Carbon-film field-emission cathodes in a compact orbitron-type ionization vacuum sensor

A possibility to using large-area field-emission cathodes as electron sources in ionic vacuum sensors was investigated. In the specially developed electron-optic scheme, electrons are extracted from a box-shaped cathode by the field of two anode strings. For a large part of the cathode, trajectories of emitted electrons are infinite (in theory), thus high efficiency of gas ionization and overall gauge sensitivity can be achieved. Experimental testing of a sensor prototype has demonstrated general viability of the proposed principle. For a residual gas pressure of about 10(-5) Torr and a cathode emission current 10 nA, the current of collected ions had value of about 1 mu A. The achieved sensitivity is sufficient for some of the possible practical applications of the sensor and can be further improved by simple design corrections. Besides the direct goals of the experiments, they yielded additional information on the performance of carbon emitters in high-voltage devices. Copyright (C) 2007 John Wiley & Sons, Ltd.