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Extended-MHD simulations of power flow along a pulsed-power transmission line are performed in a 2-D axisymmetric geometry, in particular looking at the influence of Hall physics for a transmission line coupled to the liner used in a magnetized liner inertial fusion experiment at Sandia National Labs. It was recently shown by the authors that, for a coaxial transmission line, when Hall physics is included, significantly more blow-off occurs from plasma initialized against the anode compared to the cathode. The mechanism of this blow-off was traced to electron ${\text{E}}\times {\text{B}}$ drift modeled by the Hall term. This result is also observed for the present simulations, and it is shown that the anode blow-off significantly delays the coupling of current to the liner. It is also found that Hall MHD and MHD results are sensitive to the treatment of density floors and the plasma–vacuum interface. Although MHD shows more sensitivity than Hall MHD, correct modeling of the transition from plasma to vacuum remains an unsolved problem that must be addressed in order to improve the predictive capability of fluid-based power flow simulations with regard to energy coupling.

Magnetized Liner Inertial Fusion (MagLIF) is a magneto-inertial fusion concept, which is presently being studied on the Z Pulsed Power Facility. The concept utilizes an axial magnetic field and laser heating to produce fusion-relevant conditions at stagnation despite a peak magnetically driven implosion velocity of less than 100 km/s. Initial mymargin experiments demonstrated the viability of the concept but left open questions about the amount of laser energy coupled to the fuel and the role that mix played in the stagnation conditions. In this paper, simple methodologies for estimating the laser energy coupled to the fuel and determining the stagnation pressure and mix are presented. These tools enabled comparisons across many experiments to establish performance trends, as well as allow comparisons with 2-D magnetohydrodynamics simulations. The initial experiments were affected by low laser energy coupling (0.2–0.6 kJ), which resulted in reduced neutron yields (1– $2\times 10^{12}$ ). In addition, all early experiments utilized mid-Z (aluminum) fuel-facing components. Mixing from these components had a significant impact on stagnation and increased with laser energy. Lower neutron yields (1– $3\times 10^{11}$ ) were measured with higher laser coupling (0.8–1.2 kJ), which significantly deviated from the predicted scaling. When all fuel-facing components were made from a low-Z material (beryllium), neutron production increased ( $3.2\times 10^{12}$ ) and scaled as expected with laser energy; experimental yields were approximately 40% of simulated yields. In addition, roughly I4 yield scaling was observed in experiments, where the load current was varied from 16–18 MA. These results represent the first step in experimental demonstration of stagnation performance scaling with input parameters in MagLIF.

High current pulsed-power generators efficiently store and deliver magnetic energy to z-pinch targets. We review applications of magnetically driven implosions (MDIs) to inertial confinement fusion. Previous research on MDIs of wire-array z-pinches for radiation-driven indirect-drive target designs is summarized. Indirect-drive designs are compared with new targets that are imploded by direct application of magnetic pressure produced by the pulsed-power current pulse. We describe target design elements such as larger absorbed energy, magnetized and pre-heated fuel, and cryogenic fuel layers that may relax fusion requirements. These elements are embodied in the magnetized liner inertial fusion (MagLIF) concept [Slutz “Pulsed-power-driven cylindrical liner implosions of laser pre-heated fuel magnetized with an axial field,” Phys. Plasmas, 17, 056303 (2010), and Stephen A. Slutz and Roger A. Vesey, “High-Gain Magnetized Inertial Fusion,” Phys. Rev. Lett., 108, 025003 (2012)]. MagLIF is in the class of magneto-inertial fusion targets. In MagLIF, the large drive currents produce an azimuthal magnetic field that compresses cylindrical liners containing pre-heated and axially pre-magnetized fusion fuel. Scientific breakeven may be achievable on the Z facility with this concept. Simulations of MagLIF with deuterium-tritium fuel indicate that the fusion energy yield can exceed the energy invested in heating the fuel at a peak drive current of about 27 MA. Scientific breakeven does not require alpha particle self-heating and is therefore not equivalent to ignition. Capabilities to perform these experiments will be developed on Z starting in 2013. These simulations and predictions must be validated against a series of experiments over the next five years. Near-term experiments are planned at drive currents of 16 MA with D2 fuel. MagLIF increases the efficiency of coupling energy (=target absorbed energy/driver stored energy) to targets by 10-150X relative to indirect-drive targets. MagLIF also increases the absolute energy absorbed by the target by 10-50X relative to indirect-drive targets. These increases could lead to higher fusion gains and yields. Single-shot high yields are of great utility to national security missions. Higher efficiency and higher gains may also translate into more compelling (lower cost and complexity) fusion reactor designs. We will discuss the broad goals of the emerging research on the MagLIF concept and identify some of the challenges. We will also summarize advances in pulsed-power technology and pulsed-power driver architectures that double the efficiency of the driver.