The training method for planar cathode based on carbon fiber powder

The training method for planar cathode based on carbon fiber powder significantly improves the field emission performances. The main point of the training is the forming the optimized emission surface under the residual gases ion bombardment during cathode operating in technical vacuum. There are two main methods of the cathode training. The first one consists in applying of constant voltage between cathode and extracting electrode and other method one should vary the applied voltage to hold the emission current on the constant level according to the cathode structure.