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| Open AccessChorus wave power at the strong diffusion limit overcomes electron losses due to strong diffusion
Strong diffusion limit is the maximum rate of electron loss into the atmosphere from Earth’s radiation belts. Here, the authors show scaling up chorus wave power to the strong diffusion limit causes rapid acceleration of electrons, sufficient to outweigh the losses due to strong diffusion.
- T. A. Daggitt
- , R. B. Horne
- & J. M. Albert
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Article
| Open AccessExperimental study on chorus emission in an artificial magnetosphere
Plasma created in laboratory are useful to understand the properties of atmospheric and space plasma. Here the authors report a laboratory plasma experiment in a dipole magnetic field to show the excitation of chirping whistler waves, i.e. chorus emission.
- Haruhiko Saitoh
- , Masaki Nishiura
- & Zensho Yoshida
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| Open AccessTailoring tokamak error fields to control plasma instabilities and transport
Error fields in tokamak appear due to the imperfections and misalignment of the coils generating magnetic field. Here the authors demonstrate use of error field correction to control the plasma transport and instabilities in a tokamak - KSTAR.
- SeongMoo Yang
- , Jong-Kyu Park
- & Won-Ha Ko
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| Open AccessFirst measurements of p11B fusion in a magnetically confined plasma
The fusion reaction involving proton (p) and boron (11B) has unique advantages over deuterium-tritium (DT) fusion in terms of number of neutrons generated and availability of the fuel components. Here the authors demonstrate the (p,11B) fusion reaction in a magnetically confined plasma at the Large Helical Device.
- R. M. Magee
- , K. Ogawa
- & M. Osakabe
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| Open AccessEquilibrium selection via current sheet relaxation and guide field amplification
Magnetized plasmas display continuous spectra of current-sheet equilibria. How they select a particular equilibrium is not well understood. Now, equilibrium selection in magnetized plasmas is studied by analytical theory, particle-in-cell simulations and spacecraft observations, highlighting the role of current-sheet relaxation processes.
- Young Dae Yoon
- , Deirdre E. Wendel
- & Gunsu S. Yun
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| Open AccessObservation of a new type of self-generated current in magnetized plasmas
Fusion devices like tokamaks require plasma current to generate magnetic field for plasma confinement. Here the authors report an observation of a self-generated anomalous current that contributes up to 30% of the total current in the fusion plasma at KSTAR.
- Yong-Su Na
- , Jaemin Seo
- & Taik Soo Hahm
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| Open AccessEnergy-selective confinement of fusion-born alpha particles during internal relaxations in a tokamak plasma
Confining plasma for fusion requires controlling many parameters. Here the authors report the existence of a narrow parameter space for the simultaneous confinement of energetic alpha particles and removal of slowed-down helium ash in a magnetically confined fusion plasma by using kinetic-magnetohydrodynamic hybrid simulations.
- A. Bierwage
- , K. Shinohara
- & S. Ide
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| Open AccessMulti-scale turbulence simulation suggesting improvement of electron heated plasma confinement
Understanding the transport of the particles and fuel in the fusion plasma is fundamentally important. Here the authors report a cross-link interaction between electron- and ion-scale turbulences in plasma in terms of trapped electron mode and electron temperature gradient modes and their implication to fusion plasma.
- Shinya Maeyama
- , Tomo-Hiko Watanabe
- & Akihiro Ishizawa
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| Open AccessTopological phases and bulk-edge correspondence of magnetized cold plasmas
Magnetized plasma can be regarded as topological matter. Here the authors identify a necessary and sufficient condition for the existence of topological edge mode and find that cold magnetized plasma has ten topological phases in the plasma frequency, cyclotron frequency and wave-vector space.
- Yichen Fu
- & Hong Qin
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| Open AccessCollisionless relaxation of a disequilibrated current sheet and implications for bifurcated structures
Bifurcated current sheets are a recurring feature in magnetized space plasmas. Here the authors explain the emergence of bifurcated structures by natural redistributions of single-particle orbits during the collisionless relaxation process of a disequilibrated current sheet.
- Young Dae Yoon
- , Gunsu S. Yun
- & James L. Burch
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| Open AccessIntegration of full divertor detachment with improved core confinement for tokamak fusion plasmas
Plasma fusion devices like tokamaks are important for energy generation but there are many challenges for their steady state operation. Here, the authors show that full divertor detachment is compatible with high-confinement high-poloidal-beta core plasmas and this prevents the damage to the divertor target plates and the first wall.
- L. Wang
- , H. Q. Wang
- & J. B. Liu
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| Open AccessReal-time feedback control of the impurity emission front in tokamak divertor plasmas
The exhaust of heat and particles is an important challenge in future nuclear fusion devices. Here the authors report the use of carbon emission as indicator for plasma detachment in a tokamak and its real-time feedback control.
- T. Ravensbergen
- , M. van Berkel
- & M. R. de Baar
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| Open AccessEffects of plasma turbulence on the nonlinear evolution of magnetic island in tokamak
Magnetic reconnection and plasma turbulence occur in atmospheric and magnetized laboratory plasmas. Here the authors report evolution of magnetic islands and plasma turbulence in tokamak plasmas using high resolution 2D electron cyclotron emission diagnostics.
- Minjun J. Choi
- , Lāszlo Bardōczi
- & George McKee
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Article
| Open AccessLocal heating of radiation belt electrons to ultra-relativistic energies
Electrons in the Van Allen radiation belts can have energies in excess of 7 MeV, however, the energization mechanism is debated. Here, the authors show phase space density peaks in magnetic coordinate space as a way of analyzing satellite observations which demonstrates that local acceleration is capable of heating electrons up to 7 MeV.
- Hayley J. Allison
- & Yuri Y. Shprits
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| Open AccessOrigin of two-band chorus in the radiation belt of Earth
Chorus waves are crucial on radiation belt dynamics in the space of magnetized planets. Here, the authors show that initially excited single-band chorus waves can quickly accelerate medium energy electrons, and divide the anisotropic electrons into low and high energy components, which subsequently excite two-band chorus waves.
- Jinxing Li
- , Jacob Bortnik
- & Daniel N. Baker
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| Open AccessLoss-cone instability modulation due to a magnetohydrodynamic sausage mode oscillation in the solar corona
Magnetohydrodynamic (MHD) waves and plasma instabilities can be studied during solar flares. Here the authors show evidence for an MHD sausage mode oscillation periodically triggering electron acceleration at a magnetic null point in the solar corona, indicating MHD oscillations in plasma can indirectly lead to loss-cone instability modulation.
- Eoin P. Carley
- , Laura A. Hayes
- & Peter T. Gallagher
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| Open AccessAb initio predictions for polarized deuterium-tritium thermonuclear fusion
Thermonuclear fusion of nuclei of deuterium and tritium may provide the energy for the future and spin polarization is a potential mechanism for enhancing the nuclear reaction. Here the authors predict the enhanced DT fusion rate using chiral effective field theory and ab initio calculations.
- Guillaume Hupin
- , Sofia Quaglioni
- & Petr Navrátil
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| Open AccessThe two-fluid dynamics and energetics of the asymmetric magnetic reconnection in laboratory and space plasmas
Magnetic energy in the plasma is transferred into particle energy by magnetic reconnection. Here the authors show the two-fluid dynamics of asymmetric magnetic reconnection in two different spatial scales of plasma, namely laboratory and astrophysical plasma.
- M. Yamada
- , L.-J. Chen
- & R. Torbert
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| Open AccessEvidence of a turbulent ExB mixing avalanche mechanism of gas breakdown in strongly magnetized systems
Gas breakdown mechanism in plasma under the influence of complex electromagnetic field topology is still debatable. Here the authors present the evidence of the E×B mixing avalanche for gas breakdown in magnetized plasmas in fusion devices as tokamak.
- Min-Gu Yoo
- , Jeongwon Lee
- & Yong-Su Na
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| Open AccessSimulations tackle abrupt massive migrations of energetic beam ions in a tokamak plasma
Understanding the occurrence of sudden changes in plasma parameters is important for the operation of magnetically confined fusion devices. Here the authors use simulation to shed light on the formation of abrupt large-amplitude events and the associated redistribution of energetic ions in a tokamak.
- Andreas Bierwage
- , Kouji Shinohara
- & Masatoshi Yagi
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| Open AccessInference of field reversed configuration topology and dynamics during Alfvenic transients
It is important to understand the fast plasma dynamics in the operation of fusion plasma devices. Here the authors demonstrate the inference on the internal field reversed configuration magnetic topology and their occurrence during fast Alfvenic transient phenomena in C-2U device.
- J. A. Romero
- , S. A. Dettrick
- & Y. Mok
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| Open AccessOscillatory vapour shielding of liquid metal walls in nuclear fusion devices
Vapour shielding is one of the interesting mechanisms for reducing the heat load to plasma facing components in fusion reactors. Here the authors report on the observation of a dynamic equilibrium between the plasma and the divertor liquid Sn surface leading to an overall stable surface temperature.
- G. G. van Eden
- , V. Kvon
- & T. W. Morgan
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| Open AccessSuppressed ion-scale turbulence in a hot high-β plasma
Magnetic fusion reactors with higher ratio of plasma kinetic pressure to magnetic pressure are economically desirable. The authors demonstrate a path to such a reactor in a field reversed configuration that can attain microstability and reduced particle and thermal fluxes by manipulating the shear flow.
- L. Schmitz
- , D. P. Fulton
- & L. C. Steinhauer
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Article
| Open AccessConfirmation of the topology of the Wendelstein 7-X magnetic field to better than 1:100,000
Early stellarator designs suffered from high particle losses, an issue that can be addressed by optimization of the coils. Here the authors measure the magnetic field lines in the Wendelstein 7-X stellarator, confirming that the complicated design of the superconducting coils has been realized successfully.
- T. Sunn Pedersen
- , M. Otte
- & Sandor Zoletnik
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A laboratory study of asymmetric magnetic reconnection in strongly driven plasmas
Magnetic reconnection occurs close to the surface of the sun, in the Earth’s magnetosphere and in astronomical plasmas. Here, the authors investigate magnetic reconnection in a laboratory-based experiments with an asymmetric configuration similar to those found in real astrophysical situations.
- M.J. Rosenberg
- , C.K. Li
- & R.D. Petrasso
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Article
| Open AccessFlow damping due to stochastization of the magnetic field
Understanding the transport of ions, electrons and heat in magnetized plasmas is important to the development of fusion power as well as our understanding of the behaviour of astrophysical objects. Ida et al.find that stochastization of magnetic field lines in a plasma damps plasma flow more strongly than expected.
- K. Ida
- , M. Yoshinuma
- & A. Komori
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Control of magnetohydrodynamic stability by phase space engineering of energetic ions in tokamak plasmas
Tokamak plasmas suffer from magnetohydrodynamic instabilities, driven by gradients in current density or pressure, but techniques to control them are power-hungry and reduce reactor efficiency. Here, an efficient method to control such instabilities using asymmetric ion populations is demonstrated at JET.
- J.P. Graves
- , I.T. Chapman
- & M. Jucker