Multi-kiloampere, electron-beam generation using metal photo-cathodes driven by ArF and KrF lasers

An electron-beam-pumped laser operating at ArF (193 nm) or KrF (248 nm) producing 35 MW (3.5 J in 100 ns) has been used to illuminate a micro-machined aluminum cathode. The cathode was pulsed to 2.75 MY at fields of 185 kV/cm (I5-cm AK gap) using REX [1,2] (a 4-MV, 5-kA, 85-ns) pulsed-diode machine. The extracted current versus incident laser power (the quantum efficiency) was measured for KrF at 5×10⁻⁵ and for ArF which was significantly higher at 1×10⁻³. Current densities of 100 A/cm² and total currents of 2 kA have been achieved, the latter by increasing the cathode area in proportion to the laser power.