Method and arrangement for preventing cathode damage when switching on field emission electron guns

摘要

The invention is directed to a method of preventing cathode damage when switching on an electron gun having a field emission cathode assembly including a cathode, a first electrode and a ground electrode. During normal operation of the electron gun, an extraction voltage is applied across the cathode and the first electrode and an accelerating voltage is applied across the cathode and the ground electrode. A direct galvanic connection is established between the cathode and the first electrode prior to normal operation of the electron gun. During a burn-in period, only the accelerating voltage is applied. This accelerating voltage may include an overvoltage of up to twenty percent. Then the galvanic connection between the cathode and the first electrode is interrupted and the extraction voltage is applied. An arrangement for carrying out the invention is also disclosed.