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Title: Theory of ignition and burn propagation in inertial fusion implosions

Journal Article · · Physics of Plasmas
DOI:https://doi.org/10.1063/1.5143889· OSTI ID:1631033

A detailed analytic model is presented here to investigate the physics of burn propagation in inertially confined plasmas. The onset of ignition and burn propagation occurs when alpha heating of the hot spot causes rapid ablation of shell mass into the hot spot. This allows large energy gains to be achieved since most of the fuel mass is located in the shell. Here, we first present a comprehensive review of previous analytic models that have been used to describe the physics of hot-spot evolution and ignition; we then show that a proper description of a propagating burn wave requires a comprehensive model of hot spot and shell evolution that includes proper mass conservation in the shell, fusion reactivity, and fuel depletion. The analytic theory is in good agreement with detailed radiation-hydrodynamic simulations that predict the onset of burn propagation as occurring when the yield enhancement caused by alpha heating is between 15- and 25-fold, $$f_α$$ ~ 1.4, where $$f_α$$ = alpha energy deposited/hot-spot energy at bang time, and the hot-spot burnup fraction is approximately 2%. We show that the definition of ignition is not sensitive to the alpha-particle stopping power nor asymmetries provided that the absorbed fraction of alpha particles $$θ_α$$ is correctly accounted for. Finally, we use the results of 2-D simulations to show that even when $$θ_α$$ is small and unknown (as is true in hot spots with mid modes that have significant leakage of alpha particles into the surrounding cold bubbles), one can still relate the experimentally measureable parameter $$\chi^{53}_α$$ to the yield amplification and the burning-plasma parameter $$Q^{\text{hs}}_α$$ = alpha energy deposited/total input work delivered to the hot spot

Research Organization:
Univ. of Rochester, NY (United States). Lab. for Laser Energetics
Sponsoring Organization:
USDOE National Nuclear Security Administration (NNSA); New York State Energy Research and Development Authority
Grant/Contract Number:
NA0003856
OSTI ID:
1631033
Alternate ID(s):
OSTI ID: 1630376
Report Number(s):
2019-287; 2522; 1566; 2019-287, 2522, 1566; TRN: US2200731
Journal Information:
Physics of Plasmas, Vol. 27, Issue 5; ISSN 1070-664X
Publisher:
American Institute of Physics (AIP)Copyright Statement
Country of Publication:
United States
Language:
English
Citation Metrics:
Cited by: 18 works
Citation information provided by
Web of Science

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