Tail-ion transport and Knudsen layer formation in the presence of magnetic fields

Journal Article · Fri Nov 15 00:00:00 EST 2013 · Physics of Plasmas

DOI:https://doi.org/10.1063/1.4831958· OSTI ID:22218434

Schmit, P. F. ^[1]; Molvig, Kim; Nakhleh, C. W. ^[2]

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1. Sandia National Laboratories, MS 1186, P.O. Box 5800, Albuquerque, New Mexico 87185-1186 (United States)
2. Los Alamos National Laboratory, MS B259, P.O. Box 1663, Los Alamos, New Mexico 87545 (United States)

Knudsen layer losses of tail fuel ions could reduce significantly the fusion reactivity of highly compressed cylindrical and spherical targets in inertial confinement fusion (ICF). With the class of magnetized ICF targets in mind, the effect of embedded magnetic fields on Knudsen layer formation is investigated for the first time. The modified energy scaling of ion diffusivity in magnetized hot spots is found to suppress the preferential losses of tail-ions perpendicular to the magnetic field lines to a degree that the tail distribution can be at least partially, if not fully, restored. Two simple threshold conditions are identified leading to the restoration of fusion reactivity in magnetized hot spots. A kinetic equation for tail-ion transport in the presence of a magnetic field is derived, and solutions to the equation are obtained numerically in simulations. Numerical results confirm the validity of the threshold conditions for restored reactivity and identify two different asymptotic regimes of the fusion fuel. While Knudsen layer formation is shown to be suppressed entirely in strongly magnetized cylindrical hot spot cavities, uniformly magnetized spherical cavities demonstrate remnant, albeit reduced, levels of tail-ion depletion.

• OSTI ID: 22218434
• Journal Information: Physics of Plasmas, Vol. 20, Issue 11; Other Information: (c) 2013 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA); ISSN 1070-664X
• Country of Publication: United States
• Language: English

Related Subjects

70 PLASMA PHYSICS AND FUSION TECHNOLOGY
ASYMPTOTIC SOLUTIONS
BOUNDARY LAYERS
CYLINDRICAL CONFIGURATION
ELECTRON BEAM TARGETS
ICF DEVICES
INERTIAL CONFINEMENT
ION BEAM TARGETS
KINETIC EQUATIONS
KNUDSEN FLOW
LASER TARGETS
MAGNETIC FIELDS
MAGNETOHYDRODYNAMICS
NUMERICAL ANALYSIS
PLASMA
PLASMA SIMULATION
SPHERICAL CONFIGURATION
TAIL IONS
THERMONUCLEAR FUELS
THERMONUCLEAR REACTORS