[Summary] [Franšais][English]

Abstract

In order to study the feasibility of creating an intense X ray source for France, the Centre d'╔tudes de Gramat (CEG ) is investigating several technologies. The Syrinx project is looking at the potential of High Pulse Power technologies for Isentropic Compression Experiments, High Temperatures Hohlraums and Radiation Hardening (X rays between $1$ and $10 \, \mathrm{keV}$).

The load used for the radiation production is a Z-pinch, that is to say a plasma cylinder imploded by an electrical current, which converts energy from the electrical generator into internal energy and then into radiative power. An optimum is reached for a high electrical current supplied in a short time.

So it is necessary to provide a power amplification stage allowing electrical currents of the order of $10 \, \mathrm{MA}$ with a hundred nanoseconds rise time to be delivered to the load. Usually, generators use pulse forming lines or plasma opening switches.

Magnetic Flux Compression, another power amplification possibility, is studied in this dissertation. It has enabled the compression of the $100 \, \mathrm{ns}$ pulse of the Z machine (Sandia National Laboratories) into a $40 \, \mathrm{ns}$ pulse and the compression of the $1 \, \mathrm{\mu s}$ pulse of the ECF generator (CEG ) into a $100 \, \mathrm{ns}$ pulse. The design of the flux compressor has to take into account the generator supplying the current and the kind of load receiving the amplified current.

This technology has the advantage of a characteristic implosion time less than a micro second avoiding many of the problems the explosive driven flux compression ran into.

This research work consisted initially in finding the right parameters for several codes (circuits codes, plasma codes ...) in order to adapt them to the Flux Compression. These numerical tools have then been used to design experiments on Z and ECF . These experiments have reached $5 \, \mathrm{Mbar}$ with shock and more than $2 \, \mathrm{Mbar}$ in isentropic compression as well as $110 \, \mathrm{eV}$ in a hohlraum. Insights gleaned from the interpretation of the shots have been compared to our understanding of the power amplification system and of the loads. Finally, this allows us to improve our numerical tools and to optimize the Flux Compression concept.

The work which has been done should lead to the extrapolation of the concept to an X ray generator of the $60 \, \mathrm{MA}$ class.

Mathias.Bavay_at_ingenieurs-supelec.org - juillet 2002