Numerical modelization and optimization of flux compression experiments

Summary form only given. The 3.6 MJ energy stored ECF2 pulsed power generator will be on line by mid 2001 for Z-pinch K-shell radiation production at Centre d´Etudes de Gramat. This generator is based on the magnetic flux compression scheme for power amplification from the microsecond to the 100 ns regime. This paper presents the general analytical and numerical method used at CEG to design the flux compression stage. Designing a flux compression stage means many parameters to optimize, ie the masses, initial radii, lengths of both the armature compressing the flux and the pinch, the flux injected in the secondary, the injection gap radius,... 2D MHD codes cannot be used directly to make optimizations on those many parameters due to large CPU time. Fast running advanced OD codes have thus been introduced. They include some models that use physical parameters extracted from 2D MHD simulations. Those models allow to take into account the main processes of the flux compression in order to get reasonable results. They include the diffusion of the magnetic flux through the liner, the development of instabilities in the liner and the losses of flux trapped in the parasitic inductances. Those models are presented. We then show how they compare to the experimental and corresponding 2D MHD results of the flux compression experiments on the Z generator at Sandia National Labs. Finally, we present how those models were used to design the power amplification part of the ECF2 generator.