Publications

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The MagLIF (Magnetized Liner Inertial Fusion) concept [Slutz et al., Phys. Plasmas 17, 056303 (2010)] has demonstrated fusion-relevant plasma conditions [Gomez et al., Phys. Rev. Lett. 113, 155003 (2014)] on the Z accelerator using external field coils to magnetize the fuel before compression. We present a novel concept (AutoMag), which uses a composite liner with helical conduction paths separated by insulating material to provide fuel magnetization from the early part of the drive current, which by design rises slowly enough to avoid electrical breakdown of the insulators. Once the magnetization field is established, the drive current rises more quickly, which causes the insulators to break down allowing the drive current to follow an axial path and implode the liner in the conventional z-pinch manner. There are two important advantages to AutoMag over external field coils for the operation of MagLIF. Low inductance magnetically insulated power feeds can be used to increase the drive current, and AutoMag does not interfere with diagnostic access. Also, AutoMag enables a pathway to energy applications for MagLIF, since expensive field coils will not be damaged each shot. Finally, it should be possible to generate Field Reversed Configurations (FRC) by using both external field coils and AutoMag in opposite polarities. This would provide a means to studying FRC liner implosions on the 100 ns time scale.

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Magneti zed Liner Inerti al Fusion (MagLIF ) is an inertial confinement fusion (ICF) concept that includes a strong magnetic field embedded in the fuel to mitigate thermal conduction loss during the implosion . MagLIF experiments on Sandia's 20 MA Z Machine uses an external Helmholtz - like coil pair for fuel premagnetization . By contrast, t he novel AutoMag concept employs a composite liner (cylindrical tube) with helically oriented conduction paths separated by insulating material to provide axial premagnetization of the fuel . Initially, during a current prepulse that slowly rises to %7E1 MA, current flows helically through the AutoMag liner , and so urces the fuel with an axial field . Next, a rapidly rising main current pulse breaks down the insulation and current in th e liner becomes purely axial. The liner and premagnetized fuel are then compressed by the rapidly growing azimuthal field external to t he liner. This integrated axial - field - production mechanism offers a few potential advantages when compared to the externa l premagnetization coils. AutoMag can increase drive current to MagLIF experiments by enabling a lower inductance transmission line , provide higher premagnetization field (>30 T), and greatly increase radial x - ray diagnostic access. 3D electromagnetic si mulations using ANSYS Maxwell have been completed in order to explore the current distributions within the helical conduction paths, the inter - wire dielectric strength properties, and the thermal properties of the helical conduction paths during premagneti zation (%7E1 MA in 100ns). Th ree liner designs , of varying peak field strength, and associated varying risk of dielectric breakdown, will soon be tested in experiments on the %7E 1 MA, 100ns Mykonos facility. Experiments will measure B z (t) inside of the line r and assess failure mechanisms.

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