Wilfred Anthony Cooper

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A Hamiltonian/Lagrangian theory to describe guiding centre orbit drift motion which is canonical in the Boozer coordinate frame has been extended to include full electromagnetic perturbed fields in anisotropic pressure 3D equilibria with nested magnetic fl ...

The aim of the present study is to analyze the stability of the pressure gradient driven modes (PM) and Alfven eigenmodes (AE) in the large helical device (LHD) plasma if the rotational transform profile is modified by the current drive of the tangential n ...

The three-dimensional (3-D) VMEC code has been modified to model an energetic species with a variant of a Bi-Maxwellian distribution function that satisfies the constraint B . del F-h = 0, and the 3-D TERPSICHORE stability code has been extended to investi ...

DIII-D physics research addresses critical challenges for the operation of ITER and the next generation of fusion energy devices. This is done through a focus on innovations to provide solutions for high performance long pulse operation, coupled with funda ...

Fast ions in W7-X will be produced either by neutral beam injection (NBI) or by ion-cyclotron resonant heating (ICRH). The latter presents the advantage of depositing power locally and does not suffer from core accessibility issues (Drevlak et al 2014 Nucl ...

Anisotropy and some limiting toroidal flow effects on the stability of nearly resonant ideal magnetohydrodynamic modes in hybrid shaped tokamak plasmas are investigated within the ideal MHD infernal mode framework. Such effects are found to alter the plasm ...

The generation of energetic trapped ions is important for experiments investigating their confinement in 3D magnetic fields, for plasma heating, for studies into unwanted drive of instabilities, and improved transport regimes. An effective way to generate ...

In the first four years of the LHD experiment, several encouraging results have emerged, the most significant of which is that MHD stability and good transport are compatible in the inward shifted axis configuration. The observed energy confinement at this optimal configuration is consistent with ISS95 scaling with an enhancement factor of 1.5. The confinement enhancement over the smaller heliotron devices is attributed to the high edge temperature. We find that the plasma with an average beta of 3% is stab

In current-free stellarators, the parallel current density is normally too weak to drive global external kink modes. However, at finite values of beta, the bootstrap current (BC) can provide sufficient free energy to trigger this class of mode in some stellarator systems. The effect of the BC in the collisionless 1/nu regime has been investigated in several different types of stellarator reactor systems all with a volume V similar to 1000 m(3). In quasiaxisymmetric and quasihelically symmetric stellarators,

One of the main goals of Wendelstein 7-X (W7-X) is to demonstrate the fast particle confinement properties of the quasi-isodynamic stellarator concept. Fast particle populations will be produced either by Neutral Beam Injection (NBI) or by minority Ion Cyc ...

An integrated model capable of self-consistent Ion Cyclotron Resonant Heating (ICRH) simulations has been developed. This model includes both full shaping and pressure effects, warm contributions to the dielectric tensor, pressure anisotropy and finite orb ...

The linear MHD stability problem for 3D plasmas with noninteracting hot electron layers and nested magnetic flux surfaces in the absence of dissipation mechanisms is formulated in variational form. Boozer magnetic coordinates are extended to anisotropic pressure plasmas with nested magnetic flux surfaces for this purpose. A modified energy principle in which the hot electron species current is imperturbable is considered. Plasma incompressibility is imposed and thus a simplified kinetic energy is employed t

Compact optimized stellarators offer novel solutions for confining high-beta plasmas and developing magnetic confinement fusion. The three-dimensional plasma shape can be designed to enhance the magnetohydrodynamic (MHD) stability without feedback or nearby conducting structures and provide drift-orbit confinement similar to tokamaks. These configurations offer the possibility of combining the steady-state low-recirculating power, external control, and disruption resilience of previous stellarators with the

Quiescent H-mode (QH-mode) operation is highly desirable relative to the well known H- mode operation because it allows for high energy density in the core as well as potentially im- proved confinement of energy and particles. A feature of QH-mode is that the Edge Localized Mode (ELM) instabilities are replaced with continuous Edge Harmonic Oscillations (EHO) [1]. Control and reproduction of robust QH-mode regimes could be crucial for future fusion opera- tion. In some cases it may be useful to modify the m

The local and global fluid magnetohydrodynamic stability properties of anisotropic pressure plasmas are investigated with the Kruskal-Oberman and rigid hot particle Johnson et al energy principles. A Heliotron configuration that models the Large Helical De ...

We have investigated the topological modification of an equilibrium with nested magnetic flux surfaces computed with the free boundary variational moments equilibrium code (VMEC) subject to an applied magnetic field perturbation. Magnetic field lines are traced in the domain interior to the plasma-vacuum interface either in the coordinates of the VMEC (s, u, v) or using canonical coordinates (psi, theta*, v) that allow a Hamiltonian description of the magnetic field lines. The perturbation models the effect

The local ideal three dimensional (3-D) magneto-hydrodynamic (MHD) stability for the Wendelstein VTI-X (W VII-X) configuration is studied. A volume averaged beta limit of 5% is confirmed with a nearly optimal pressure profile using two methods to calculate the parallel current density: the magnetic method that uses magnetic information about the configuration (in particular, the condition of charge conservation, del.j = 0, is explicitly used in the resolution) and the geometric method that uses the geometry

Recent experimental results in the Large Helical Device have indicated that a large pressure gradient can be formed beyond the stability criterion for the Mercier (high-n) mode. While the stability against an interchange mode is violated in the inward-shifted configuration due to an enhancement of the magnetic hill, the neoclassical transport and confinement of high-energy particle are, in contrast, improved by this inward shift. Mitigation of the unfavourable effects of MHD instability has led to a signifi

Bifurcated magnetohydrodynamic (MHD) equilibrium states are computed for ITER hybrid scenario and RFX-mod SHAx configurations with very flat or reversed core magnetic shear conditions. In the ITER studies, the minimum inverse rotational transform qmin is n ...

A kinetic-magnetohydrodynamic model with kinetic pressure closure is derived from a consistent guiding-centre framework. Higher-order (gyroviscous) corrections to the pressure tensor are derived in complex geometry from a reduced kinetic equation. The prop ...

Wilfred Anthony Cooper

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Full-field drift Hamiltonian particle orbits in 3D geometry

Effect of the tangential NBI current drive on the stability of pressure and energetic particle driven MHD modes in LHD plasma

Stability properties of anisotropic pressure stellarator plasmas with fluid and noninteractive energetic particles

DIII-D research advancing the physics basis for optimizing the tokamak approach to fusion energy

ICRH induced particle losses in Wendelstein 7-X

Anisotropy and shaping effects on the stability boundaries of infernal ideal MHD modes in tokamak hybrid plasmas

ICRF modelling in 2D and 3D magnetic configurations using a hot plasma model

Recent advances in the LHD experiment

Bootstrap current destabilization of ideal MHD modes in three-dimensional reactor configurations

Fast particle loss channels in Wendelstein 7-X

Integrated modelling of Ion Cyclotron Resonant Heating in toroidal system

Variational Formulation of the Linear Mhd Stability of 3d-Plasmas with Noninteracting Hot-Electrons

Physics of the compact advanced stellarator NCSX

Modelling of non-linear edge harmonic oscillations and the effect of non-axisymmetric magnetic coils

Fluid magnetohydrodynamic stabilit in a heliotron with anisotropic fast particle species

Topologic study of a magnetic perturbation in a 3D free boundary plasma equilibrium

Effect of the Parallel Current-Density on the Local Ideal 3-D Mhd Stability of the Helias Configuration

Configuration flexibility and extended regimes in Large Helical Device

MHD equilibrium and stability of tokamaks and RFP systems with 3D helical cores

Guiding-centre theory for kinetic-magnetohydrodynamic modes in strongly flowing plasmas