Modeling of a miniaturized mass spectrometer with field emission electron source

A miniaturized mass spectrometer with field emission electron source is proposed and its operation is theoretically analyzed. The mass spectrometer has overall dimensions in the centimeter range, making it portable and suitable for integration in new systems. The electrons are obtained from a linear array of gated cathode emitters placed on a cylinder parallel with its symmetry axis. The ions are locally obtained near the cathode when the electrons hit the gas molecules. A radial electric field is applied between the inner cylinder and an outer cylinder coaxial with the first one. A magnetic field is applied along the device symmetry axis. The ions are deflected in this combination of crossed electric and magnetic fields, being collected by electrodes placed on the external cylindrical surface. Different ions are deflected in different ways, according to their mass. Accordingly, they are collected at different locations, allowing for their identification. A combined numericalranalytical method is used to analyze the ion trajectories. The sensitivity of the device has been defined and modeled. Factors affecting the operation of the device have been investigated. q1999 Elsevier Science B.V. All rights reserved.