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US 5,374,828 AGranted
Electron reversal ionizer for detection of trace species using a spherical cathode
AssigneeThe United States of America as represented by the Administrator of the National Aeronautics and Space Administration
InventorsSaid Boumsellek, Ara Chutjian
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Abstract
A reversal electron, high-current ionizer capable of focusing a beam of electrons to a reversal region employs an indirectly heated cathode having a concave emitting surface of width W<2r, where r is the radius of curvature and preferably a ratio of width to radius approximately equal to one for optimum high current for a given cathode width.
Claims3
In a reversal electron ionizer for trace species detection, a high electron current source comprising
- a spherical cathode for emitting a high current of thermal energy electrons,
- means for electrostatically focusing said thermal energy electrons into a beam along a predetermined axes to a reversal plane,
- and means for electrostatically reversing trajectories of said thermal energy electrons,
- whereby said thermal energy electrons are converted to high current zero-energy electrons at said reversal plane for attachment by trace species of a sample introduced into a region of said reversal plane.
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Dependencies are inferred from the claim text.