A5008017249- Magnetic confinement fusion research
- Plasma Diagnostics and Applications
- Ionosphere and magnetosphere dynamics
- Particle accelerators and beam dynamics
- Laser-Plasma Interactions and Diagnostics
- Laser-induced spectroscopy and plasma
- Atomic and Molecular Physics
- Solar and Space Plasma Dynamics
- Laser Design and Applications
- Electron and X-Ray Spectroscopy Techniques
- Gas Dynamics and Kinetic Theory
- Nuclear Physics and Applications
- Atomic and Subatomic Physics Research
- Silicon and Solar Cell Technologies
- Semiconductor materials and devices
- Superconducting Materials and Applications
- Particle Accelerators and Free-Electron Lasers
- Spectroscopy and Laser Applications
- Advancements in Semiconductor Devices and Circuit Design
- Spacecraft and Cryogenic Technologies
- Metal and Thin Film Mechanics
- X-ray Spectroscopy and Fluorescence Analysis
- Magnetic Field Sensors Techniques
- Medical Imaging Techniques and Applications
- Quantum, superfluid, helium dynamics
University of Wisconsin–Madison
2001-2024
Wheaton College - Illinois
2016
Sterling Research Group
2002
University of Wisconsin System
1995
An overview of recent results from the MST programme on physics important for advancement reversed field pinch (RFP) as well improved understanding toroidal magnetic confinement more generally is reported. Evidence classical ions in RFP provided by analysis impurity and energetic created 1 MW neutral beam injection (NBI). The first appearance energetic-particle-driven modes NBI a plasma described. plasmas robustly access quasi-single-helicity state that has commonalities to stellarator...
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...
A cause of observed anomalous plasma momentum transport in a reversed-field pinch is determined experimentally. Magnetohydrodynamic theory predicts that nonlinear interactions involving triplets tearing modes produce internal torques redistribute momentum. Evidence for the torque acquired by detecting correlation redistribution with mode triplets, elimination one triplet, and external driving modes.
An overview of recent results from the MST reversed field pinch programme is presented. With neutral beam injection, bursty energetic particle (EP) modes are observed. The profiles magnetic and density fluctuations associated with these EP measured using a far infrared interferometer–polarimeter. Equilibrium reconstructions quasi-single-helicity 3D helical state provided by V3FIT code that now incorporates several MST's advanced diagnostics. orientation structure controlled new resonant...
A soft x-ray (SXR) diagnostic to measure electron temperature on the Madison Symmetric Torus using two complementary methods is presented. Both are based double-foil technique, which calculates via ratio of SXR bremsstrahlung emission from plasma in different energy ranges. The tomographic emissivity method applies technique a reconstruction emissivity, creating two-dimensional map throughout plasma. In contrast, direct brightness directly measured and generates vertical horizontal radial...
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...
Many plasma diagnostics contain complementary information. For example, the double-foil soft x-ray system (SXR) and Thomson Scattering diagnostic (TS) on Madison Symmetric Torus both measure electron temperature. The information from these can be combined using a systematic method based integrated data analysis techniques, leading to more accurate sensitive results. An tool Bayesian probability theory was able estimate temperatures that are consistent with SXR TS precise than either. A...
The upgraded spectrometer used for charge exchange recombination spectroscopy on the Madison Symmetric Torus resolves emission fluctuations up to 400 kHz. transimpedance amplifier's cutoff frequency was increased based upon simulations comparing change in measured photon counts time-dynamic signals. We modeled each signal-processing stage of diagnostic and scanned filtering quantify uncertainty counting rate. This modeling showed that uncertainties can be calculated assuming amplification is...
We have developed a low-cost, robust, multifoil-filtered spectrometer to provide absolute measurements of low-Z impurity concentrations in the Madison Symmetric Torus reversed-field pinch. The utilizes an array six thin-film coated soft x-ray diodes. Each multilayered coating is specifically tailored isolate K-shell emission lines H- and He-like oxygen, carbon, aluminum. With calibrations obtained via synchrotron source, photon flux been made. address technical aspects this diagnostic...
An Ion Doppler Spectrometer (IDS) is used for fast measurements of C VI line emission (343.4 nm) in the Madison Symmetric Torus. Absolutely calibrated flow are difficult because IDS records data within 0.25 nm line. Commercial calibration lamps do not produce lines this narrow range. A light source using an ultraviolet LED and etalon was designed to provide a fiducial marker 0.08 wide. The coupled into at f/4, holographic diffuser increases homogeneity final image. Random systematic errors...
A set of two newly designed, single-channel Czerny–Turner spectrometers has been deployed at the DIII-D tokamak for measurements motional Stark effect (MSE) split beam emission and C6+ (CVI) carbon charge exchange recombination (CER) high spectral (δλ = 0.13 nm) temporal (1–5 kHz) resolution. High throughput optics (f/# 2.8) allow good signal-to-noise time resolution using fast EMCCD detectors. The MSE allows fitting magnitude direction local B-field, while yields ion temperature toroidal...
This paper presents progress made toward the overarching goal to adapt single-photon-counting microcalorimeters magnetic fusion energy research and demonstrate value of such measurements for fusion. Microcalorimeter spectrometers combine best characteristics x-ray instrumentation currently available on devices: high spectral resolution similar an crystal spectrometer broad coverage sufficient measure impurity species from Be W. As a proof-of-principle experiment, NASA-built microcalorimeter...
A novel Motional Stark Effect spectroscopy system has been designed for application at the DIII-D tokamak. The is optimized studies of poloidal and toroidal magnetic field in plasma pedestal region with frame rates up to 10 kHz. Light from an existing high-photon-throughput collection lens analyzed using four single-channel f/2.8 Czerny-Turner spectrometers that use custom-made systems instead mirrors. Each spectrometer two separate outgoing legs operated a positive grating order, which...
The Soft X-Ray (SXR) tomography system on the Madison Symmetric Torus uses four cameras to determine emissivity structure of plasma. This should directly correspond magnetic field; however, there is an apparent phase difference between reconstructions and field when using a cylindrical approximation. dominant rotating helical mode motion brightest line sight for each SXR camera dependent both viewing angle plasma conditions. Holding these parameters fixed, this shown be consistent over...