R. B. White
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View article: Guiding center equations for the magnetic dipole
Guiding center equations for the magnetic dipole Open
Since the discovery of Van Allen radiation belts in the 1960s, observations of energetic ions trapped in the Earth's dipole magnetic field have illustrated the remarkable confinement properties of this configuration. As such, it has been u…
View article: Poor confinement in stellarators at high energy II
Poor confinement in stellarators at high energy II Open
This work discusses particle resonances in stellarators. There are two important effects. First, resonances provide locations for Alfvén modes, which can cause significant particle loss. Second, if a resonance matches the period of the mod…
View article: Alfvén mode induced particle loss in LHD
Alfvén mode induced particle loss in LHD Open
Losses of beam ions due to Alfvén modes are simulated for discharges in the Large Helical Device at Toki, Japan, using a guiding center code. High frequency beam particle resonances are found for the equilibria for passing particles, provi…
View article: Shifting and Splitting of Resonance Lines due to Dynamical Friction in Plasmas
Shifting and Splitting of Resonance Lines due to Dynamical Friction in Plasmas Open
A quasilinear plasma transport theory that incorporates Fokker-Planck dynamical friction (drag) and pitch angle scattering is self-consistently derived from first principles for an isolated, marginally unstable mode resonating with an ener…
View article: Assessment of radial transport induced by Alfvénic resonances in tokamaks and stellarators
Assessment of radial transport induced by Alfvénic resonances in tokamaks and stellarators Open
In a symmetric plasma confinement device, a perturbation such as an Alfvén mode produces a resonance island which flattens the local energy gradient due to induced rotation about the elliptic points of the resonance. The location of the re…
View article: Testing the conservative character of particle simulations: I. Canonical and noncanonical guiding center model in Boozer coordinates
Testing the conservative character of particle simulations: I. Canonical and noncanonical guiding center model in Boozer coordinates Open
The guiding center (GC) Lagrangian in Boozer coordinates for toroidally confined plasmas can be cast into canonical form by eliminating terms containing the covariant component BΨP of the magnetic field vector with respect to the poloidal …
View article: Extension of the energetic particle transport kick model in TRANSP to multiple fast ion species
Extension of the energetic particle transport kick model in TRANSP to multiple fast ion species Open
Alfvénic instabilities (AEs) are well known to cause enhanced transport of energetic particles (EPs) in fusion devices. Most studies until now have focused on characterizing and understanding AE stability in single-species plasmas heated b…
View article: Momentum transfer and plasma rotation caused by destabilized eigenmodes in tokamaks
Momentum transfer and plasma rotation caused by destabilized eigenmodes in tokamaks Open
The influence of magnetohydrodynamic eigenmodes destabilized by energetic ions on the momentum of these ions and concomitant sheared plasma rotation are studied. Two mechanisms affecting rotation are revealed: (i) spatial channelling (SC) …
View article: Resonant alpha particle loss in stellarators
Resonant alpha particle loss in stellarators Open
Particle resonances in stellarators can produce islands in the space of passing particle orbits without the presence of an unstable Alfvén mode, provided the period of the resonance matches the period of the equilibrium magnetic field. In …
View article: Numerical studies on saturated kink and sawtooth induced fast ion transport in JET ITER-like plasmas
Numerical studies on saturated kink and sawtooth induced fast ion transport in JET ITER-like plasmas Open
This presentation examines the energetic particle transport induced by saturated kink modes and sawtooth crashes in JET deuterium plasmas. It is known that kink mode-resonant transport and phase-space redistribution from sawtooth crashes c…
View article: Testing the conservative character of particle simulations: I. Canonical and noncanonical guiding center model in Boozer coordinates
Testing the conservative character of particle simulations: I. Canonical and noncanonical guiding center model in Boozer coordinates Open
The guiding center (GC) Lagrangian in Boozer coordinates for toroidally confined plasmas can be cast into canonical form by eliminating a term containing the covariant component $B_{Ψ_{\rm P}}$ of the magnetic field vector with respect to …
View article: Poor confinement in stellarators at high energy
Poor confinement in stellarators at high energy Open
High-energy particle resonances can modify particle distributions and even cause significant particle loss. Resonances can be present in any toroidal confinement device and can easily be found numerically. Many stellarators have weak magne…
View article: NSTX-U theory, modeling and analysis results
NSTX-U theory, modeling and analysis results Open
The mission of the low aspect ratio spherical tokamak NSTX-U is to advance the physics basis and technical solutions required for optimizing the configuration of next-step steady-state tokamak fusion devices. NSTX-U will ultimately operate…
View article: Simulating energetic particle losses in JET plasmas with a reverse integration biasing scheme
Simulating energetic particle losses in JET plasmas with a reverse integration biasing scheme Open
An integrated energetic particle transport model has been constructed in JET plasmas constrained by experimental fast ion loss measurements. The model incorporates a synthetic fast ion loss detector identical to JET’s thin-foil Faraday cup…
View article: Development of a reduced model for energetic particle transport by sawteeth in tokamaks
Development of a reduced model for energetic particle transport by sawteeth in tokamaks Open
The sawtooth instability is known for inducing transport and loss of energetic particles (EPs), and for generating seed magnetic islands that can trigger tearing modes. Both effects degrade the overall plasma performance. Several theories …
View article: Particle resonances in stellarators
Particle resonances in stellarators Open
Resonances of high energy particles in magnetic confinement devices due to electromagnetic instabilities can strongly modify the particle distribution, leading to a reduction in fusion power and even discharge termination and particle loss…
View article: Collisionless losses of fast ions in the divertor tokamak test due to toroidal field ripple
Collisionless losses of fast ions in the divertor tokamak test due to toroidal field ripple Open
In this paper we analyze fast ion motion in the divertor tokamak test (DTT) device (Albanese et al 2017 Nucl. Fusion 57 016010). It is planned that DTT will be heated through a mix of 45 MW heating power, including 15 MW negative-ion-based…
View article: On the Effect of Beating during Nonlinear Frequency Chirping
On the Effect of Beating during Nonlinear Frequency Chirping Open
Spectral analyses of energetic particle (EP) driven bursts of MHD\nfluctuations in magnetically confined plasmas often exhibit multiple\nsimultaneous chirps. While the superposition of oscillations at multiple\nfrequencies necessarily caus…
View article: Particle resonances in toroidal fusion devices
Particle resonances in toroidal fusion devices Open
Resonances of high energy particles in magnetic confinement devices due to electromagnetic instabilities can strongly modify the distribution, leading to a reduction in fusion power and even discharge termination and particle loss to the d…
View article: Numerical investigation of alpha particle confinement under the perturbation of neoclassical tearing modes and toroidal field ripple in CFETR
Numerical investigation of alpha particle confinement under the perturbation of neoclassical tearing modes and toroidal field ripple in CFETR Open
The confinement of alpha particles in burning plasma is a key issue in fusion reactor design, including particle interaction with instabilities. This paper includes two topics: the effect of neoclassical tearing modes (NTMs) and toroidal f…
View article: Alpha particle channeling in ITER
Alpha particle channeling in ITER Open
Alpha particle channeling, the attempt to extract energy from high-energy fusion alpha particles using a combination of high- and low-frequency waves introduced in the plasma with antennae, is studied using a guiding center code. We examin…
View article: Shifting and splitting of resonance lines due to dynamical friction in plasmas
Shifting and splitting of resonance lines due to dynamical friction in plasmas Open
A quasilinear plasma transport theory that incorporates Fokker-Planck dynamical friction (drag) and pitch angle scattering is self-consistently derived from first principles for an isolated, marginally-unstable mode resonating with an ener…
View article: Phase-space dynamics of Alfvén mode chirping
Phase-space dynamics of Alfvén mode chirping Open
In tokamak discharges, toroidal Alfvén eigenmodes often experience complex semi-periodic frequency modulation known as chirping. These events modify the local high energy particle distribution and are expected to occur in many future fusio…
View article: Spatial channeling in toroidal plasmas: overview and new results
Spatial channeling in toroidal plasmas: overview and new results Open
Energy and momentum transfer by eigenmodes in tokamaks and stellarators, which arises when eigenmodes are destabilized by superthermal ions in a region that does not coincide with the damping region, is considered. This phenomenon, named s…
View article: Simulation of Alfvénic avalanche onset in NSTX
Simulation of Alfvénic avalanche onset in NSTX Open
In some tokamak discharges, a number of Alfvén eigenmodes (AEs) have been observed to cause a large-scale collapse of the high energy particle distribution, a phenomenon referred to as an avalanche. We examine the necessary conditions for …
View article: Reduced energetic particle transport models enable comprehensive time-dependent tokamak simulations
Reduced energetic particle transport models enable comprehensive time-dependent tokamak simulations Open
Time-dependent integrated simulations through codes such as TRANSP are becoming an indispensable tool for the interpretation of existing experiments and predictions of optimized scenarios. For many practical cases, quantitative simulations…
View article: Verification and application of resonance broadened quasi-linear (RBQ) model with multiple Alfvénic instabilities
Verification and application of resonance broadened quasi-linear (RBQ) model with multiple Alfvénic instabilities Open
The resonance broadened quasilinear (RBQ) model for the problem of relaxing the hot ion distribution function in constant-of-motion 3D space [Gorelenkov et al., Nucl. Fusion 58, 082016 (2018)] is presented with the self-consistent evolutio…
View article: The collisional resonance function in discrete-resonance quasilinear plasma systems
The collisional resonance function in discrete-resonance quasilinear plasma systems Open
A method is developed to analytically determine the resonance broadening function in quasilinear theory, due to either Krook or Fokker-Planck scattering collisions of marginally unstable plasma systems where discrete resonance instabilitie…
View article: A simple model for perturbative kinetic particle resonances in tokamaks
A simple model for perturbative kinetic particle resonances in tokamaks Open
Resonances driven by particle distribution gradients are studied in a simple statistical model which does not involve advancing individual particles due to the interaction with the mode. The phase-space structure of resonances and the asso…