Your search
Results 15 resources
-
In magnetic confinement fusion devices, the ratio of the plasma pressure to the magnetic field energy, beta, can become sufficiently large that electromagnetic microinstabilities become unstable, driving turbulence that distorts or reconnects the equilibrium magnetic field. In this paper, a theory is proposed for electromagnetic, electron-driven linear instabilities that have current layers...
-
Linear perturbation theory is used to model the ideal magnetohydrodynamic stability of tokamak equilibria under the application of external 3D magnetic perturbations (Hegna 2014 Phys. Plasmas 21 072502). We use the ELITE code (Wilson et al 2002 Phys. Plasmas 9 1277) to produce both a linear plasma response, as well as the linear axisymmetric toroidal eigenmodes which are used as basis...
-
The high heat fluxes to the divertor during edge localised mode (ELM) instabilities have to be reduced for a sustainable future tokamak reactor. A solution to reduce the heat fluxes could be the Super-X divertor, which will be tested on MAST-U. ELM simulations for MAST-U Super-X tokamak plasmas have been obtained, using JOREK. A factor 10 decrease in the peak heat flux to the outer target and...
-
Nonlinear multiscale gyrokinetic simulations of a Joint European Torus edge pedestal are used to show that electron-temperature-gradient (ETG) turbulence has a rich three-dimensional structure, varying strongly according to the local magnetic-field configuration. In the plane normal to the magnetic field, the steep pedestal electron temperature gradient gives rise to anisotropic turbulence...
-
The work reported in this paper addresses two aspects. In the first part, numerical simulations are conducted to examine the impact of magnetic equilibrium shaping (elongation and triangularity), on both conventional Ion Temperature Gradient (ITG) modes and Short Wavelength ITG modes. This analysis is performed considering the experimental profiles and parameters of the ADITYA-U tokamak,...
-
High-power-density tokamaks offer a potential solution to design cost-effective fusion devices. One way to achieve high power density is to operate at a high ββ\beta value (the ratio of thermal to magnetic pressure), i.e. β∼1β∼1\beta \sim 1. However, a β∼1β∼1\beta \sim 1 state may be unstable to various pressure- and current-driven instabilities or have unfavourable microstability properties....
-
We present herein the results of a linear gyrokinetic analysis of electromagnetic microinstabilites in the conceptual high reactor-scale, tight-aspect-ratio tokamak Spherical Tokamak for Energy Production, https://step.ukaea.uk. We examine a range of flux surfaces between the deep core and the pedestal top for two candidate flat-top operating points of the prototype device. Local linear...
-
First nonlinear gyrokinetic simulations of microtearing modes in the core of a MAST case are performed on two surfaces of the high-collisionality discharge used in Valovič et al (2011 Nucl. Fusion 51 073045) to obtain the favorable energy confinement scaling with collisionality, . On the considered surfaces microtearing modes dominate linearly at binormal length scales of the order of the ion...
-
A new drift kinetic theory for the plasma response to the neoclassical tearing mode (NTM) magnetic perturbation is presented. Small magnetic islands of width, (a is the tokamak minor radius) are assumed, retaining the limit w ∼ ρ bi (ρ bi is the ion banana orbit width) to include finite orbit width effects. When collisions are small, the ions/electrons follow streamlines in phase space; for...
-
Microtearing modes have been widely reported as a tearing parity electron temperature gradient driven plasma instability, which leads to fine scale tearing of the magnetic flux surfaces thereby resulting in reconnection of magnetic field lines and formation of magnetic islands. In slab geometry it has previously been shown that the drive mechanism requires a finite collision frequency....
-
Two synthetic diagnostics are implemented for the high-k scattering system in NSTX (Smith et al 2008 Rev. Sci. Instrum. 79 123501) allowing direct comparisons between the synthetic and experimentally detected frequency and wavenumber spectra of electron-scale turbulence fluctuations. Synthetic diagnostics are formulated in real-space and in wavenumber space, and are deployed in realistic...
-
The strong, sharp flow structures that are seen frequently in tokamak cores, and large amplitude spontaneous global toroidal rotation are both surprising in light of current theories where toroidal flow evolution is dominantly diffusive. Mechanisms for spontaneously generating strong poloidal shear flows have been extensively investigated, but these processes were thought not to apply to...
-
Planar periodic surface lattice (PSL) structures based on thin, subwavelength substrates have been studied experimentally and numerically. Coupled eigenmode resonances composed of partial volume and surface modes are observed for PSLs with lattice periodicities of 1.50 mm and 1.62 mm etched onto thin copper-backed, substrates. We show that the copper backing is essential for mode-selection in...
-
This paper describes a model of electron energization and cyclotron-maser emission applicable to astrophysical magnetized collisionless shocks. It is motivated by the work of Begelman, Ergun and Rees [Astrophys. J. 625, 51 (2005)] who argued that the cyclotron-maser instability occurs in localized magnetized collisionless shocks such as those expected in blazar jets. We report on recent...
-
We propose that pressure anisotropy causes weakly collisional turbulent plasmas to self-organize so as to resist changes in magnetic-field strength. We term this effect ‘magneto-immutability’ by analogy with incompressibility (resistance to changes in pressure). The effect is important when the pressure anisotropy becomes comparable to the magnetic pressure, suggesting that in collisionless,...
Explore
Topic
Outputs
- Publications (15)
Resource type
- Journal Article (15)