Estimating the reliability of Lawrence Livermore National Laboratory (LLNL) flash X-ray (FXR) machine

Abstract

At Lawrence Livermore National Laboratory (LLNL), our flash X-ray accelerator (FXR) is used on multi-million dollar hydrodynamic experiments.Because of the importance of the radiographs, FXR must be ultrareliable. Flash linear accelerators that can generate a 3 kA beam at 18 MeV are very complex. They have thousands, if not millions, of critical components that could prevent the machine from performing correctly. For the last five years, we have quantified and are tracking component failures. From this data, we have determined that the reliability of the high-voltage gas-switches that initiate the pulses, which drive the accelerator cells, dominates the statistics. The failure mode is a single-switch pre-fire that reduces the energy of the beam and degrades the X-ray spot-size. The unfortunate result is a lower resolution radiograph.FXR is a production machine that allows only a modest number of pulses for testing. Therefore, reliability switch testing that requires thousands of shots is performed on our test stand. Study of representative switches has produced pre-fire statistical information and probability distribution curves. This information is applied to FXR to develop test procedures and determine individual switch reliability using a minimal number of accelerator pulses.

Particle Beam Radiography

“…Efforts to improve FXR beam quality and accelerator reliability have continued [80][81][82][83][84][85][86][87]. They include retuning the LIA to minimize emittance growth [84] and further reducing the temporal variation of the energy, thereby reducing the corkscrew [83,86].…”