Plasma-generating device having a throttling portion

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, at least in part, form a hollow space having
• i. a first portion having a throat, the throat having a first cross-sectional area,
• ii. a second portion, which over a substantial length of this portion has a uniform second cross-sectional area larger than the first cross-sectional area, the second portion being formed by two or more of the intermediate electrodes, the second portion being upstream of the first portion,
• iii. a third portion, which over a substantial length of this portion has a uniform third cross-sectional area larger than the first cross-sectional area, the third portion, at least in part, being formed by the anode, the third portion being downstream of the first portion;
• c. a cathode having a tapered portion;
• and
• d. an insulator sleeve extending along and surrounding a substantial portion of the cathode,
• wherein an inside surface of the insulator sleeve and an outside surface of the cathode form a gap, the gap being in communication with the hollow space.