A5034320303- Magnetic confinement fusion research
- Plasma Diagnostics and Applications
- Ionosphere and magnetosphere dynamics
- Laser-induced spectroscopy and plasma
- Atomic and Molecular Physics
- Solar and Space Plasma Dynamics
- Superconducting Materials and Applications
- Laser Design and Applications
- Particle accelerators and beam dynamics
- Fluid Dynamics and Turbulent Flows
- Muon and positron interactions and applications
- Laser-Plasma Interactions and Diagnostics
- Solid State Laser Technologies
- Vibration and Dynamic Analysis
- Mass Spectrometry Techniques and Applications
- Advanced Data Storage Technologies
- Dust and Plasma Wave Phenomena
- Fluid Dynamics and Vibration Analysis
- Electrostatic Discharge in Electronics
- Lattice Boltzmann Simulation Studies
- Calibration and Measurement Techniques
- Tropical and Extratropical Cyclones Research
- Quantum optics and atomic interactions
- Fusion materials and technologies
- Electromagnetic Simulation and Numerical Methods
University of Wisconsin–Madison
2010-2024
University of California, San Diego
2013-2022
Princeton Plasma Physics Laboratory
2021-2022
Oak Ridge National Laboratory
2022
National Institutes for Quantum Science and Technology
2021
Kyushu University
2021
Edgewood College
2021
The University of Tokyo
2021
MagNetUS is a network of scientists and research groups that coordinates advocates for fundamental magnetized plasma in the USA. Its primary goal to bring together broad community researchers experimental numerical tools they use order facilitate sharing ideas, resources common tasks. Discussed here are motivation goals this details its formation, history structure. An overview associated facilities projects provided, along with examples scientific topics investigated therein. Finally,...
The pulse from a transversely excited atmospheric CO(2) laser consists of sharp spike followed by long, drawn out tail region spanning about 2-5 micros caused the nitrogen gas in cavity. is undesirable many applications because it decreases average power pulse. We employ pinhole plasma shutter for eliminating and shortening width. optically triggers at certain point time with respect to temporal profile This way, good portion transmitted, while energy stored consumed heating plasma....
Experiments and vortex-in-cell simulations are used to study an initially axisymmetric, spatially distributed vortex subject externally imposed strain flow. The experiments use a magnetized pure electron plasma model inviscid two-dimensional fluid. results compared theory assuming elliptical region of constant vorticity. For relatively flat vorticity profiles, the dynamics stability threshold in close quantitative agreement with theory. Physics beyond constant-vorticity model, such as...
Initially, elliptical, quasi-two-dimensional (2D) fluid vortices can split into multiple pieces if the aspect ratio is sufficiently large due to growth and saturation of perturbations known as Love modes on vortex edge. Presented here are experiments numerical simulations, showing that threshold for splitting significantly higher with realistic, smooth edges than predicted by a simple “vortex patch” model, where vorticity treated piecewise constant inside deformable boundary. The conducted...
Current-carrying, toroidal laboratory plasmas typically cannot be sustained with an electron density above the empirical Greenwald limit. Presented here are tokamak experiments in Madison Symmetric Torus a up to unprecedented level about 10 times this This is thought made possible part by thick, stabilizing, conductive wall, and high-voltage, feedback-controlled power supply driving plasma current. The radial profile of current flattens around twice limit, without edge collapse routinely...
Abstract The Madison Symmetric Torus (MST) is a toroidal device that, when operated as standard tokamak, does not have major disruptions. Unlike most tokamaks, the MST plasma surrounded by close fitting highly conducting wall, with resistive wall penetration time two orders of magnitude longer than in JET or DIII-D, and three times ITER. can operate edge <?CDATA $q_a \leqslant 2$?> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:msub>...
This paper presents the development of an all-in-one probe to simultaneously measure all components generalized Ohm’s law in reversed-field pinch plasmas and tokamaks. The polyhedral configuration Mach is achieved through specific arrangement, angle, depth collimator channel apertures drilled into surface a hollow boron nitride cylinder encasing it. includes central assess ion velocity field three dimensions. Initial tests at RELAX Madison Symmetric Torus machines have confirmed probe’s...
Chirped-frequency autoresonant excitation of the diocotron mode is used to move electron plasmas confined in a Penning-Malmberg trap across magnetic field for advanced plasma and antimatter applications. Plasmas 108 electrons, with radii small compared that confining electrodes, can be moved from axis ≥90% electrode radius near unit efficiency reliable angular positioning. Translations ≥70% wall are possible wider range parameters. Details this process, including phase displacement...
Tokamak plasmas often exhibit self-organizing behavior in which internal modes shape the toroidal current density profile, a common example being sawtooth instability. However, such has not been studied detail for edge safety factor below 2 due to disruptive kink instabilities that typically prevent operation this regime. Now, steady tokamak with an down 0.8 have created Madison Symmetric Torus, where disruptions are prevented thick, conductive wall and feedback power supply sustains plasma...
The perpendicular dynamics of a pure electron plasma column are investigated when the spans two Penning-Malmberg traps with noncoinciding axes. executes noncircular orbits described by competing image-charge electric-field (diocotron) drifts from traps. A simple model is presented that predicts set nested in agreement observed trajectories.
Plasma dynamics and transport are studied experimentally in a multicell Penning-Malmberg trap. The goal is to develop methods for accumulation long-term confinement of larger numbers charged particles (e.g., positrons) than presently possible. In this scheme, the constitute non-neutral plasmas which confined separately parallel array storage cells. Experiments presented pure electron transferred from large-diameter “master cell” trapping region into four smaller, “storage cells,” three...
When vortex patches are subjected to externally imposed strain flows where the rate grows slowly in time, system approximately preserves an adiabatic invariant related oscillatory elliptical deformations of vortices. Formulae derived for breaking this with respect and functional form ramp. The analytical results compared experimental data acquired using magnetized pure electron plasmas, which provide a close laboratory realization motion two-dimensional ideal
A pulse-burst laser has been installed for Thomson scattering measurements on the Madison Symmetric Torus reversed-field pinch. The design is a master-oscillator power-amplifier. master oscillator commercial Nd:YVO(4) (1064 nm) which capable of Q-switching at frequencies between 5 and 250 kHz. Four Nd:YAG (yttrium aluminum garnet) amplifier stages are in place to amplify emission. Single pulses through gives energies up 1.5 J gain each stage measured. Repetitive pulsing 10 kHz also performed...
A method to form high quality electrostatically guided lepton beams is explored. Test electron are extracted from tailored plasmas confined in a Penning-Malmberg trap. The particles then the confining axial magnetic field by passing them through permeability grid with radial tines (a so-called “magnetic spider”). An Einzel lens used focus and analyze beam properties. Numerical simulations model non-adiabatic effects due spider, predictions compared experimental results. Improvements...
The dynamics of two-dimensional (2-D) ideal fluid vortices is studied experimentally in the presence an irrotational strain flow. Laboratory experiments are conducted using strongly magnetized pure electron plasmas, a technique which made possible by isomorphism between drift–Poisson equations describing plasma transverse to field and 2-D Euler fluid. system provides excellent opportunity study due weak dissipation 3-D effects, simple diagnosis precise control. confinement apparatus used...
Described here is progress in an experimental program to develop a 21 cell multicell trap for the accumulation and storage of ∼ 1012 positrons. The basic architecture arrangement multiple Penning-Malmberg (PM) trapped plasmas (i.e., cells) arranged parallel common vacuum system magnetic field. Experiments are described that intended address several key issues, including effects large space charge potentials high plasma densities on: heating, deterioration confinement, decreased efficiency...
The E×B shear instability of a two-dimensional (2D) filament (i.e., thin, rectangular strip perpendicular to the magnetic field) magnetized pure electron plasma is investigated experimentally in presence an externally imposed strain flow. Data are acquired using specialized Penning–Malmberg trap which flows can be applied 2D by biasing segmented electrodes surrounding plasma. drift dynamics well-described Drift-Poisson equations, isomorphic Euler equations describing ideal fluids. Thus,...
A multi-energy soft x-ray pinhole camera has been designed, built, and deployed at the Madison Symmetric Torus to aid study of particle thermal transport, as well MHD stability physics. This novel imaging diagnostic technique employs a pixelated detector in which lower energy threshold for photon detection can be adjusted independently on each pixel. The choice is PILATUS3 100 K with 450 μm thick silicon sensor nearly 000 pixels sensitive energies between 1.6 30 keV. An ensemble cubic spline...
A numerical study of magnetohydrodynamics (MHD) and tracer-particle evolution investigates the effects resonant magnetic perturbations (RMPs) on confinement runaway electrons (REs) in tokamak discharges conducted Madison Symmetric Torus. In computational results applying RMPs having a broad toroidal spectrum but single poloidal harmonic, m = 1 RMP does not suppress REs, whereas 3 achieves significant deconfinement complete suppression obtained experiment [Munaretto et al., Nuclear Fusion 60,...
An experimental technique is presented for studying two-dimensional (2D) ideal fluid vortices in the presence of externally imposed flows, using an electron plasma confined a Penning-Malmberg trap. This procedure made possible by isomorphism between Drift-Poisson equations governing dynamics and 2D Euler describing fluid. Here, density analog vorticity, electric potential that stream function. External flows are segmented electrode spanning length plasma. Details data analysis given,...
The m = 1 diocotron mode is an important feature of the dynamics single-component plasmas confined in Penning-Malmberg traps. Presented here are calculations frequency under conditions where most commonly used approximations invalid. One application calculation described operation a multi-cell trap that employs low-aspect-ratio “master” cell. Measurements prototype device presented. predictions good agreement with data, even for amplitudes approaching inner radius electrodes.
Recent progress is described to implement two approaches specially tailor trap-based positron beams. Experiments and simulations are presented understand the limits on energy spread pulse duration of beams extracted from a Penning-Malmberg (PM) trap after particles have been buffer-gas cooled (or heated) in range temperatures 1000 ≥ T 300 K. These also used predict beam performance for cryogenically positrons. properties formed when plasmas tailored PM 5 tesla magnetic field, then...
Inviscid spatial Landau damping is studied experimentally for the case of oscillatory motion a two-dimensional vortex about its elliptical equilibrium in presence an applied strain flow. The experiments are performed using electron plasmas Penning–Malmberg trap. They exploit isomorphism between Euler equations ideal fluid and drift-Poisson plasma, where plasma density analog vorticity. Perturbed states created E×B flows, which generated by applying voltages to electrodes surrounding plasma....
Calibration of the Madison Symmetric Torus Thomson scattering system has been refined to improve temperature fluctuation measurements. Multiple avalanche photodiodes have directly calibrated for use as reference detectors during calibration, improving accuracy and ease use. From absolute calibration we calculate corrections gain variation in detector operating temperature. We also measure spatial uniformity responsivity several photodiodes, present a method accounting non-uniformity process....