Electron source with grid spacer
AssigneeInternational Business Machines Corporation
InventorsJohn Beetson, Andrew Knox
Life of this patent
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Abstract
An electron source having a cathode and a permanent magnet perforated by a plurality of channels extending between opposite poles thereof. The magnet generates, in each channel, a magnetic field which forms electrons received from the cathode into an electron beam for guidance towards a target. An electrode grid is disposed between the cathode and the magnet for controlling flow of electrons from the cathode into each channel. A magnetic field null region of each magnetic field is positioned at a location remote from the electrode grid. Because the null region is positioned remotely from the grid electrodes, flow of electrons can be improved without increasing electrode drive voltage.
Claims43
An electron source comprising:
- a cathode;
- a permanent magnet block perforated by a plurality of channels extending between opposite poles of the magnet block, each channel having an entry side proximate to the cathode and a length which is larger than its width, the magnet block generating, in each channel, a magnetic field which acts upon electrons received from the cathode for a sufficient time to form an electron beam for guidance towards a target;
- grid electrode means disposed between the cathode and the magnet block for controlling flow of electrons from the cathode into each channel;
- and positioning means for positioning a magnetic field null region located at the entry side of each channel to a location remote from the grid electrode means such that the impedance of the electron beams due to the magnetic field null region is lessened.
A method for generating electron beams comprising:
- generating a magnetic field in each of plurality of channels extending between opposite poles of a magnet block, each channel having an entry side proximate to the cathode and a length which is larger than its width, the magnetic field act upon electrons received from the cathode for a sufficient time to form an electron beam for guidance towards a target;
- controlling flow of electrons from the cathode into each channel via grid electrode means disposed between the cathode and the magnet block;
- and positioning a magnetic field null region located at the entry side of each channel to a location remote from the grid electrode means such that the impedance of the electron beams due to the magnetic field null region is lessened.
Dependencies are inferred from the claim text.