MODELING OF A MAGNETIC SENSOR-BASED ON VACUUM FIELD-EMISSION

A model is developed in order to analyse a magnetic sensor based on va cuum field emission. The operation of the sensor is based on the defle ction of the electron current obtained through cold emission due to th e Lorentz force. The electrons' velocities obtained in vacuum are high er than in a semiconductor, being not limited by scattering processes, They allow for higher electron deviations and sensor sensitivities to be obtained. The sensor based on cold emission is less sensitive to e nvironmental conditions (temperature and radiation) compared with semi conductor based sensors, The field emission diode model considered com prises two co-axial metallic cylinders placed in vacuum. The spacing b etween cylinders is d and the diode difference of potential is V-a. Th e inner cylinder acts as emitter. The outer cylinder acts as split-ano de with two active parts of equal angular aperture. The differential s ignal from the two anodes is a function of the applied magnetic field B, which is parallel to the cylinders' axis, The trajectory of the emi tted electrons is obtained both in analytical and numerical form. The sensor relative sensitivity S and magnetic field measuring range B-m a re defined and computed. It is shown that B-m increases linearly with V-a and 1/d, whilst S varies in the opposite way, decreasing with V-a and linearly increasing with d. High sensor relative sensitivities are obtained, in the range several hundred to thousand %/T. These values compare well with experimental data.