Staged pinch for controlled thermonuclear fusion

Abstract

Staged pinch implosions provide a means to couple energy to a small-diameter fibre on an extremely fast time scale, circumventing the limitations of conventional pinches. In this scheme the generator current initially traverses an intermediate hollow plasma shell, which compresses onto the fibre placed coaxially and transfers the current to the fibre with a significantly reduced risetime. The results are impressive, since the delivered peak power is increased by several orders of magnitude, the coupling efficiency improves, and the most dangerous plasma instabilities that commonly plague high-density/high-temperature pinches are eliminated. This technique can be fielded on both fast and slow generators (i.e. tens of nanoseconds to microseconds), making it feasible to extend the concept to a wide range of presently assembled systems. Staging may therefore present a dramatically new means of pulsed-energy conversion, which could find many applications. In addressing the requirements for thermonuclear fusion in a staged Z pinch, our preliminary calculations based on zero-D models suggest the potential for a significant thermonuclear burn with generator currents of the order of a few megaamperes and one microsecond risetime. Studies are actively underway at various places around the world (England, France, Germany and Russia) as well as in the USA (UCI/UCR) to investigate different aspects of staged pinching and its applications, particularly those leading to controlled thermonuclear fusion.