Bayard-Alpert vacuum gauge with microtips

The Bayard-Alpert ionization gauge is one of the most commonly used gauges for the measurement and control of high and ultrahigh vacua (UHV). The electrons that ionize the residual gas are produced by a hot filament. The replacement of this source by field-effect microtips would overcome many problems caused by thermoionic emission, such as degassing, high power consumption, and mechanical weakness. The results of the experiments involving the replacement of the tungsten filament by an array of microtips fabricated at LETI in a classical Bayard-Alpert gauge are presented. They show that microtips could be a good substitute for filaments in this application, and also they improve some characteristics such as the sensitivity of the gauge and the width of the working scale. Moreover, new options such as fast pulsed operation or fast security cutout modes are possible due to the very short time needed to stabilize the electronic emission. However, an improvement of the tip's material is necessary if the gauge is intended to work continuously at pressures above 10(-5) mbar. (C) 1996 American Vacuum Society.