Monday, May 29, 2006

US Patent 7049823 - Electron Emitting Nanotubes Used In Pressure Gauge

In an earlier post I mentioned how reissue patent RE 38561, which contains the basic claims to electron emitting nanotubes, may be the most valuable nanotech patent issued because of the large number of emerging commercial applications of this use of electron emitting nanotubes in flat panel displays, electron microscopy, lithography, microwave amplifiers, etc.
US 7049823 provides an example of yet another new field of application for electron emitting nanotubes - a vacuum gauge. Claim 1 reads -

1. An ionisation vacuum gauge for measuring the residual pressure of a gaseous material in a container (10) comprising: an electron-emitting cathode (31), said cathode is formed by a plurality of nanotubes, distributed over a surface of said cathode, a grid (13; 33; 133; 133') for accelerating the electrons emitted by said cathode, a plate (15; 35) for collecting the ionised positive molecules of said gaseous material, said plate (35) disposed outside of said accelerating grid (33:133;133') and a galvanometer (21) connected to said plate for measuring the plate current to determine the value of the residual pressure inside the container.

Ionisation vacuum gauges are actually fairly commonly used to enable low pressure lithography and microscopy environments. The use of nanotubes as an electron emitter in these devices provides advantages of lower power consumption, a high degree of directional control of the electron beam, and miniaturization.