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Rare Earth Boride Cathode Configuration for Reducing Operating Temperatures

IP.com Disclosure Number: IPCOM000077133D
Original Publication Date: 1972-Jun-01
Included in the Prior Art Database: 2005-Feb-24
Document File: 2 page(s) / 26K

Publishing Venue

IBM

Related People

Blair, WW: AUTHOR [+2]

Abstract

The drawing shows a scheme for reducing the operating temperature of heater coils used in a rare earth boride cathode assembly, such as a lanthanum hexaboride cathode assembly. In the drawing, a cathode assembly including a cathode rod 10, heater coils 12 and a heat shield 14 is shown. The coil 12 is heated by the heater coil supply-voltage source 16 and a bombardment voltage is supplied from source 18. The coil temperature is adjusted so that it supplies just enough current to sustain bombardment. The bombardment coil supply outputs are increased until the cathode rod temperature exceeds a given value, for example 1800 degrees centigrade.

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Rare Earth Boride Cathode Configuration for Reducing Operating Temperatures

The drawing shows a scheme for reducing the operating temperature of heater coils used in a rare earth boride cathode assembly, such as a lanthanum hexaboride cathode assembly. In the drawing, a cathode assembly including a cathode rod 10, heater coils 12 and a heat shield 14 is shown. The coil 12 is heated by the heater coil supply-voltage source 16 and a bombardment voltage is supplied from source 18. The coil temperature is adjusted so that it supplies just enough current to sustain bombardment. The bombardment coil supply outputs are increased until the cathode rod temperature exceeds a given value, for example 1800 degrees centigrade.

The coil current is then reduced, because a condition of self-sustained heating occurs within the heat shield area. The lanthanum hexaboride from cathode rod 10 starts to deposit on coil 12. The temperature of the coil 12 is then further reduced, because of the greater emission from the deposited lanthanum hexaboride. After the deposition of the lanthanum hexaboride on coil 12, the cathode rod 10 is removed and replaced with a sharp-pointed cathode required for high-brightness operation.

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