Instability of the metal microcrystal surface at intense electron emission*

Some elementary processes are examined, that cause instability of thermal field emission (TFE) current from the thermal field cathode (TFC) tip surface in a strong electric field (Fs≳0.45B/Å). Thermal calculations of TFC apex heating by TFE current have yielded a simple analytical expression for the TFE current limiting density. It is shown that at high TFE current densities (close in the order of magnitude to the limiting value), the TFE current instability is connected with the instability of the TFC emitting surface. The time needed for the field ionization of the desorbing (W) atoms is calculated.