Abstract :
The FXR machine is a nominal 4 kA, 20 MeV, linear induction, electron accelerator for flash radiography at LLNL. The machine met its baseline requirements in March 1982. Since then, the performance has been greatly improved. We have achieved stable and repeatable beam acceleration and transport, with over 80% transmission to the tungsten bremsstrahlung target located some 35 m downstream. For best stability, external beam steering has been eliminated almost entirely. We regularly produce over 500 Roentgen at 1 m from the target (TLD measurement), with a radiographic spot size of 3-5 mm. Present efforts are directed towards the development of a 4 kA tune, working interactively with particle-field and beam transport code models. A remaining uncertainty is the possible onset of RF instabilities at the higher current levels.
