Abstract
Efficiently heating a magnetically confined plasma to thermonuclear temperatures remains a central issue in fusion energy research. One well-established technique is to inject beams of neutral particles into the plasma, a process known as neutral beam injection. In the classical picture, fast ions generated from neutral beam injection predominantly heat electrons as they are slowed by friction. This electron heat is then collisionally coupled to the plasma ions, which comprise the fusion fuel. Fast ions can also drive plasma waves, which divert energy from the fuel and can degrade confinement. Here we present new observations from a field reversed configuration plasma in which a beam-driven wave in the open field line region couples directly to fuel ions, drawing a high-energy tail on subcollisional timescales that dramatically enhances the fusion rate. This mode therefore allows the beam energy to bypass the electron channel and does so without having a deleterious effect on global plasma confinement. Our results demonstrate a means of directly and non-destructively coupling energy from fast ions to plasma ions, which may pave the way for improved neutral beam injection heating efficiency or the prevention of ash accumulation with alpha channelling.
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The data that support the plots within this paper and other findings of this study are available from the corresponding author upon reasonable request.
References
Tuszewski, M. Reversed field configurations. Nucl. Fusion 28, 2033–2092 (1988).
Rosenbluth, M. N., Krall, N. A. & Rostoker, N. Finite larmor radius stabilization of ’weakly’ unstable confined plasmas. Nucl. Fusion Suppl. 1, 143–150 (1962).
Binderbauer, M. W. et al. A high performance field-reversed configuration. Phys. Plasmas 22, 056110 (2015).
Binderbauer, M. W. et al. Dynamic formation of a hot field reversed configuration with improved confinement by supersonic merging of two colliding high beta compact toroids. Phys. Rev. Lett. 105, 045003 (2010).
Binderbauer, M. W. et al. Recent breakthroughs on C-2U: Norman’s legacy. AIP Conf. Proc. 1721, 030003 (2016).
Gota, H. et al. Achievement of field-reversed configuration plasma sustainment via 10 mW neutral-beam injection on the C-2U device. Nucl. Fusion 57, 116021 (2017).
Guo, H. Y. et al. Achieving a long-lived high-beta plasma state by energetic beam injection. Nat. Commun. 6, 6897 (2015).
Schmitz, L. et al. Suppressed ion-scale turbulence in a hot high plasma. Nat. Commun. 7, 13860 (2016).
Heidbrink, W. W. Basic physics of Alfvén instabilities driven by energetic particles in toroidally confined plasmas. Phys. Plasmas 15, 055501 (2008).
Belova, E. V. et al. Coupling of neutral-beam-driven compressional Alfvén eigenmodes to kinetic Alfvén waves in NSTX tokamak and energy channeling. Phys. Rev. Lett. 115, 015001 (2015).
Anderson, J. K. et al. Fast ion confinement and stability in a neutral beam injected reversed field pinch. Phys. Plasmas 20, 056102 (2013).
Gates, D. A., Gorelenkov, N. N. & White, R. B. Ion heating by fastparticle-induced Alfvén turbulence. Phys. Rev. Lett. 87, 205003 (2001).
Berk, H., Horton, W., Rosenbluth, M. N. & Rutherford, P. H. Microinstability theory of two-energy-component toroidal systems. Nucl. Fusion 15, 819–844 (1975).
Magee, R. M. et al. Absolute calibration of neutron detectors on the C-2U advanced beam-driven FRC. Rev. Sci. Instrum. 87, 11D815 (2016).
Roche, T. et al. Enhanced magnetic field probe array for improved excluded flux calculations on the C-2U advanced beam-driven field-reversed configuration plasma experiment. Rev. Sci. Instrum. 87, 11D409 (2016).
Beall, M., Deng, B. & Gota, H. Improved density profile measurements in the C-2U advanced beam-driven field-reversed configuration (FRC) plasmas. Rev. Sci. Instrum. 87, 11E128 (2016).
Wesson, J. Tokamaks 3rd edn 246–253 (Clarendon Press, Oxford, 2004).
Deng, B. H. et al. High sensitivity far infrared laser diagnostics for the C-2U advanced beam-driven field-reversed configuration plasmas. Rev. Sci. Instrum. 87, 11E125 (2016).
Clary, R. et al. A mass resolved, high resolution neutral particle analyzer for C-2U. Rev. Sci. Instrum. 87, 11E703 (2016).
Matsuura, H. & Nakao, Y. Distortion of bulk-ion distribution function due to nuclear elastic scattering and its effect on T(d,n)4He reaction rate coefficient in neutral-beam-injected deuterium-tritium plasmas. Phys. Plasmas 14, 054504 (2007).
Arber, T. D. et al. Contemporary particle-in-cell approach to laser-plasma modelling. Plasma Phys. Control Fusion 57, 113001 (2015).
Tajima, T. & Dawson, J. M. Laser electron accelerator. Phys. Rev. Lett. 43, 267 (1979).
Fisch, N. J. The alpha channelling effect. AIP Conf. Proc. 2015, 020001 (2015).
Goorley, T. Initial MCNP6 release overview. Nucl. Technol. 180, 298–315 (2012).
Thompson, M. C. et al. Magnetic diagnostic suite of the C-2 field-reversed configuration experiment confinement vessel. Rev. Sci. Instrum. 83, 10D709 (2012).
Bosch, H.-S. & Hale, G. M. Improved formulas for fusion cross-sections and thermal reactivities. Nucl. Fusion 32, 611–631 (1992).
Zhai, K. et al. The upgrade of the Thomson scattering system for measurement on the C-2/C-2U devices. Rev. Sci. Instrum. 87, 11D602 (2016).
Boris, J. P. Relativistic plasma simulation-optimization of a hybrid code. in Proc. 4th Conference on Numerical Simulation of Plasmas 3–67 (1970).
Esirkepov, T. Zh. Exact charge conservation scheme for particle-in-cell simulation with an arbitrary form-factor.Comput. Phys. Commun. 135, 144–153 (2001).
Yee, K. S. Numerical solution of initial boundary value problems involving Maxwell’s equations in isotropic media. IEEE Trans. Antennas Propag. 14, 302–307 (1966).
Acknowledgements
The authors thank the investors for their support of TAE Technologies and the TAE and Budker teams for their contributions to this project. Special thanks go to E. Granstedt and E. Trask for help with the design of the experiment. This research used resources of the Oak Ridge Leadership Computing Facility, which is a DOE Office of Science User Facility supported under contract no. DE-AC05-00OR22725.
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R.M.M. contributed neutron measurements and neutron calculations, created all the figures and wrote the majority of the text. A.N. ran the PIC simulations, provided output data, and provided text for the ‘Simulation and theory’ section. R.C. provided NPA measurements. S.K. provided neutral beam injection. S.N. provided the analytical theory for benchmarking. T.R. and M.C.T. provided magnetic data. M.W.B. is the driving force behind the C-2U device and helped edited the text. T.T. provided theoretical interpretation of the experimental and simulation data and contributed significantly to the editing of the text.
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TAE Technologies, Inc. is a private corporation owned and financially supported by its shareholders. Some or all of the authors of this manuscript may have a financial interest in the company.
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Magee, R.M., Necas, A., Clary, R. et al. Direct observation of ion acceleration from a beam-driven wave in a magnetic fusion experiment. Nat. Phys. 15, 281–286 (2019). https://doi.org/10.1038/s41567-018-0389-0
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DOI: https://doi.org/10.1038/s41567-018-0389-0
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