The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Jun. 26, 1990
Filed:
Oct. 17, 1988
Donald Grim, Renton, WA (US);
Paul G Lichon, Bothell, WA (US);
The Boeing Company, Seattle, WA (US);
Abstract
An ion thruster for accelerating positively charged ions produced by the collision of free electrons with gas atoms. An ion thruster (10,100) includes a cathode chamber (12, 60, 118) and an ionization chamber (14, 106). The outer surface of an emitter tube (28, 61, 128) is coated with a dielectric material to protect the emitter tube from sputtering erosion. A plurality of bar magnets (20, 22; 108, 110) are arranged in a spaced apart circular array around the cathode chamber with a pole face of each of the magnets tangentially aligned with wall sections (16, 18; 102, 104) of the ionization chamber. The bar magnets thus define a picket fence, wherein the magnetic field between adjacent bar magnets is used to extend the mean path of an electron entering the ionization chamber, improving the probability that it will impact an atom, creating an ion. A grid plate (112) comprises an accelerator grid (204) coated on its inner and outer surfaces with a dielectric coating (206, 208). The inner dielectric coating assumes the potential of the plasma, functioning as a screen grid, while the outer dielectric coating assumes the generally neutral potential of the plasma beam, functioning as a decelerator grid. The dielectric coatings on the accelerator grid protect it from sputtering erosion, and along with the dielectric coating on the interior surface of the ionization chamber provide thermal insulation, thereby improving the operating efficiency of the ion thruster.