A plasma confined in a dipole field exhibits unique equilibrium and stability properties. In particular, equilibria exist at all beta values these are found to be stable ballooning modes when they interchange stable. When kinetic treatment is performed low beta, drift temperature gradient mode also which couples the MHD vicinity of marginal stability.

A comprehensive analysis of the finite-Larmor-radius (FLR) fluid moment equations for collisionless magnetized plasmas is presented. It based on perturbative but otherwise general solutions second and third rank moments (the stress flux tensors), with closure conditions still to be specified fourth moment. The single expansion parameter ratio between largest among gyroradii any other characteristic length, which assumed small finite in a medium. This formalism allows complete account...

An analysis of the stability an arbitrary β collisionless plasma to modes with wavelengths greater than ion gyroradius is presented. The such a perturbations that grow on hydrodynamic time scale determined by Kruskal–Oberman energy principle. However, configuration which predicted be stable basis this kinetic principle may still unstable frequency comparable diamagnetic or curvature drift frequency. A new variational gives sufficient conditions for instability these low- derived. indicates...

The paraxial expansion of a collisionless plasma jet into vacuum, guided by magnetic nozzle, is studied with an Eulerian and non-stationary Vlasov–Poisson solver. Parametric analyzes varying the field rate, size simulation box, electrostatic potential fall are presented. After choosing leading to zero net current beam, steady states simulations exhibit quasi-neutral region followed downstream sheath. latter, unavoidable consequence finite computational domain, does not affect if box chosen...

Molecular dynamics simulations were used to quantify mechanically induced structural evolution in nanocrystalline Al with an average grain size of 5 nm. A polycrystalline sample was cyclically strained at different temperatures, while a recently developed tracking algorithm measure the relative contributions novel deformation mechanisms such as rotation and sliding. Sample texture also tracked during cycling, show how plasticity rearranges overall structure alters boundary network. While no...

The formalism for internal ballooning modes in a tokamak is extended to retain the strong radial variation of ion diamagnetic drift frequency characteristic edge plasmas pedestal region. resulting finite Larmor radius (FLR) stabilization modified and can be weaker than case constant frequency.

The linear stability of high-toroidal-number drift-ballooning modes in tokamaks is investigated with a model that includes resistive and viscous dissipation, assumes the mode frequency to be comparable both sound diamagnetic frequencies. coupled effect ion drift waves electron drift-acoustic shown important, resulting destabilization over an intermediate range toroidal numbers. plasma parameters where assumed orderings hold would applicable edge conditions present day tokamaks, so these...

It is known that tokamaks display a second region of stability to ideal magnetohydrodynamic (MHD) internal modes. An important determining factor for MHD properties the radial profile toroidal current. Here it shown in low-aspect-ratio tokamak with high on-axis safety (q0≂2) and shear, path beta can be obtained remains completely stable against By maintaining shear this scenario avoids fixed boundary instabilities both low mode numbers values well above Troyon limit (stability was tested up...

It is shown experimentally that the lower-hybrid-current-drive density limit a function of rf source frequency. While in previous 800-MHz experiments this occurred at ${\overline{n}}_{e}=6\ifmmode\times\else\texttimes\fi{}{10}^{12}$ ${\mathrm{cm}}^{\ensuremath{-}3}$, with newly installed 2.45-GHz, 100-kW system on Versator II tokamak, fully rf-driven discharges have been achieved densities up to ${\overline{n}}_{e}=1.0\ifmmode\times\else\texttimes\fi{}{10}^{13}$ without increase toroidal...

The ion side of a closed, fluid and drift-kinetic theoretical model to describe slow macroscopic plasma processes in fusion-relevant, low collisionality regime is presented. It follows the ordering assumptions methodology adopted companion electron theory [Ramos, Phys. Plasmas 17, 082502 (2010)]. To reach frequency scale where collisions begin play role, equation for distribution function perturbation away from Maxwellian must be accurate second order Larmor radius. density, flow velocity...

A fluid-kinetic model of the collisionless plasma flow in a convergent-divergent magnetic nozzle is presented. The combines leading-order Vlasov equation and fluid continuity perpendicular momentum for magnetized electrons, equations cold ions, which must be solved iteratively to determine self-consistent response three-dimensional field. kinetic electron solution identifies three populations provides density pressure tensor. far downstream asymptotic behavior shows anisotropic cooling...

Finite Larmor radius (FLR) fluid equations for magnetized plasmas evolving on either sonic or diamagnetic drift time scales are derived consistent with a broad low-collisionality hypothesis. The fundamental expansion parameter is the ratio δ between ion and shortest macroscopic length scale (including fluctuation wavelengths in absence of small turbulence). regime interest specified by assuming that other two basic parameters—namely, electron masses collision cyclotron frequencies—are...

A straightforward operator method is used to derive a form of the drift-kinetic equation for collisionless plasma species in moving reference frame its macroscopic flow. This valid sonic time scales and flow velocities, with first-order finite-Larmor-radius effects included. It applies rigorously far-from-Maxwellian distribution functions general space variations magnetic field. Its velocity moments are shown reproduce exactly corresponding fluid equations obtained from full Vlasov equation.

A closed theoretical model to describe slow, macroscopic plasma processes in a fusion-relevant collisionality regime is set forward. This formulation hybrid one, with fluid conservation equations for particle number, momentum and energy, drift-kinetic closures. Intended realistic application the core of high-temperature tokamak plasma, proposed approach unconventional that ion ordered lower than banana neoclassical theory. The present first part two-article series concerns electron system,...

The stability properties of non-inductively driven, reversed-shear type current profiles that may be achieved for Alcator C-Mod tokamak-like parameters (aspect ratio R/a = 3) are examined. It is found without a conducting wall, the best results ( up to 3.7) highly triangular plasmas at , relatively broad pressure and large values . For elliptical or circular cross-sectional with little triangularity, limits significantly lower ). Finally, more-peaked have beta than broader profiles.

Just above the H-mode threshold power at low density, small amplitude high repetition rate (1-5 kHz) type III edge-localized modes (ELMs) are observed. At higher input power, H-modes become ELM-free. density and (, MW), plasma often enters a new regime now called enhanced H-mode, which is steady-state without distinct ELMs but with levels of emission. Enhanced accompanied by persistent high-frequency broadband (50-400 magnetic fluctuations. Above about , may also exhibit bursting or...

The energy principle is employed to show that the equilibrium confined by magnetic field of a point dipole stable ballooning modes.

The ellipticity criteria for the partial differential equations of axisymmetric single-fluid and Hall magnetohydrodynamic (MHD) equilibria with flow pressure anisotropy are investigated. MHD systems closed cold ions electron pressures derived from their parallel heat flux equations, a closure that reproduces corresponding kinetic dispersion relation. In model, which differs double-adiabatic Chew–Goldberger–Low it is verified elliptic region boundaries occur at poloidal velocities equal to...

A two-fluid analysis of the current driven tearing instability is presented. It concentrates on systematic investigation physics related to plasma compressibility and contribution Hall term inductive electric field, for arbitrary values ion skin depth magnitude magnetic guide field. The treated consistently a wide range beta that excludes only extremely cold limit where mode growth rate would become sonic or supersonic. Conversely, effects associated with finite gyroradius equilibrium...

A combined model for current profile control and MHD stability analysis has been used to identify stable operating modes near the ideal limit (?N 3) in Alcator C-Mod tokamak. These discharges are characterized by relatively high fractions of bootstrap (fBS = 0.70) non-monotonic profiles safety factor with qmin > 2. In absence a conducting shell, was determined onset low (n 1) external kink mode. these studies, plasma periphery (r/a 0.5) provided 2.5-3.0?MW LHCD power. Internal edge transport...

A new code, the Neoclassical Ion-Electron Solver (NIES), has been written to solve for stationary, axisymmetric distribution functions (f) in conventional banana regime both ions and electrons using a set of drift-kinetic equations (DKEs) with linearized Fokker-Planck-Landau collision operators. Solvability conditions on DKEs determine relevant non-adiabatic pieces f (called h). We work 4D phase space which ψ defines flux surface, θ is poloidal angle, v magnitude velocity referenced mean...

It is shown that radial profiles of the safety factor q(r), necessary to access 'second stability' regime in shaped, low aspect ratio tokamaks, can be achieved via off-axis lower hybrid current drive (LHCD). To accurately model required profiles, previous simulation code for LHCD developed by authors has been extended non-circular equilibria and combined with an MHD equilibrium solver. As a particular example, results are presented parameters Versator Upgrade tokamak.

Reduced single-fluid and two-fluid equations for axisymmetric toroidal equilibria of high-beta plasmas with flow are derived by using asymptotic expansions in terms the inverse aspect ratio. Two different orderings velocity, comparable to poloidal Alfvén velocity sound considered. For a poloidal-Alfvénic flow, equilibrium hot ion effects shown have singularity that is shifted gyroviscous cancellation from found singlefluid magnetohydrodynamics (MHD) when equals velocity. poloidal-sonic...

An asymptotic approach to the linear stability of ideal magnetohydrodynamic internal kink mode in large-aspect-ratio tokamak plasmas is presented. This analysis spans arbitrary values plasma pressure gradient, and particular demonstrates stabilization at sufficiently high beta.