N. C. Hurst
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View article: Characterization and stability of helical density snake structures in Madison Symmetric Torus tokamak plasmas
Characterization and stability of helical density snake structures in Madison Symmetric Torus tokamak plasmas Open
Steady, helical perturbations known as ‘density snakes’ with poloidal and toroidal mode numbers $m=1$ , $n=1$ have been studied in several tokamak experiments. These three-dimensional, helical states are interesting due to their stability …
View article: MagNetUS: a magnetized plasma research ecosystem
MagNetUS: a magnetized plasma research ecosystem Open
MagNetUS is a network of scientists and research groups that coordinates and advocates for fundamental magnetized plasma research in the USA. Its primary goal is to bring together a broad community of researchers and the experimental and n…
View article: All-in-one probe for exploring self-organized two-fluid equilibria in toroidal plasmas
All-in-one probe for exploring self-organized two-fluid equilibria in toroidal plasmas Open
This paper presents the development of an all-in-one probe to simultaneously measure all components of the generalized Ohm’s law in reversed-field pinch plasmas and tokamaks. The polyhedral configuration of the Mach probe is achieved throu…
View article: Tokamak Plasmas with Density up to 10 Times the Greenwald Limit
Tokamak Plasmas with Density up to 10 Times the Greenwald Limit Open
Current-carrying, toroidal laboratory plasmas typically cannot be sustained with an electron density above the empirical Greenwald limit. Presented here are tokamak experiments in the Madison Symmetric Torus with a density up to an unprece…
View article: Vortex splitting in two-dimensional fluids and non-neutral electron plasmas with smooth vorticity profiles
Vortex splitting in two-dimensional fluids and non-neutral electron plasmas with smooth vorticity profiles Open
Initially, elliptical, quasi-two-dimensional (2D) fluid vortices can split into multiple pieces if the aspect ratio is sufficiently large due to the growth and saturation of perturbations known as Love modes on the vortex edge. Presented h…
View article: Physics of the thermal quench in MST tokamak plasmas (Final Technical Report)
Physics of the thermal quench in MST tokamak plasmas (Final Technical Report) Open
This project at the University of Wisconsin-Madison targeted measurements in tokamak plasmas in the Madison Symmetric Torus (MST) to help elucidate the physics of the tokamak disruption. We intended to focus on the thermal quench, during w…
View article: MST resistive wall tearing mode simulations
MST resistive wall tearing mode simulations Open
The Madison Symmetric Torus (MST) is a toroidal device that, when operated as a standard tokamak, does not have major disruptions. Unlike most tokamaks, the MST plasma is surrounded by a close fitting highly conducting wall, with a resisti…
View article: Self-organized magnetic equilibria in tokamak plasmas with very low edge safety factor
Self-organized magnetic equilibria in tokamak plasmas with very low edge safety factor Open
Tokamak plasmas often exhibit self-organizing behavior in which internal modes shape the toroidal current density profile, a common example being the sawtooth instability. However, such behavior has not been studied in detail for edge safe…
View article: Inviscid damping of an elliptical vortex subject to an external strain flow
Inviscid damping of an elliptical vortex subject to an external strain flow Open
Inviscid spatial Landau damping is studied experimentally for the case of oscillatory motion of a two-dimensional vortex about its elliptical equilibrium in the presence of an applied strain flow. The experiments are performed using electr…
View article: Computational study of runaway electrons in MST tokamak discharges with applied resonant magnetic perturbation
Computational study of runaway electrons in MST tokamak discharges with applied resonant magnetic perturbation Open
A numerical study of magnetohydrodynamics (MHD) and tracer-particle evolution investigates the effects of resonant magnetic perturbations (RMPs) on the confinement of runaway electrons (REs) in tokamak discharges conducted in the Madison S…
View article: Multi-energy reconstructions, central electron temperature measurements, and early detection of the birth and growth of runaway electrons using a versatile soft x-ray pinhole camera at MST
Multi-energy reconstructions, central electron temperature measurements, and early detection of the birth and growth of runaway electrons using a versatile soft x-ray pinhole camera at MST Open
A multi-energy soft x-ray pinhole camera has been designed, built, and deployed at the Madison Symmetric Torus to aid the study of particle and thermal transport, as well as MHD stability physics. This novel imaging diagnostic technique em…
View article: Adiabatic behavior of an elliptical vortex in a time-dependent external strain flow
Adiabatic behavior of an elliptical vortex in a time-dependent external strain flow Open
The adiabatic behavior of two-dimensional (2D) fluid vortices subject to slowly varying, time-dependent external strain flows is studied theoretically, and experimentally using magnetized non-neutral electron plasmas. Here the E × B drift …
View article: Instability of an electron-plasma shear layer in an externally imposed strain flow
Instability of an electron-plasma shear layer in an externally imposed strain flow Open
The E×B shear instability of a two-dimensional (2D) filament (i.e., a thin, rectangular strip perpendicular to the magnetic field) of magnetized pure electron plasma is investigated experimentally in the presence of an externally imposed s…
View article: Confinement and manipulation of electron plasmas in a multicell trap
Confinement and manipulation of electron plasmas in a multicell trap Open
Plasma dynamics and transport are studied experimentally in a multicell Penning-Malmberg trap. The goal is to develop methods for accumulation and long-term confinement of larger numbers of charged particles (e.g., positrons) than is prese…
View article: Electron vortices subject to imposed strain flows
Electron vortices subject to imposed strain flows Open
The stability and dynamics of two-dimensional (2D) ideal fluid vortices are studied under the influence of externally imposed irrotational strain flows. Laboratory experiments are conducted using pure electron plasmas. This is made possibl…
View article: Evolution of a Vortex in a Strain Flow
Evolution of a Vortex in a Strain Flow Open
Experiments and vortex-in-cell simulations are used to study an initially axisymmetric, spatially distributed vortex subject to an externally imposed strain flow. The experiments use a magnetized pure electron plasma to model an inviscid t…
View article: Magnetic field extraction of trap-based electron beams using a high-permeability grid
Magnetic field extraction of trap-based electron beams using a high-permeability grid Open
A method to form high quality electrostatically guided lepton beams is explored. Test electron beams are extracted from tailored plasmas confined in a Penning-Malmberg trap. The particles are then extracted from the confining axial magneti…