Patent ID: 8109928

Claim:
A plasma-generating device comprising: an anode; a cathode having a tapered portion narrowing toward the anode; a tubular insulator extending along and surrounding a portion of the cathode and having a distal end; one or more intermediate electrodes electrically insulated from each other and from the anode, a plasma chamber having a substantially cylindrical portion, the cylindrical portion of the plasma chamber being formed by at least one of the intermediate electrodes; a plasma channel having an inlet at a distal end of the plasma chamber, the plasma channel extending longitudinally through a hole in the anode and having an outlet opening at a distal end of the anode, a part of the plasma channel being formed by at least one of the intermediate electrodes; wherein an end of the cathode extends longitudinally into the plasma chamber to some distance away from the inlet of the plasma channel, and wherein the tapered portion of the cathode projects only partially beyond the distal end of the insulator.