The United States of America As Represented by the Administrator of the

United States of America As Represented by the Administrator of Nasa

Robert F Roman

Arthur N Curren

Kenneth A Jensen

James S Sovey

Michael J Mirtich, Jr

Vincent K Rawlin

The present invention is directed to a method and apparatus for producing a highly-textured surface on a copper substrate with only extremely small amounts of texture-inducing seeding or masking material. The texture-inducing seeding material is delivered to the copper substrate electrically switching the seeding material in and out of a circuit loop.

Substrate with low secondary emissions

Method and apparatus for producing a substrate with low secondary

A very thin layer of highly textured carbon is applied to a copper surface by a triode sputtering process. A carbon target 10 and a copper substrate 12 are simultaneously exposed to an argon plasma 14 in a vacuum chamber. The resulting carbon surface is characterized by a dense, random array of needle-like spires or peaks which extend perpendicularly from the copper surface. The coated copper is especially useful for electrode plates in multistage depressed collectors.

Textured carbon surfaces on copper by sputtering

An improved ion thruster (10) for low specific impulse operation in the 1500 sec to 6000 sec range has a multicusp boundary field (48) provided by high strength magnets (30-38) on an iron anode shell (14) which lengthens the paths of electrons from a hollow cathode assembly (20). A downstream anode pole piece in the form of an iron ring (40) supports a ring of magnets (44) to provide a more uniform beam profile. A cylindrical cathode magnet (46) can be moved selectively in an axial direction along a feed tube (22) to produce the desired magnetic field at the cathode tip (24).

Ring-cusp ion thruster with shell anode

A source of hydrogen ions is disclosed and includes a chamber having at one end a cathode which provides electrons and through which hydrogen gas flows into the chamber. Screen and accelerator grids are provided at the other end of the chamber. A baffle plate is disposed between the cathode and the grids and a cylindrical baffle is disposed coaxially with the cathode at the one end of the chamber. The cylindrical baffle is of greater diameter than the baffle plate to provide discharge impedance and also to protect the cathode from ion flux. An anode electrode draws the electrons away from the cathode. The hollow cathode includes a tubular insert of tungsten impregnated with a low work function material to provide ample electrons. A heater is provided around the hollow cathode to initiate electron emission from the low work function material.

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Brook Park, OH, United States of America

Robert F Roman