Electron motion and confinement in the orbitip vacuum gauge II. Modelling results

The sensitivity of the "orbitip" ionization vacuum gauge has been studied, by modelling the electron motion and confinement inside the device. The orb itip has two electrodes shaped as coaxial cylinders, and the electrons are provided by a field emission array, Numerical solutions of the electron equ ations of motion are used to study the device sensitivity. The electrons ha ve irregular helical trajectories greatly increasing their mean path and th erefore the gauge sensitivity. It is shown that the device sensitivity is m aximal when conditions are fulfilled to achieve a circular helical electron trajectory. Accordingly, a gauge design procedure is outlined. Under such conditions, the study predicts extremely high values of the gauge sensitivi ty, in the range of 10(2)-10(3) Torr(-1). (C) 1999 Elsevier Science B.V. Al l rights reserved.