Stability of large-area electron-beam diodes

In this letter, we report on experimental measurements of an instability in the large-area electron-beam diodes used to pump krypton–fluoride (KrF) lasers. The instability is identified as the transit-time instability and it is shown that it modulates the electron beam (spatially and temporally), producing a wide spread in the energy and momentum distributions of electrons emerging from the diode. These effects can enhance the energy deposited in the foils and adversely affect the energy-transfer efficiency to the KrF gas. Analysis and simulations of the instability suggest that resistively loaded slots in the cathode should eliminate the instability.