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Understanding Fuel Magnetization and Mix Using Secondary Nuclear Reactions in Magneto-Inertial Fusion

P. F. Schmit et al.
Phys. Rev. Lett. 113, 155004 – Published 6 October 2014
Physics logo See Viewpoint: Magnetic Fields Lock in the Heat for Fusion

Abstract

Magnetizing the fuel in inertial confinement fusion relaxes ignition requirements by reducing thermal conductivity and changing the physics of burn product confinement. Diagnosing the level of fuel magnetization during burn is critical to understanding target performance in magneto-inertial fusion (MIF) implosions. In pure deuterium fusion plasma, 1.01 MeV tritons are emitted during deuterium-deuterium fusion and can undergo secondary deuterium-tritium reactions before exiting the fuel. Increasing the fuel magnetization elongates the path lengths through the fuel of some of the tritons, enhancing their probability of reaction. Based on this feature, a method to diagnose fuel magnetization using the ratio of overall deuterium-tritium to deuterium-deuterium neutron yields is developed. Analysis of anisotropies in the secondary neutron energy spectra further constrain the measurement. Secondary reactions also are shown to provide an upper bound for the volumetric fuel-pusher mix in MIF. The analysis is applied to recent MIF experiments [M. R. Gomez et al., Phys. Rev. Lett. 113, 155003 (2014)] on the Z Pulsed Power Facility, indicating that significant magnetic confinement of charged burn products was achieved and suggesting a relatively low-mix environment. Both of these are essential features of future ignition-scale MIF designs.

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  • Received 18 June 2014

DOI:https://doi.org/10.1103/PhysRevLett.113.155004

© 2014 American Physical Society

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Magnetic Fields Lock in the Heat for Fusion

Published 14 October 2014

Sandia researchers demonstrate that magnetic fields help retain heat in an imploding pellet of fuel, increasing the number of fusion reactions.

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Vol. 113, Iss. 15 — 10 October 2014

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