A CONCEPTUAL DESIGN FOR A MICROELECTRONIC IONIZATION VACUUM GAUGE

A novel cold emission microelectronics vacuum gauge is proposed and it s operation is analysed theoretically. The device is based on the cont rolled motion of field emission (FE) electrons in a vacuum working spa ce subject to crossed electric E and magnetic B fields. The arrangemen t is cylindrically symmetrical around the B axis while the radial elec tric field is applied between two coaxial surfaces. The electrons obta ined from a circular FE cathode array placed between these surfaces ar e shown to move on a cycloid-like closed trajectory. Some electrons wi th enough kinetic energy ionize the residual gas molecules. The ions a n collected by an external electrode. The sensitivity of the vacuum ga uge is computed taking into account different cross sections for the i onization process of nitrogen molecules as function of electron kineti c energy and integrating over the electron path. The electron 'time of flight' inside the device is computed assuming an uniform (repelling) electric field in the Z direction. An analysis is performed in order to find the conditions (geometrical and operational) necessary to impr ove the vacuum gauge sensitivity. It is shown that the device should b e operated to allow large electron loops, but at the same time the dev ice dimensions should he large enough to allow the electron to acquire enough kinetic energy for an efficient ionization process to take pla ce. (C) 1998 Elsevier Science B.V.