Magnetic Direct Drive Magneto-Inertial Fusion Efforts on the Z Machine
Matthew Gomez, Sandia National Laboratories
The Z facility at Sandia National Laboratories consists of the world’s largest pulsed power driver and a multi-kilojoule, terawatt laser. The facility’s mission includes investigating material properties under extreme conditions, high power X-ray sources, and inertial confinement fusion (ICF). In ICF experiments, a target containing fusion fuel is imploded. At stagnation, the fuel reaches the extreme temperatures and pressures required for thermonuclear fusion. In order to relax the ICF stagnation condition requirements, a magnetic field can be introduced. The applied field limits thermal conduction and helps traps fusion products at stagnation.
One technique used to implode ICF targets is Magnetic Direct Drive (MDD), in which a large current (tens of mega-amperes) flows axially through a cylindrical can containing fusion fuel, generating a radially inward force that implodes the cylinder. The pulsed-power drivers used in MDD are relatively efficient and energy-rich but have a longer characteristic timescale, which leads to slower implosion velocities and larger targets. In order to achieve fusion-relevant stagnation conditions at reasonable convergence ratios, the fuel temperature must be heated prior to implosion and a magnetic field is required to insulate the hot fuel from the target’s cold walls. The basic principles of preheated magneto-inertial fusion have been successfully demonstrated on the Z facility, and efforts to increase understanding and performance are ongoing.
*Sandia is a multimission laboratory managed and operated by National Technology and Engineering Solutions of Sandia, LLC., a wholly owned subsidiary of Honeywell International, Inc., for the U.S. Department of Energy’s National Nuclear Security Administration under contract DE-NA0003525.