Patent ID: 8337494

Claim:
A plasma-generating device comprising: a. an anode at a distal end of the device, the anode having a hole therethrough; b. a plurality of intermediate electrodes electrically insulated from each other and from the anode, each of the intermediate electrodes having a hole therethrough, wherein the holes in the intermediate electrodes and the hole in the anode form a hollow space having i. a first portion, which over a substantial length of this portion has a uniform first cross-sectional area, and ii. a second portion, which over a substantial length of this portion has a uniform second cross-sectional area that is smaller than the first cross-sectional area, the second portion being downstream of the first portion; c. a cathode having a tapered distal portion narrowing toward a distal end of the cathode, a proximal end of the tapered portion being a base of the tapered portion, the tapered portion having a length being a distance from the base of the tapered portion to the distal end of the cathode; and d. an insulator sleeve extending along and surrounding only a portion of the cathode and having a distal end, wherein only a part of the tapered portion of the cathode projects beyond the distal end of the insulator sleeve into the first portion of the hollow space, and wherein a distal end of the cathode is located some distance away from a proximal end of the second portion of the hollow space.