Vacuum Steered-Electron Electric-Field Sensor

In a new type of microelectromechanical system (MEMS) electric-field sensor, a sheet of electrons is thermionically emitted by a hot cathode, flows through a vacuum, and is collected by a pair of anodes 2000 μm away. As the electrons move through the vacuum, they are steered by external electric fields, resulting in a differential current at the anodes. The micromachined tungsten cathode has a low-work-function coating and is suspended over a cavity on a glass chip. These sensors have been operated both in a vacuum chamber and sealed in glass vacuum tubes. Measured sensitivities in a vacuum tube at 10,100, and 1000 Hz are 470, 230, and 140 mV/m·Hz^1/2, respectively; sensitivities in a vacuum chamber at the same frequencies are 34, 6.3, and 2.4 mV/m·Hz^1/2, respectively.