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Rare Earth Boride Cathode Configuration

IP.com Disclosure Number: IPCOM000076345D
Original Publication Date: 1972-Feb-01
Included in the Prior Art Database: 2005-Feb-24
Document File: 2 page(s) / 28K

Publishing Venue

IBM

Related People

Ahmed, H: AUTHOR [+3]

Abstract

A cathode configuration for a rare earth boride cathode such as a lanthanum hexaboride cathode is shown in Fig. 1, which demonstrates improved heating properties.

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Rare Earth Boride Cathode Configuration

A cathode configuration for a rare earth boride cathode such as a lanthanum hexaboride cathode is shown in Fig. 1, which demonstrates improved heating properties.

In heating a lanthanum hexaboride rod cathode, the power to be dissipated makes it difficult or impossible for the cathode to be used in certain applications such as within a sealed-off evacuated cathode-ray tube envelope. The cathode is heated by the known techniques of radiation heating and electron bombardment by a tungsten coil placed around the rod.

The cathode disclosed is designed such that it is necked down at a point below the bottom turn of the heating coil, in order to reduce thermal conduction down the rod. By necking down the rod, the relative temperatures between the cooler end of the rod and its metal support is low enough to avoid any chemical reaction. Other features of the cathode are, a small supporting structure area reducing conduction and radiation losses and he fact that a more compact eating coil can be used than with previous designs.

Fig. 2 shows a scheme for reducing the operating temperature of heater coils used in the cathode assembly. The drawing shows a cathode assembly including a cathode rod 10, heater coils 12 and a heat shield 14. 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 is supplies just enough current to sustai...