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Melting a Lanthanum Hexaboride Rod Cathode

IP.com Disclosure Number: IPCOM000074254D
Original Publication Date: 1971-Apr-01
Included in the Prior Art Database: 2005-Feb-23
Document File: 2 page(s) / 34K

Publishing Venue

IBM

Related People

Ahmed, H: AUTHOR [+2]

Abstract

This is a method for melting the tip of a sintered lanthanum hexaboride (LaB(6)) cathode to produce a high-density material region for the purpose of shaping fine tips.

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Melting a Lanthanum Hexaboride Rod Cathode

This is a method for melting the tip of a sintered lanthanum hexaboride (LaB(6)) cathode to produce a high-density material region for the purpose of shaping fine tips.

The rod of LaB(6) is mounted in a standard cathode cell assembly. A planar tantalum anode is mounted above the LaB6 cathode. The rod is heated by the normal radiant and electron bombardment method. When the emitting surface reaches a temperature of 1730 degrees C, a 400V pulse is applied to the anode (0.5 sec. to 1 sec. at a repetition rate of one every 2 sec.) The emission current is
0.4 amp giving a total peak power of 160 watts into the anode.

The tantalum anode reaches a temperature close to its melting point in a localized region immediately opposite the cathode. After the application of 10 pulses, the cathode is removed from the system, since the tip of the LaB(6) rod will have melted.

The described method essentially depends on the radiation of power back from the anode to the rod tip. The pulsing of emission prevents a runaway condition which could destroy the anode-cathode assembly.

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