Electron gun

A 100 kV electron gun with field emission electrode for analytical electron microscopy was improved. A tetrode concept was used to obtain brightness values of 100 million to 1 billion A/sq cm. Using a ceramic insulator, safe control of the accelerating voltage without misdischarges is assured. The basis for routine and automated operation of the gun is provided by the use of integrated electronics at high voltage; safe protection of these modules in the case of discharges; and protective measures for the sensitive field emission tungsten cathode tip. Results show a brightness of three orders of magnitude higher than that of thermal systems.