Understanding and Exploiting Transport in Magneto-Inertial Fusion Plasmas

Ian Ochs, Princeton University

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Achieving economical fusion requires achieving the Lawson criterion, a triple-product of density, temperature and energy confinement time. Fusion energy has historically been dominated by two approaches to achieving this triple product: magnetic fusion, which aims to confine a low-density plasma for a long time via magnetic fields; and inertial fusion, which aims to implode a hot plasma to huge densities just long enough to burn the fusion fuel. Magneto-inertial fusion schemes such as MagLIF and magnetized hohlraum aim to combine the best parts of each approach, embedding a magnetic field in the imploding field to limit the particle and heat transport across the plasma, thus decreasing the required density and temperature for economical fusion. Although most theoretical work on magneto-inertial fusion has focused on electron dynamics, a sufficiently strong magnetic field also changes the ion transport dynamics. In an initial study1, we show how magnetized ion transport effects tend to naturally draw fuel into the fusion hotspot while flushing ash and impurities outward. This flushing is a free effect of the design that can increase the fusion yield substantially in reactions with significant burnup. This motivated the development of a code, MITNS2, to further explore these magnetized effects, helping reveal new and useful differential heating effects in the presence of rotation, which has been predicted near the MagLIF hotspot3. The methods and code used are also suitable for the study of other rotating plasma systems, such as centrifuges for nuclear waste filtration4. 1I. E. Ochs and N. J. Fisch, Favorable Collisional Demixing of Ash and Fuel in Magnetized Inertial Fusion, Physical Review Letters 121, 235002 (December, 2018). 2E. J. Kolmes*, I. E. Ochs*, and N. J. Fisch, MITNS: Multiple-Ion Transport Numerical Solver, Submitted to Computer Physics Communications (2020). 3M. E. Mlodik, E. J. Kolmes, I. E. Ochs, and N. J. Fisch, Heat Pump via Charge Incompressibility in a Collisional Magnetized Multi-Ion Plasma, submitted to Physical Review E (2020). 4I. E. Ochs, R. Gueroult, N. J. Fisch, and S. J. Zweben, Collisional considerations in axial-collection plasma mass filters, Physics of Plasmas 24, 043503 (April, 2017).

Abstract Author(s): Ian Ochs