0D numerical modelisation and optimization of flux compression experiments

The 3.6 MJ energy stored ECF2 pulsed power generator will be on line by the fall of 2001 for Z-pinch K-shell radiation production at Centre d´Etudes de Gramat (CEG). This generator is based on the magnetic flux compression scheme for power amplification from the microsecond to the 100 ns regime. Also, some experiments have been performed at Sandia National Laboratories (SNL) on Z to demonstrate the interest of this scheme. This paper presents a general numerical method to design the flux compression stage for which many parameters need to be optimized : the masses, initial radii, lengths of both the armature compressing the flux and the pinch, the flux injected in the secondary, and 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 improved OD codes have thus been developed. They include some models that use physical parameters extracted from 2D MHD simulations. Those models 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 and the losses of flux trapped in the parasitic inductances (diffusion in the liner, instabilities). Those models are presented. We then compare the obtained results to the experimental data to the 2D MHD simulations of the flux compression experiments on the Z generator at Sandia National Laboratories. Finally, we present how those 0D codes are used optimize the parameters for isentropic compression experiments.