Cylindrically convergent implosions of metal liners for quasi-isentropic compression of deuterium

• Main Author: Weinwurm, Marcus
• Other Authors: Chittenden, Jeremy
• Published: Imperial College London 2014
• Subjects: 530
• Online Access: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.650702

To date our understanding of strongly coupled, degenerate plasmas is incomplete. In particular considerable disagreement exists between theories of hydrogenic matter (HM) at pressures greater than 100 gigapascals (GPa) and temperatures below 3 electronvolts (eV). The predicted transition of fluid molecular hydrogen to a metallic atomic liquid has large implications for models of the interior structure and evolution of gas giants. Experimental confirmation of this transition is still pending. Furthermore, the properties of deuterium-tritium in this regime are of great interest to inertial confinement fusion. In this thesis we propose a scheme that can create strongly coupled, degenerate hydrogenic plasmas at terapascal (TPa) pressures on pulsed power machines. Our results show that this can be achieved by initiating cylindrically converging isentropic flow of sample material inside a metal liner. The liner acts as a pusher that drives a predefined compression of the fill, which is obtained by constructing an asymptotically self-similar implosion of cryogenically condensed HM. An empirical model that gives the required pulse shape for recreating this implosion inside the liner is introduced. Results of magnetohydrodynamic simulations demonstrate that a peak current of 10.8 megaamperes (MA) is sufficient for assembling nearly uniform HM at a stagnation pressure of 13 TPa and at temperatures of approximately 1.5 eV. A study of the stability of the implosion to imperfections of the liner's surface finds that liner-driven isentropic compression of hydrogen is robust to magneto-Rayleigh-Taylor growth for sufficiently thick liners. Since the methods in this work are readily adapted to a range of materials, an experimental realization could significantly extend our knowledge of degenerate, strongly coupled plasmas in general. Finally, we broaden our focus to the compression of the metal liner itself. Potential advantages of reducing shock heating and thereby increasing the degeneracy of liner material during a magnetized liner inertial fusion implosion are discussed.