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A fluid jet assisted ion projection and printing apparatus wherein substantially equal numbers of positive and negative ions are generated simultaneously during a series of RF arc breakdowns which take place within a fluid transport channel passing through the body of the apparatus. The rapidly movi

A fluid jet assisted ion projection and printing apparatus wherein substantially equal numbers of positive and negative ions are generated simultaneously during a series of RF arc breakdowns which take place within a fluid transport channel passing through the body of the apparatus. The rapidly moving fluid stream, passing through the channel, transports the ions which may be allowed to pass out of the body or may be neutralized within the body by ion modulation electrodes within the channel. Ions of a selected sign may be accelerated toward and deposited, in an imagewise pattern, upon a relatively moving charge receptor.

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1. A fluid jet assisted electrographic marking apparatus for placing electrostatic charges upon a charge receptor in an imagewise pattern, said apparatus being characterized by including means for supplying a transport fluid, housing means defining a channel therethrough, said channel being elon

1. A fluid jet assisted electrographic marking apparatus for placing electrostatic charges upon a charge receptor in an imagewise pattern, said apparatus being characterized by including means for supplying a transport fluid, housing means defining a channel therethrough, said channel being elongated in a direction transverse to the direction of movement of the transport fluid, through which the transport fluid may be directed to the charge receptor, said housing including an ion generation portion and an ion modulation portion, each portion being adjacent to said channel, and wherein said ion generation portion includes ion generating means located adjacent said channel and extending along the length of said channel for initiating a continuous series of RF arc discharges within said channel, for simultaneously creating a uniform supply of positive and negative ions along the length of said channel, directly in the transport fluid moving within said channel, and said ion modulation portion includes modulation means located adjacent said channel comprising a plurality of spaced, conductive, modulating electrodes on one side of said channel, a conductive member on the side of said channel opposite to said modulating electrodes, a source of modulating potential, switch means for selectively connecting said source of modulating potential to each of said modulating electrodes, and a second source of reference potential connected to said conductive member, whereby each of said modulating electrodes controls the passage of a beam of ions from said channel when its respective switch is energized. 2. The fluid jet assisted electrographic marking apparatus as defined in claim 1 characterized in that said ion generation portion comprises a dielectric body, and said ion generating means comprises a first conductive electrode embedded in said dielectric body adjacent said channel, an RF voltage source connected to said first electrode, a second conductive electrode located adjacent said channel and exposed to said transport fluid, and a source of reference potential connected to said second electrode. 3. The fluid jet assisted electographic marking apparatus as defined in claim 2 characterized in that said second electrode is supported by said body adjacent the entrance of said channel. 4. The fluid jet assisted electographic marking apparatus as defined in claim 3 characterized in that said first electrode comprises a platinum wire and said second electrode comprises a strip of platinum foil. 5. The fluid jet assisted electrographic marking apparatus as defined in claim 2 characterized in that said first electrode is located within a groove in said dielectric body, said groove extending into said body from said channel wall, dielectric filler material fills said groove between said first electrode and said channel wall, and said dielectric body, said first electrode and said dielectric filler material each have substantially the same coefficient of thermal expansion. 6. The fluid jet assisted electrographic marking apparatus as defined in claim 5 characterized in that said dielectric body and said dielectric filler material are inorganic materials. 7. The fluid jet assisted electrographic marking apparatus as defined in claim 1 characterized in that said ion generation portion comprises a dielectric body and said ion generating means comprises a first conductive electrode embedded in said dielectric body adjacent said channel, an RF voltage source connected to said first electrode, a second conductive electrode embedded in said dielectric body, a source of reference potential connected to said second electrode, and field concentrating means located adjacent said channel and exposed to said transport fluid, is associated with said second conductive electrode. 8. The fluid jet assisted electrographic marking apparatus as defined in claim 7 characterized in that said second electrode is located on the opposite side of said channel. 9. The fluid jet assisted electrographic marking apparatus as defined in claim 7 characterized in that said first and second electrodes are each located within a groove in said dielectric body, dielectric filler material fills each of said grooves, and said dielectric body, said first electrode, said second electrode and said dielectric filler material comprise inorganic materials having substantially the same coefficient of thermal expansion. 10. The fluid jet assisted electrographic marking apparatus as defined in claim 1 characterized in that dielectric interface means is located between said ion generation portion and said ion modulation portion. 11. The fluid jet assisted electrographic marking apparatus as defined in claim 10 characterized in that electrically conductive interface means is located between said ion generation portion and said dielectric interface means, and a second source of reference potential is connected to said conductive interface means. 12. A method for placing electrostatic charges upon a charge receptor in an imagewise pattern, by means of a fluid jet assisted electrographic marking apparatus, said method being characterized by including the steps of supplying a transport fluid directing the transport fluid to the charge receptor through an elongated channel in the electrographic marking apparatus, initiating a continuous series of RF arc discharges within the channel and uniformly along its length for simultaneously creating a uniform supply of positive and negative ions along the length of said channel, directly in the transport fluid moving within the channel, entraining the positive and negative ions within the transport fluid moving within the channel, and controlling the passage of ions exiting from the channel with a series of modulating electrodes, by addressing respective modulating electrodes for either passing or inhibiting the passage of selected beams of ions from the channel. 13. The method for placing electrostatic charges upon a charge receptor in an imagewise pattern, by means of a fluid jet assisted electrographic marking apparatus, as defined in claim 12 said method being characterized in that the transport fluid is air and said step of initiating RF arc discharges comprises the steps of imposing an RF voltage on an insulated electrode positioned in the vicinity of the channel, inducing uniform polarization charges on the insulating surface adjacent the electrode, inducing opposite charges on the surface of a spaced field electrode, and causing ion generating air breakdown to occur within the channel when the field between the opposite charges on the insulating surface and the field electrode becomes high enough. 14. The method for placing electrostatic charges upon a charge receptor in an imagewise pattern, by means of a fluid jet assisted electrographic marking apparatus, as defined in claim 12 said method being characterized in that said step of initiating RF arc discharges is cyclical and self quenching. 15. A fluid jet assisted ion projection apparatus for placing electrostatic charges upon a charge receptor, said apparatus being characterized by including means for supplying a transport fluid, and housing means defining a channel therethrough, said channel being elongated in a direction transverse to the direction of movement of the transport fluid, through which the transport fluid may be directed to the charge receptor, said housing including ion generating means, located adjacent said channel, and extending along the length of said channel for initiating a continuous series of RF arc discharges within said channel, for simultaneously creating a uniform supply of positive and negative ions along the length of said channel, directly in the transport fluid moving within and through said channel. 16. The fluid jet assisted ion projection apparatus as defined in claim 15 characterized in that said ion generation means comprises a dielectric body, a first conductive electrode embedded in said dielectric body adjacent said channel, an RF voltage source connected to said first electrode, a second conductive electrode exposed to said fluid adjacent said channel, and a second source of reference potential connected to said second electrode. 17. The fluid jet assisted ion projection apparatus as defined in claim 16 characterized in that said second electrode is supported by said body adjacent the entrance of said channel. 18. The fluid jet assisted ion projection apparatus as defined in claim 16 characterized in that said first electrode is located within a groove in said dielectric body, said groove extending into said body from said channel wall, dielectric filler material fills said groove between said first electrode and said channel wall, and said dielectric body, said first electrode and said dielectric filler material each have substantially the same coefficient of thermal expansion.