr, such that negative ions having a mass M1(-)/e greater than Mc/e will be ejected from the chamber for collection off the chamber wall, while all positive ions will be confined in the chamber for transit through the chamber for collection outside the chamber.
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