Experimental study of Rayleigh Taylor instability by means of magnetic implosion

Abstract

Summary form only given. Russian Federal Institute of Research in Experimental Physics (VNIIEF) and Commissariat l'Energie Atomique (CEA, France) have performed collaboration since 1994 in the area of magnetic implosion. Electrical generators (+Potok type magnetic flux compression generators with fast explosive opening switch) are realized and provided by VNIIEF. CEA provides targets with diagnostics. Rayleigh-Taylor instability analysis in imploding devices is a major question for FCI targets design. Direct use of explosive as a propellant is available, but drawbacks are well known : side effects, high areal masses inducing accuracy limitation in transverse radiographic observation, no simple way for pressure level modulation. These features can be reduced by means of magnetic implosion. This paper describes the result of a joint experiment which was realized in Morovilliers (France),during September 1996. Aluminium liner implosion is used to realize thin hollow tin shell concentration, the shell itself being decelerated by a light foam. Current law in chamber was, as expected, in the range 7-8 MA within a few microseconds. A sinusoidal defect was detected on the inner part of the tin shell. Two X-ray radiographic pictures where realized in the vicinity of shock focalisation time on axis, in order to observe the effects of this perturbation at the interfaces between tin and foam, but also between aluminium liner and magnetic field. Picture quality (contrast, resolution, range) is to be emphasized. Prediction calculations present fine agreement with the data, despite the fact it was a new concept based experiment. This experiment turned to be a useful step to prepare new experiments involving higher value of current (15 MA in chamber) and complex devices.