Pulsed 4-MeV electron injector with an excimer laser driven photocathode

The Relativistic Electron-Beam Experiment injector at the Los Alamos National Laboratory is used to generate a 4-MV pulse across an anode-cathode gap. A simple metal photocathode is illuminated by a pulsed excimer laser. Time-resolved measurements of current, voltage, and current density were made. The resulting quantum efficiencies are being used to obtain the required laser power for a multikiloampere, high-brightness electron gun to be used as an injector for a linear induction accelerator. It is shown that an aluminum photocathode capable of emitting 3.3 kA would require an ArF laser operating at 650 kW/cm². This would generate 72 A/cm², and the laser energy is well below the plasma threshold. To construct a DARHT (Dual Axis Radiographic Hydrotest Facility) injector (3.3 kA, 60 ns), a 1.75-J ArF laser would be required. This type of laser is within current electron-beam-pumped laser technology