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  • Non-planar coil winding angle optimization for compatibility with non-insulated high-temperature superconducting magnets
    J. Plasma Phys. (IF 2.238) Pub Date : 2020-10-20
    C. Paz-Soldan

    The rapidly emerging technology of high-temperature superconductors (HTS) opens new opportunities for the development of non-planar non-insulated HTS magnets. This type of HTS magnet offers attractive features via its simplicity and robustness, and is well suited for modest size steady-state applications such as a mid-scale stellarator. In non-planar coil applications the HTS tape may be subject to

    更新日期:2020-10-20
  • Non-resonant acceleration of charged particles driven by the associated effects of the radiation reaction
    J. Plasma Phys. (IF 2.238) Pub Date : 2020-10-20
    F. Russman; I. Almansa; E. Peter; S. Marini; F. B. Rizzato

    In the present analysis, we study effects of the radiation reaction (RR) on the dynamics of charged particles submitted to the action of localized longitudinal high-frequency carriers travelling at the speed of light. As the wave's crests and troughs keep overtaking particles, dissipative RR forces tend to drag particles alongside the wave in an effort to reduce the relative wave–particle speed. Particles

    更新日期:2020-10-20
  • Stability of a tokamak plasma with diffuse toroidal rotation
    J. Plasma Phys. (IF 2.238) Pub Date : 2020-10-20
    O. E. López; L. Guazzotto

    The present work considers the stability of a high- $\beta$ , large aspect ratio, circular plasma with diffuse profiles for the safety factor and the angular toroidal frequency (López & Guazzotto, Phys. Plasmas, vol. 24, 032501). An application of the Frieman–Rotenberg formalism results in a system of scalar eigenmode equations whose coupling is retained at the plasma–vacuum transition but is disregarded

    更新日期:2020-10-20
  • Spatial distributions of plasma parameters in conventional magnetron discharges in presence of nanoparticles
    J. Plasma Phys. (IF 2.238) Pub Date : 2020-10-16
    A. Chami; C. Arnas

    Two-dimensional spatial measurements of magnetic field and plasma parameters have been performed in conventional magnetron DC discharges during the formation of metallic nanoparticles. Correlations between the electron density and temperature distributions, and the magnetic field geometry and strength have been established. A sharp increase of the plasma potential is found on the edge of the last magnetic

    更新日期:2020-10-17
  • Magnetic well and Mercier stability of stellarators near the magnetic axis
    J. Plasma Phys. (IF 2.238) Pub Date : 2020-10-15
    Matt Landreman; Rogerio Jorge

    We have recently demonstrated that by expanding in small distance from the magnetic axis compared with the major radius, stellarator shapes with low neoclassical transport can be generated efficiently. To extend the utility of this new design approach, here we evaluate measures of magnetohydrodynamic interchange stability within the same expansion. In particular, we evaluate the magnetic well, Mercier's

    更新日期:2020-10-16
  • Elasticity of tangled magnetic fields
    J. Plasma Phys. (IF 2.238) Pub Date : 2020-10-15
    D. N. Hosking; A. A. Schekochihin; S. A. Balbus

    The fundamental difference between incompressible ideal magnetohydrodynamics and the dynamics of a non-conducting fluid is that magnetic fields exert a tension force that opposes their bending; magnetic fields behave like elastic strings threading the fluid. It is natural, therefore, to expect that a magnetic field tangled at small length scales should resist a large-scale shear in an elastic way,

    更新日期:2020-10-16
  • Introduction of Zeeman splitting in CHIANTI
    J. Plasma Phys. (IF 2.238) Pub Date : 2020-10-09
    M. Giarrusso; E. Landi; G. Del Zanna; F. Leone

    High-resolution spectra emitted by laboratory plasmas provide invaluable diagnostic tools for the measurement of plasma properties. To be implemented, they require a large amount of atomic data and transition rates, which are available in several spectral codes. In this paper we present a new feature added to the CHIANTI code, which allows us to calculate the Zeeman splitting of spectral lines in the

    更新日期:2020-10-11
  • Magnetic energy dissipation during the current quench of disruption in EAST
    J. Plasma Phys. (IF 2.238) Pub Date : 2020-10-08
    T. Tang; L. Zeng; D. L. Chen; R. S. Granetz; S. T. Mao; Y. M. Duan; L. Zhang; H. D. Zhuang; X. Zhu; H. Q. Liu; B. Shen; Y. X. Jie; X. Gao

    A disruption database characterizing the current quench of disruptions with ITER-like tungsten divertor has been developed on EAST. It provides a large number of plasma parameters describing the predisruptive plasma, current quench time, eddy current, and mitigation by massive impurity injection, which shows that the current quench time strongly depends on magnetic energy and post-disruption electron

    更新日期:2020-10-08
  • Comparative study of the surface potential of magnetic and non-magnetic spherical objects in a magnetized radio-frequency discharge
    J. Plasma Phys. (IF 2.238) Pub Date : 2020-10-05
    Mangilal Choudhary; Roman Bergert; Slobodan Mitic; Markus H. Thoma

    We report measurements of the time-averaged surface floating potential of magnetic and non-magnetic spherical probes (or large dust particles) immersed in a magnetized capacitively coupled discharge. In this study, the size of the spherical probes is taken greater than the Debye length. The surface potential of a spherical probe first increases, i.e. becomes more negative at low magnetic field ( $B

    更新日期:2020-10-05
  • Advancing the physics basis for quasi-helically symmetric stellarators
    J. Plasma Phys. (IF 2.238) Pub Date : 2020-10-01
    A. Bader; B. J. Faber; J. C. Schmitt; D. T. Anderson; M. Drevlak; J. M. Duff; H. Frerichs; C. C. Hegna; T. G. Kruger; M. Landreman; I. J. McKinney; L. Singh; J. M. Schroeder; P. W. Terry; A. S. Ware

    A new optimized quasi-helically symmetric configuration is described that has the desirable properties of improved energetic particle confinement, reduced turbulent transport by three-dimensional shaping and non-resonant divertor capabilities. The configuration presented in this paper is explicitly optimized for quasi-helical symmetry, energetic particle confinement, neoclassical confinement and stability

    更新日期:2020-10-02
  • Implementation of fictitious absorbing layers with deceleration effects for one-dimensional Schrödinger equations
    J. Plasma Phys. (IF 2.238) Pub Date : 2020-10-01
    Hitoshi Kanai; Tomo Tatsuno

    Absorbing boundary conditions or layers are used in simulations to reduce or eliminate wave reflections from the boundary; one of the most widely used absorbing layers is Berenger's perfectly matched layer (PML). In this paper, PML is extended to a compound absorbing layer which has multiple effects of damping and deceleration, and is applied to linear and nonlinear Schrödinger equations. The deceleration

    更新日期:2020-10-02
  • Progress on the small modular stellarator SCR-1: new diagnostics and heating scenarios – ERRATUM
    J. Plasma Phys. (IF 2.238) Pub Date : 2020-09-30
    F. Coto-Vílchez; V. I. Vargas; R. Solano-Piedra; M. A. Rojas-Quesada; L. A. Araya-Solano; A. A. Ramírez; M. Hernández-Cisneros; J. E. Pérez-Hidalgo; A. Köhn-Seemann; F. Cerdas; F. Vílchez-Coto; D. Jiménez; L. Campos-Duarte; E. Meneses; M. González-Vega; S. Arias

    This work presents updates in the diagnostics systems, magnetohydrodynamics (MHD) calculations and simulations of microwave heating scenarios of the small modular Stellarator of Costa Rica 1 (SCR-1). Similarly, the design of a flexible bolometer and magnetic diagnostics (a set of Mirnov coils, Rogowski coils and two diamagnetic loops) are introduced. Furthermore, new MHD equilibrium calculations for

    更新日期:2020-09-30
  • Design, construction and utilization of a university plasma laboratory – ERRATUM
    J. Plasma Phys. (IF 2.238) Pub Date : 2020-09-30
    W. Gekelman; P. Pribyl; Z. Lucky; S. W. Tang; J. Han; Y. Qian

    We present the elements required to construct two devices used in an undergraduate plasma physics laboratory. The materials and construction costs of the sources, the vacuum systems and probe drives and electrical circuits are presented in detail in the text and the first appendix. We also provide the software for probe motion and data acquisition as well as the electrical schematics for key components

    更新日期:2020-09-30
  • Overview of the SPARC tokamak
    J. Plasma Phys. (IF 2.238) Pub Date : 2020-09-29
    A. J. Creely; M. J. Greenwald; S. B. Ballinger; D. Brunner; J. Canik; J. Doody; T. Fülöp; D. T. Garnier; R. Granetz; T. K. Gray; C. Holland; N. T. Howard; J. W. Hughes; J. H. Irby; V. A. Izzo; G. J. Kramer; A. Q. Kuang; B. LaBombard; Y. Lin; B. Lipschultz; N. C. Logan; J. D. Lore; E. S. Marmar; K. Montes; R. T. Mumgaard; C. Paz-Soldan; C. Rea; M. L. Reinke; P. Rodriguez-Fernandez; K. Särkimäki; F.

    The SPARC tokamak is a critical next step towards commercial fusion energy. SPARC is designed as a high-field ( $B_0 = 12.2$ T), compact ( $R_0 = 1.85$ m, $a = 0.57$ m), superconducting, D-T tokamak with the goal of producing fusion gain $Q>2$ from a magnetically confined fusion plasma for the first time. Currently under design, SPARC will continue the high-field path of the Alcator series of tokamaks

    更新日期:2020-09-29
  • Predictions of core plasma performance for the SPARC tokamak
    J. Plasma Phys. (IF 2.238) Pub Date : 2020-09-29
    P. Rodriguez-Fernandez; N. T. Howard; M. J. Greenwald; A. J. Creely; J. W. Hughes; J. C. Wright; C. Holland; Y. Lin; F. Sciortino; the SPARC team

    SPARC is designed to be a high-field, medium-size tokamak aimed at achieving net energy gain with ion cyclotron range-of-frequencies (ICRF) as its primary auxiliary heating mechanism. Empirical predictions with conservative physics indicate that SPARC baseline plasmas would reach $Q\approx 11$ , which is well above its mission objective of $Q>2$ . To build confidence that SPARC will be successful,

    更新日期:2020-09-29
  • Projections of H-mode access and edge pedestal in the SPARC tokamak
    J. Plasma Phys. (IF 2.238) Pub Date : 2020-09-29
    J. W. Hughes; N. T. Howard; P. Rodriguez-Fernandez; A. J. Creely; A. Q. Kuang; P. B. Snyder; T. M. Wilks; R. Sweeney; M. Greenwald

    In order to inform core performance projections and divertor design, the baseline SPARC tokamak plasma discharge is evaluated for its expected H-mode access, pedestal pressure and edge-localized mode (ELM) characteristics. A clear window for H-mode access is predicted for full field DT plasmas, with the available 25 MW of design auxiliary power. Additional alpha heating is likely needed for H-mode

    更新日期:2020-09-29
  • Divertor heat flux challenge and mitigation in SPARC
    J. Plasma Phys. (IF 2.238) Pub Date : 2020-09-29
    A. Q. Kuang; S. Ballinger; D. Brunner; J. Canik; A. J. Creely; T. Gray; M. Greenwald; J. W. Hughes; J. Irby; B. LaBombard; B. Lipschultz; J. D. Lore; M. L. Reinke; J. L. Terry; M. Umansky; D. G. Whyte; S. Wukitch; the SPARC Team

    Owing to its high magnetic field, high power, and compact size, the SPARC experiment will operate with divertor conditions at or above those expected in reactor-class tokamaks. Power exhaust at this scale remains one of the key challenges for practical fusion energy. Based on empirical scalings, the peak unmitigated divertor parallel heat flux is projected to be greater than 10 GW m−2. This is nearly

    更新日期:2020-09-29
  • Physics basis for the ICRF system of the SPARC tokamak
    J. Plasma Phys. (IF 2.238) Pub Date : 2020-09-29
    Y. Lin; J. C. Wright; S. J. Wukitch

    Ion cyclotron range of frequencies (ICRF) heating will be the sole auxiliary heating method on SPARC for both full-field (Bt0 ~ 12 T) D–T operation and reduced field (Bt0 ~ 8 T) D–D operation. Using the fast wave at ~120 MHz, good wave penetration and strong single-pass absorption is expected for D–T(3He), D(3He), D(H) and 4He(H) heating scenarios. The dependences of wave absorption on ${k_\parallel

    更新日期:2020-09-29
  • MHD stability and disruptions in the SPARC tokamak
    J. Plasma Phys. (IF 2.238) Pub Date : 2020-09-29
    R. Sweeney; A. J. Creely; J. Doody; T. Fülöp; D. T. Garnier; R. Granetz; M. Greenwald; L. Hesslow; J. Irby; V. A. Izzo; R. J. La Haye; N. C. Logan; K. Montes; C. Paz-Soldan; C. Rea; R. A. Tinguely; O. Vallhagen; J. Zhu

    SPARC is being designed to operate with a normalized beta of $\beta _N=1.0$ , a normalized density of $n_G=0.37$ and a safety factor of $q_{95}\approx 3.4$ , providing a comfortable margin to their respective disruption limits. Further, a low beta poloidal $\beta _p=0.19$ at the safety factor $q=2$ surface reduces the drive for neoclassical tearing modes, which together with a frozen-in classically

    更新日期:2020-09-29
  • Fast-ion physics in SPARC
    J. Plasma Phys. (IF 2.238) Pub Date : 2020-09-29
    S. D. Scott; G. J. Kramer; E. A. Tolman; A. Snicker; J. Varje; K. Särkimäki; J. C. Wright; P. Rodriguez-Fernandez

    Potential loss of energetic ions including alphas and radio-frequency tail ions due to classical orbit effects and magnetohydrodynamic instabilities (MHD) are central physics issues in the design and experimental physics programme of the SPARC tokamak. The expected loss of fusion alpha power due to ripple-induced transport is computed for the SPARC tokamak design by the ASCOT and SPIRAL orbit-simulation

    更新日期:2020-09-29
  • Effects of oblique incidence and colliding pulses on laser-driven proton acceleration from relativistically transparent ultrathin targets
    J. Plasma Phys. (IF 2.238) Pub Date : 2020-09-29
    J. Ferri; E. Siminos; L. Gremillet; T. Fülöp

    The use of ultrathin solid foils offers optimal conditions for accelerating protons to high energies from laser–matter interactions. When the target is thin enough that relativistic self-induced transparency sets in, all of the target electrons get heated to high energies by the laser, which maximizes the accelerating electric field and therefore the final ion energy. In this work, we first investigate

    更新日期:2020-09-29
  • How eigenmode self-interaction affects zonal flows and convergence of tokamak core turbulence with toroidal system size
    J. Plasma Phys. (IF 2.238) Pub Date : 2020-09-28
    Ajay C. J.; Stephan Brunner; Ben McMillan; Justin Ball; Julien Dominski; Gabriele Merlo

    Self-interaction is the process by which a microinstability eigenmode that is extended along the direction parallel to the magnetic field interacts non-linearly with itself. This effect is particularly significant in gyrokinetic simulations accounting for kinetic passing electron dynamics and is known to generate stationary $E\times B$ zonal flow shear layers at radial locations near low-order mode

    更新日期:2020-09-28
  • A class of three-dimensional gyroviscous magnetohydrodynamic models
    J. Plasma Phys. (IF 2.238) Pub Date : 2020-09-22
    Manasvi Lingam; Philip J. Morrison; Alexander Wurm

    A Hamiltonian and action principle formalism for deriving three-dimensional gyroviscous magnetohydrodynamic models is presented. The uniqueness of the approach in constructing the gyroviscous tensor from first principles and its ability to explain the origin of the gyromap and the gyroviscous terms are highlighted. The procedure allows for the specification of free functions, which can be used to generate

    更新日期:2020-09-22
  • Fluctuation dynamo in a weakly collisional plasma
    J. Plasma Phys. (IF 2.238) Pub Date : 2020-09-22
    D. A. St-Onge; M. W. Kunz; J. Squire; A. A. Schekochihin

    The turbulent amplification of cosmic magnetic fields depends upon the material properties of the host plasma. In many hot, dilute astrophysical systems, such as the intracluster medium (ICM) of galaxy clusters, the rarity of particle–particle collisions allows departures from local thermodynamic equilibrium. These departures – pressure anisotropies – exert anisotropic viscous stresses on the plasma

    更新日期:2020-09-22
  • Nonlinear gyrokinetic PIC simulations in stellarators with the code EUTERPE
    J. Plasma Phys. (IF 2.238) Pub Date : 2020-09-17
    E. Sánchez; A. Mishchenko; J. M. García-Regaña; R. Kleiber; A. Bottino; L. Villard; the W7-X team

    In this work, the first nonlinear particle-in-cell simulations carried out in a stellarator with the global gyrokinetic code EUTERPE using adiabatic electrons and realistic plasma parameters are reported. Several studies are conducted with the aim of enabling reliable nonlinear simulations in stellarators with this code. First, EUTERPE is benchmarked against ORB5 in both linear and nonlinear settings

    更新日期:2020-09-18
  • On the polarization of shear Alfvén and acoustic continuous spectra in toroidal plasmas
    J. Plasma Phys. (IF 2.238) Pub Date : 2020-09-16
    M. V. Falessi; N. Carlevaro; V. Fusco; E. Giovannozzi; P. Lauber; G. Vlad; F. Zonca

    In this work, the FALCON code is adopted for illustrating the features of shear Alfvén and sound continuous spectra in toroidal fusion plasmas. The FALCON codes employ the local Floquet analysis discussed in (Phys. Plasmas, vol. 26, issue 8, 2019, 082502) for computing global structures of continuous spectra in general toroidal geometry. As particular applications, reference equilibria for the divertor

    更新日期:2020-09-16
  • Bridging kinetic plasma descriptions and single-fluid models
    J. Plasma Phys. (IF 2.238) Pub Date : 2020-09-15
    A. Crestetto; F. Deluzet; D. Doyen

    The purpose of this paper is to bridge kinetic plasma descriptions and low-frequency single-fluid models. More specifically, the asymptotics leading to magnetohydrodynamic regimes starting from the Vlasov–Maxwell system are investigated. The analogy with the derivation, from the Vlasov–Poisson system, of a fluid representation for ions coupled to the Boltzmann relation for electrons is also outlined

    更新日期:2020-09-15
  • Investigation of turbulent transport regimes in the tokamak edge by using two-fluid simulations
    J. Plasma Phys. (IF 2.238) Pub Date : 2020-09-15
    M. Giacomin; P. Ricci

    The results of flux-driven, two-fluid simulations in single-null configurations are used to investigate the processes determining the turbulent transport in the tokamak edge. Three turbulent transport regimes are identified: (i) a developed transport regime with turbulence driven by an interchange instability, which shares a number of features with the standard L-mode of tokamak operation; (ii) a suppressed

    更新日期:2020-09-15
  • Isotope dependence of energy, momentum and particle confinement in tokamaks
    J. Plasma Phys. (IF 2.238) Pub Date : 2020-09-04
    H. Weisen; C. F. Maggi; M. Oberparleiter; F. J. Casson; Y. Camenen; S. Menmuir; L. Horvath; F. Auriemma; T. W. Bache; N. Bonanomi; A. Chankin; E. Delabie; L. Frassinetti; J. Garcia; C. Giroud; D. King; R. Lorenzini; M. Marin; P. A. Schneider; P. Siren; J. Varje; E. Viezzer; JET contributors

    The isotope dependence of plasma transport will have a significant impact on the performance of future D-T experiments in JET and ITER and eventually on the fusion gain and economics of future reactors. In preparation for future D-T operation on JET, dedicated experiments and comprehensive transport analyses were performed in H, D and H-D mixed plasmas. The analysis of the data has demonstrated an

    更新日期:2020-09-05
  • Island divertor configuration design for a quasi-axisymmetric stellarator CFQS
    J. Plasma Phys. (IF 2.238) Pub Date : 2020-09-02
    S. Okamura; H. Liu; A. Shimizu; S. Kinoshita; M. Isobe; G. Xiong; Y. Xu

    A magnetic field configuration of an island divertor for a quasi-axisymmetric stellarator (CFQS) is proposed. The configuration incorporates large islands surrounding the core confinement region. The interface between the core region and the peripheral region of the island divertor is a clear magnetic separatrix similar to a tokamak divertor. The structure of divertor magnetic field lines is very regular

    更新日期:2020-09-02
  • Theory of the tertiary instability and the Dimits shift within a scalar model
    J. Plasma Phys. (IF 2.238) Pub Date : 2020-08-20
    Hongxuan Zhu; Yao Zhou; I. Y. Dodin

    The Dimits shift is the shift between the threshold of the drift-wave primary instability and the actual onset of turbulent transport in a magnetized plasma. It is generally attributed to the suppression of turbulence by zonal flows, but developing a more detailed understanding calls for consideration of specific reduced models. The modified Terry–Horton system has been proposed by St-Onge (J. Plasma

    更新日期:2020-08-28
  • Gravitating–radiative magnetohydrodynamic surface waves
    J. Plasma Phys. (IF 2.238) Pub Date : 2020-08-27
    R. Ruby; Ch. Rozina; N. L. Tsintsadze; Z. Iqbal

    Radiative-magnetohydrodynamic (RMHD) equations along with a full set of Maxwell's equations are followed to formulate the charged surface waves at the interface of an incompressible, radiative, magnetized dusty plasma and vacuum, while assuming that the characteristic wave frequency is much smaller than the ion gyrofrequency, having an equilibrium background state. It is found that the separation of

    更新日期:2020-08-27
  • Resonance overlap and nonlinear features of the beam–plasma system
    J. Plasma Phys. (IF 2.238) Pub Date : 2020-08-27
    N. Carlevaro; G. Montani; M. V. Falessi

    The beam–plasma instability can be addressed as a reduced model in several contexts of plasma physics, from space to fusion plasma. In this paper, we review and refine some nonlinear features of this model. Specifically, by analysing the dependence of the nonlinear velocity spread as a function of the linear growth rate, we discuss the effective size of the resonance in view of its role in the spectral

    更新日期:2020-08-27
  • On magnetic helicity generation and transport in a nonlinear dynamo driven by a helical flow
    J. Plasma Phys. (IF 2.238) Pub Date : 2020-08-27
    F. Cattaneo; G. Bodo; S. M. Tobias

    The relationship between nonlinear large-scale dynamo action and the generation and transport of magnetic helicity is investigated at moderate values of the magnetic Reynolds number ( $Rm$ ). The model consists of a helically forced, sheared flow in a Cartesian domain. The boundary conditions are periodic in the horizontal and impenetrable for the vertical. The magnetic field is required to be vertical

    更新日期:2020-08-27
  • Perturbing an axisymmetric magnetic equilibrium to obtain a quasi-axisymmetric stellarator
    J. Plasma Phys. (IF 2.238) Pub Date : 2020-08-27
    G. G. Plunk

    It is demonstrated that finite-pressure, approximately quasi-axisymmetric stellarator equilibria can be directly constructed (without numerical optimization) via perturbations of given axisymmetric equilibria. The size of such perturbations is measured in two ways, via the fractional external rotation and, alternatively, via the relative magnetic field strength, i.e. the average size of the perturbed

    更新日期:2020-08-27
  • A relativistic particle pusher for ultra-strong electromagnetic fields
    J. Plasma Phys. (IF 2.238) Pub Date : 2020-08-26
    J. Pétri

    Kinetic plasma simulations are nowadays commonly used to study a wealth of nonlinear behaviours and properties in laboratory and space plasmas. In particular, in high-energy physics and astrophysics, the plasma usually evolves in ultra-strong electromagnetic fields produced by intense laser beams for the former or by rotating compact objects such as neutron stars and black holes for the latter. In

    更新日期:2020-08-26
  • Runaway dynamics in the DT phase of ITER operations in the presence of massive material injection
    J. Plasma Phys. (IF 2.238) Pub Date : 2020-08-25
    O. Vallhagen; O. Embreus; I. Pusztai; L. Hesslow; T. Fülöp

    A runaway avalanche can result in a conversion of the initial plasma current into a relativistic electron beam in high-current tokamak disruptions. We investigate the effect of massive material injection of deuterium–noble gas mixtures on the coupled dynamics of runaway generation, resistive diffusion of the electric field and temperature evolution during disruptions in the deuterium–tritium phase

    更新日期:2020-08-25
  • Particle acceleration in neutron star ultra-strong electromagnetic fields
    J. Plasma Phys. (IF 2.238) Pub Date : 2020-08-25
    Ivan Tomczak; Jérôme Pétri

    In this paper, we discuss the results of a new particle pusher in realistic ultra-strong electromagnetic fields such as those encountered around rotating neutron stars. After presenting the results of this algorithm in simple fields and comparing them to expected exact analytical solutions, we present new simulations for a rotating magnetic dipole in vacuum for a millisecond pulsar by using the Deutsch

    更新日期:2020-08-25
  • Tilting instability of magnetically confined spheromaks
    J. Plasma Phys. (IF 2.238) Pub Date : 2020-08-25
    Riddhi Mehta; Maxim Barkov; Lorenzo Sironi; Maxim Lyutikov

    We consider the tilting instability of a magnetically confined spheromak using three-dimensional magnetohydrodynamic and relativistic particle-in-cell calculations with an application to astrophysical plasmas, specifically those occurring in magnetar magnetospheres. The instability is driven by the counter-alignment of the spheromak's intrinsic magnetic dipole with the external magnetic field. Initially

    更新日期:2020-08-25
  • A Hamiltonian gyrofluid model based on a quasi-static closure
    J. Plasma Phys. (IF 2.238) Pub Date : 2020-08-24
    E. Tassi; T. Passot; P. L. Sulem

    A Hamiltonian six-field gyrofluid model is constructed, based on closure relations derived from the so-called ‘quasi-static’ gyrokinetic linear theory where the fields are assumed to propagate with a parallel phase velocity much smaller than the parallel particle thermal velocities. The main properties captured by this model, primarily aimed at exploring fundamental problems of interest for space plasmas

    更新日期:2020-08-24
  • Enstrophy non-conservation and the forward cascade of energy in two-dimensional electrostatic magnetized plasma turbulence
    J. Plasma Phys. (IF 2.238) Pub Date : 2020-08-20
    G. G. Plunk

    A fluid system is derived to describe electrostatic magnetized plasma turbulence at scales somewhat larger than the Larmor radius of a given species. It is related to the Hasegawa–Mima equation, but does not conserve enstrophy, and, as a result, exhibits a forward cascade of energy, to small scales. The inertial-range energy spectrum is argued to be shallower than a $-11/3$ power law, as compared to

    更新日期:2020-08-20
  • Optimization of finite-build stellarator coils
    J. Plasma Phys. (IF 2.238) Pub Date : 2020-08-20
    Luquant Singh; T. G. Kruger; A. Bader; C. Zhu; S. R. Hudson; D. T. Anderson

    Finding coil sets with desirable physics and engineering properties is a crucial step in the design of modern stellarator devices. Existing stellarator coil optimization codes ultimately produce zero-thickness filament coils. However, stellarator coils have finite depth and thickness, which can make the single-filament model a poor approximation, particularly when coil build dimensions are relatively

    更新日期:2020-08-20
  • Noise-induced magnetic field saturation in kinetic simulations
    J. Plasma Phys. (IF 2.238) Pub Date : 2020-08-17
    J. Juno; M. M. Swisdak; J. M. Tenbarge; V. Skoutnev; A. Hakim

    Monte Carlo methods are often employed to numerically integrate kinetic equations, such as the particle-in-cell method for the plasma kinetic equation, but these methods suffer from the introduction of counting noise to the solution. We report on a cautionary tale of counting noise modifying the nonlinear saturation of kinetic instabilities driven by unstable beams of plasma. We find a saturated magnetic

    更新日期:2020-08-17
  • Kinetic modelling of runaway electron generation in argon-induced disruptions in ASDEX Upgrade
    J. Plasma Phys. (IF 2.238) Pub Date : 2020-08-17
    K. Insulander Björk; G. Papp; O. Embreus; L. Hesslow; T. Fülöp; O. Vallhagen; A. Lier; G. Pautasso; A. Bock; the ASDEX Upgrade Team; the EUROfusion MST1 Team

    Massive material injection has been proposed as a way to mitigate the formation of a beam of relativistic runaway electrons that may result from a disruption in tokamak plasmas. In this paper we analyse runaway generation observed in eleven ASDEX Upgrade discharges where disruption was triggered using massive gas injection. We present numerical simulations in scenarios characteristic of on-axis plasma

    更新日期:2020-08-17
  • Semi-analytic model for the electromagnetic field of a current-driven antenna in a cold, magnetized plasma
    J. Plasma Phys. (IF 2.238) Pub Date : 2020-07-24
    J. Robertson

    In this semi-analytic study we develop a mathematical model for determining the electromagnetic field due to a current-driven antenna immersed in a cold, magnetized plasma, valid for frequencies below the electron plasma frequency. At each point in the plasma, it is shown that the vacuum electric field of the antenna couples to the plasma conductivity tensor and acts as an infinitesimal source term

    更新日期:2020-07-24
  • Diagnosing collisionless energy transfer using field–particle correlations: Alfvén-ion cyclotron turbulence
    J. Plasma Phys. (IF 2.238) Pub Date : 2020-07-24
    Kristopher G. Klein; Gregory G. Howes; Jason M. TenBarge; Francesco Valentini

    We apply field–particle correlations – a technique that tracks the time-averaged velocity-space structure of the energy density transfer rate between electromagnetic fields and plasma particles – to data drawn from a hybrid Vlasov–Maxwell simulation of Alfvén-ion cyclotron turbulence. Energy transfer in this system is expected to include both Landau and cyclotron wave–particle resonances, unlike previous

    更新日期:2020-07-24
  • Conservative discontinuous Galerkin schemes for nonlinear Dougherty–Fokker–Planck collision operators
    J. Plasma Phys. (IF 2.238) Pub Date : 2020-07-17
    Ammar Hakim; Manaure Francisquez; James Juno; Gregory W. Hammett

    We present a novel discontinuous Galerkin algorithm for the solution of a class of Fokker–Planck collision operators. These operators arise in many fields of physics, and our particular application is for kinetic plasma simulations. In particular, we focus on an operator often known as the ‘Lenard–Bernstein’ or ‘Dougherty’ operator. Several novel algorithmic innovations, based on the concept of weak

    更新日期:2020-07-17
  • Solving gyrokinetic systems with higher-order time dependence
    J. Plasma Phys. (IF 2.238) Pub Date : 2020-07-16
    A. Y. Sharma; B. F. McMillan

    We discuss theoretical and numerical aspects of gyrokinetics as a Lagrangian field theory when the field perturbation is introduced into the symplectic part. A consequence is that the field equations and particle equations of motion in general depend on the time derivatives of the field. The most well-known example is when the parallel vector potential is introduced as a perturbation, where a time

    更新日期:2020-07-16
  • Multi-scale dynamics of magnetic flux tubes and inverse magnetic energy transfer
    J. Plasma Phys. (IF 2.238) Pub Date : 2020-07-08
    Muni Zhou; Nuno F. Loureiro; Dmitri A. Uzdensky

    We report on an analytical and numerical study of the dynamics of a three-dimensional array of identical magnetic flux tubes in the reduced-magnetohydrodynamic description of the plasma. We propose that the long-time evolution of this system is dictated by flux-tube mergers, and that such mergers are dynamically constrained by the conservation of the pertinent (ideal) invariants, viz. the magnetic

    更新日期:2020-07-08
  • Progress on the small modular stellarator SCR-1: new diagnostics and heating scenarios
    J. Plasma Phys. (IF 2.238) Pub Date : 2020-07-08
    F. Coto-Vílchez; V. I. Vargas; R. Solano-Piedra; M. A. Rojas-Quesada; L. A. Araya-Solano; A. A. Ramírez; M. Hernández-Cisneros; J. E. Pérez-Hidalgo; A. Köhn-Seemann; F. Cerdas; F. Vílchez-Coto; D. Jiménez; L. Campos-Duarte; E. Meneses; M. González-Vega; S. Arias

    This work presents updates in the diagnostics systems, magnetohydrodynamics (MHD) calculations and simulations of microwave heating scenarios of the small modular Stellarator of Costa Rica 1 (SCR-1). Similarly, the design of a flexible bolometer and magnetic diagnostics (a set of Mirnov coils, Rogowski coils and two diamagnetic loops) are introduced. Furthermore, new MHD equilibrium calculations for

    更新日期:2020-07-08
  • Design, construction and utilization of a university plasma laboratory
    J. Plasma Phys. (IF 2.238) Pub Date : 2020-06-30
    W. Gekelman; P. Pribyl; Z. Lucky; S. W. Tang; J. Han; Y. Qian

    We present the elements required to construct two devices used in an undergraduate plasma physics laboratory. The materials and construction costs of the sources, the vacuum systems and probe drives and electrical circuits are presented in detail in the text and the first appendix. We also provide the software for probe motion and data acquisition as well as the electrical schematics for key components

    更新日期:2020-06-30
  • Global calculation of neoclassical impurity transport including the variation of electrostatic potential
    J. Plasma Phys. (IF 2.238) Pub Date : 2020-06-25
    Keiji Fujita; S. Satake; R. Kanno; M. Nunami; M. Nakata; J. M. García-Regaña; J. L. Velasco; I. Calvo

    Recently, the validity range of the approximations commonly used in neoclassical calculation has been reconsidered. One of the primary motivations behind this trend is observation of an impurity hole in LHD (Large Helical Device), i.e. the formation of an extremely hollow density profile of an impurity ion species, such as carbon $\text{C}^{6+}$ , in the plasma core region where a negative radial electric

    更新日期:2020-06-25
  • Charged particle isotropization in collisionless environments: turbulent magnetic fields as a conduit for random walks
    J. Plasma Phys. (IF 2.238) Pub Date : 2020-06-24
    William I. Newman

    We develop a simple model for the kinematics of charged particles in regions of magnetic turbulence. We approximate the local magnetic field as smoothly varying in strength and direction, where adiabatic invariance prevails, or as presenting rapid changes in direction or ‘kinks’. Particles execute guiding centre gyromotion around a field line. However, in analogy to kinetic theory for collisional environments

    更新日期:2020-06-24
  • Electrodynamics of turbulent fluids with fluctuating electric conductivity
    J. Plasma Phys. (IF 2.238) Pub Date : 2020-06-22
    G. Rüdiger; M. Küker; P. J. Käpylä

    Consequences of fluctuating microscopic conductivity in mean-field electrodynamics of turbulent fluids are formulated and discussed. If the conductivity fluctuations are assumed to be uncorrelated with the velocity fluctuations then only the turbulence-originated magnetic diffusivity of the fluid is reduced and the decay time of a large-scale magnetic field or the cycle times of oscillating turbulent

    更新日期:2020-06-22
  • Effect of the electron redistribution on the nonlinear saturation of Alfvén eigenmodes and the excitation of zonal flows
    J. Plasma Phys. (IF 2.238) Pub Date : 2020-06-19
    A. Biancalani; A. Bottino; P. Lauber; A. Mishchenko; F. Vannini

    Numerical simulations of Alfvén modes driven by energetic particles are performed with the gyrokinetic (GK) global particle-in-cell code ORB5. A reversed shear equilibrium magnetic field is adopted. A simplified configuration with circular flux surfaces and large aspect ratio is considered. The nonlinear saturation of beta-induced Alfvén eigenmodes (BAE) is investigated. The roles of the wave–particle

    更新日期:2020-06-19
  • A family of Vlasov–Maxwell equilibrium distribution functions describing a transition from the Harris sheet to the force-free Harris sheet
    J. Plasma Phys. (IF 2.238) Pub Date : 2020-06-19
    T. Neukirch; F. Wilson; O. Allanson

    We discuss a family of Vlasov–Maxwell equilibrium distribution functions for current sheet equilibria that are intermediate cases between the Harris sheet and the force-free (or modified) Harris sheet. These equilibrium distribution functions have potential applications to space and astrophysical plasmas. The existence of these distribution functions had been briefly discussed by Harrison & Neukirch

    更新日期:2020-06-19
  • Comment on ‘Open-boundary spectral and flux-balance Vlasov simulation by A. Klimas and A. Viñas’
    J. Plasma Phys. (IF 2.238) Pub Date : 2020-06-19
    Alexander J. Klimas; Adolfo. F. Viñas

    An error in Klimas & Viñas (J. Plasma Phys., vol. 85 (6), 2019, 905850610) is noted and explained. It is shown that the results in Klimas and Viñas were unaffected by the error. Further ramifications for future non-periodic spectral simulations are discussed.

    更新日期:2020-06-19
  • Impurity temperature screening in stellarators close to quasisymmetry
    J. Plasma Phys. (IF 2.238) Pub Date : 2020-06-19
    Mike F. Martin; Matt Landreman

    Impurity temperature screening is a favourable neoclassical phenomenon involving an outward radial flux of impurity ions from the core of fusion devices. Quasisymmetric magnetic fields lead to intrinsically ambipolar neoclassical fluxes that give rise to temperature screening for low enough $\unicode[STIX]{x1D702}^{-1}\equiv d\ln n/d\ln T$ . In contrast, neoclassical fluxes in generic stellarators

    更新日期:2020-06-19
  • Studies of the fast ion confinement in the Large Helical Device by using neutron measurement and integrated codes
    J. Plasma Phys. (IF 2.238) Pub Date : 2020-06-17
    H. Nuga; R. Seki; K. Ogawa; S. Kamio; Y. Fujiwara; M. Osakabe; M. Isobe; T. Nishitani; M. Yokoyama; LHD Experiment Group

    The neutral beam (NB) fast ion confinement in the Large Helical Device (LHD) is studied for several full field ( $B_{t}\sim 2.75~\text{T}$ ) magnetic configurations by a combination of neutron measurement and simulations. To investigate the NB fast ion confinement, we have performed a series of short-pulse NB injection experiments. The experiment results are analysed by the integrated code TASK3D-a

    更新日期:2020-06-17
  • Ion kinetic effects on linear pressure driven magnetohydrodynamic instabilities in helical plasmas
    J. Plasma Phys. (IF 2.238) Pub Date : 2020-06-11
    M. Sato; Y. Todo

    The linear MHD (magnetohydrodynamic) stability for high beta plasmas in the inward shifted Large Helical Device (LHD) configurations has been investigated for a wide range of magnetic Reynolds numbers $S$ using numerical simulations based on the kinetic MHD model with kinetic thermal ions where the beta is the ratio of the plasma pressure to the magnetic pressure. It is found that the dependence of

    更新日期:2020-06-11
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