Electrons motion and confinement in the orbitip vacuum gauge I. Theory

Electron motion and confinement inside the "orbitip" ionization vacuum gaug e have been studied. The orbitip has two electrodes shaped as coaxial cylin ders, and the electrons are injected by a field emission array. Generally, the electrons have helical trajectories with complicated shapes. Electron c onfinement conditions are studied and several design hints are outlined. It is shown that electron confinement at the device end can be obtained by a small narrowing of the outer electrode. The longest electron trajectories a re circular helical ones, with large radius and small helix increment. Thes e optimal trajectories also assure minimal trajectory fluctuations for the electron population. (C) 1999 Elsevier Science B.V. All rights reserved.