A5057868914- Magnetic confinement fusion research
- Ionosphere and magnetosphere dynamics
- Planetary Science and Exploration
- Particle accelerators and beam dynamics
- Superconducting Materials and Applications
- Astro and Planetary Science
- Plasma Diagnostics and Applications
- Solar and Space Plasma Dynamics
- Fusion materials and technologies
- Laser-Plasma Interactions and Diagnostics
- Atomic and Subatomic Physics Research
- Laser-induced spectroscopy and plasma
- Nuclear Physics and Applications
- Particle Dynamics in Fluid Flows
- Space Exploration and Technology
- Gyrotron and Vacuum Electronics Research
- Gas Dynamics and Kinetic Theory
- Meteorological Phenomena and Simulations
- Particle Accelerators and Free-Electron Lasers
- Soil Moisture and Remote Sensing
- Atmospheric aerosols and clouds
- Fluid Dynamics and Turbulent Flows
- Spacecraft and Cryogenic Technologies
- Physics of Superconductivity and Magnetism
- Particle Detector Development and Performance
Laboratory for Atmospheric and Space Physics
2011-2023
University of Colorado Boulder
2013-2023
University of Colorado System
2005-2023
Solar System Exploration Research Virtual Institute
2011-2022
Saint Mary's College of California
2017
University of California, San Diego
2006-2013
Princeton Plasma Physics Laboratory
1997-2010
University of Warwick
2010
Princeton University
1997-2006
Higashihiroshima Medical Center
2006
High resolution (temporal and spatial), two-dimensional images of electron temperature fluctuations during sawtooth oscillations were employed to study the crash process heat transfer in magnetically confined toroidal plasmas. The combination kink local pressure driven instabilities leads a small poloidally localized puncture magnetic surface at both low high field sides poloidal plane. This observation closely resembles ``fingering event'' ballooning mode model with high-$m$ only predicted side.
The newly installed electron cyclotron emission imaging diagnostic on ASDEX Upgrade provides measurements of the 2D temperature dynamics with high spatial and temporal resolution. An overview technical experimental properties system is presented. These are illustrated by edge localized mode reversed shear Alfvén eigenmode, showing both advantage having a two-dimensional (2D) measurement, as well some limitations measurements. Furthermore, application singular value decomposition powerful...
A new electron cyclotron emission imaging diagnostic has been commissioned on the DIII-D tokamak. Dual detector arrays provide simultaneous two-dimensional images of Te fluctuations over radially distinct and reconfigurable regions, each with both vertical radial zoom capability. total 320 (20 vertical×16 radial) channels are available. First data from this demonstrate acquisition coherent temperature as low 0.1% excellent clarity spatial resolution. Details features capabilities presented.
A hypervelocity dust accelerator for studying micrometeorite impacts has been constructed at the Colorado Center Lunar Dust and Atmospheric Studies (CCLDAS) University of Colorado. Based on Max-Planck-Institüt für Kernphysik (MPI-K) accelerator, this is capable emitting single particles a specific mass velocity selected by user. The consists 3 MV Pelletron generator with source, four image charge pickup detectors, two interchangeable target chambers: large high-vacuum test bed an ultra-high...
This paper describes the first observations in National Spherical Torus Experiment (NSTX) [S. M. Kaye et al., Phys. Plasmas 8, 1977 (2001)] of “quiet periods” edge turbulence preceding low-to-high (L-H) mode transition, as diagnosed by gas puff imaging (GPI) diagnostic near outer midplane separatrix. During these quiet periods GPI Dα light emission pattern was transiently similar to that seen during H-mode, i.e., with a relatively small fraction located outside These had frequency ∼3 kHz for...
Investigating the dynamical and physical properties of cosmic dust can reveal a great deal information about both its many sources. Over recent years, several spacecraft (e.g., Cassini, Stardust, Galileo, Ulysses) have successfully characterised interstellar, interplanetary, circumplanetary using variety techniques, including in situ analyses sample return. Charge, mass, velocity measurements are performed either directly (induced charge signals) or indirectly (mass from impact ionisation...
This paper describes the range of variations in edge and SOL turbulence observed using a gas puff imaging (GPI) diagnostic NSTX discharges. The database consists 140 shots including Ohmic, L-mode, H-mode plasmas measured during steady-state conditions (e.g. without ELMs). Turbulence quantities were evaluated both cross-correlation analysis blob tracking. Relative fluctuation levels varied from –1.0, correlation times –40 μs, lengths –10 cm, velocities km s−1 outwards. These with respect to...
Significant advances in microwave and millimeter wave technology over the past decade have enabled development of a new generation imaging diagnostics for current envisioned magnetic fusion devices. Prominent among these are electron cyclotron emission imaging, phase interferometers, scattering, reflectometer systems Te ne fluctuations (both turbulent coherent) profiles (including transport barriers) on toroidal devices such as tokamaks, spherical tori, stellarators. The diagnostic is...
Diagnostic systems for fluctuation measurements in plasmas are, of necessity, evolving from simple one-dimensional (1D) to multidimensional due the complexity magnetohydrodynamics (MHD) and turbulence physics as illustrated by advanced numerical simulations. Using recent significant advancements millimeter wave imaging technology, microwave reflectometry (MIR) electron cyclotron emission (ECEI), simultaneously measuring density temperature fluctuations, have been developed Toroidal...
High temporal and spatial resolution two-dimensional (2D) images of electron temperature fluctuations were employed to study the sawtooth oscillation in Toroidal Experiment for Technically Oriented Research tokamak plasmas. The 2D are directly compared with expected patterns plasma pressure (or temperature) from various theoretical models. observed experimental only partially agreement each model: image initial reconnection process is similar that ballooning mode model. intermediate final...
H-mode operation plays a crucial role in National Spherical Torus Experiment (NSTX) research, allowing higher beta limits due to reduced plasma pressure peaking, and long pulse high bootstrap current fraction. Here, new results are presented the areas of edge localized modes (ELMs), pedestal physics power threshold studies. ELMs several types as reported by aspect ratio tokamaks have been observed: (1) large, Type I ELMs, (2) intermediate-sized III (3) tiny ELMs. Many performance discharges...
In this paper we compare the structure and motion of edge turbulence observed in L-mode vs. H-mode plasmas National Spherical Torus Experiment (NSTX) [M. Ono, M. G. Bell, R. E. Bell et al., Plasma Phys. Controlled Fusion 45, A335 (2003)]. The radial poloidal correlation lengths are not significantly different between cases examined. velocity fluctuations lower profiles somewhat flatter compared with plasmas. These results similar measurements Alcator C-Mod [E. Marmar, B. Bai, L. Boivin Nucl....
The major objective of the National Spherical Torus Experiment (NSTX) is to understand basic toroidal confinement physics at low aspect ratio and high βT in order advance spherical torus (ST) concept. In do this, NSTX utilizes up 7.5 MW neutral beam injection, 6 harmonic fast waves (HHFWs), it operates with plasma currents 1.5 MA elongations 2.6 a field 0.45 T. New facility, diagnostic modelling capabilities developed over past two years have enabled research team make significant progress...
Understanding the behavior of fluctuations in magnetically confined plasmas is essential to advancement turbulence-based transport physics. Though microwave reflectometry has proven be an extremely useful and sensitive tool for measuring small density some circumstances, this technique been shown have limited viability large amplitude, high kθ and/or core measurements. To end, a new instrument based on two-dimensional imaging developed measure over extended plasma region TEXTOR tokamak. This...
A synthetic gas puff imaging (GPI) diagnostic has been added to the scrape-off layer turbulence (SOLT) simulation code, enabling comparisons with GPI data from National Spherical Torus Experiment (NSTX) [M. Ono et al., Nucl. Fusion 40, 557 (2000)]. The edge and are modeled in radial poloidal (bidirectional) dimensions of outboard midplane region NSTX. low-confinement mode discharge is simulated by choosing reference parameters, including density temperature profiles, be consistent those shot...
Abstract The interpretation of meteor radar observations has remained an open problem for decades. One the most critical parameters to establish size incoming meteoroid from echoes is ionization coefficient, β , which still remains poorly known. Here we report on new experiments simulate micrometeoroid ablation in laboratory conditions measure iron particles impacting N 2 air, CO and He gases. This data set compared previous where find agreement except air impacts > 30 km/s. We calibrate...
To study the mechanism of anomalous transport in tokamaks requires use sophisticated diagnostic tools for measurement short-scale turbulent fluctuations. In this article, we describe an attempt at developing a technique capable providing comprehensive description plasma fluctuations with k⊥ρi<1, such as those driven by ion temperature gradient mode tokamaks. The proposed method is based on microwave reflectometry, and stems from series numerical calculations showing that spatial...
The National Spherical Torus Experiment (NSTX) has made considerable progress in advancing the scientific understanding of high performance long-pulse plasmas needed for future spherical torus (ST) devices and ITER.Plasma durations up to 1.6 s (five current redistribution times) have been achieved at plasma currents 0.7 MA with non-inductive fractions above 65% while simultaneously achieving β T N values 17% 5.7 (%m -1 ), respectively.A newly available motional Stark effect diagnostic...
Time-resolved two-dimensional (2D) velocity maps have been derived for fluctuation measurements in the edge plasma of National Spherical Torus Experiment (NSTX). The from time sequences 2D images recorded with gas puff imaging diagnostic. A hybrid technique combining optical flow and local pattern matching has implemented to overcome individual limitations each when used data limited temporal and/or spatial resolution. Local velocities up ∼8km∕s average poloidal ∼5km∕s are found. Results...
A new TEXTOR electron cyclotron emission imaging system has been developed and employed, providing a diagnostic with features enhanced capabilities when compared to the legacy it replaces. Optical coupling plasma completely redesigned, making use of minilens arrays for reduced optical aberration feature vertical zoom, whereby coverage is now remotely adjustable on shot-by-shot basis from 20-35 cm. Other innovations, such as implementation stacked quasioptical planar notch filters, allow be...
A gyrokinetic ion/mass-less fluid electron hybrid model as implemented in the GEM code [Y. Chen and S. E. Parker, J. Comput. Phys. 220, 837 (2007)] is used to study reverse shear Alfvén eigenmodes (RSAE) observed DIII-D, discharge #142111. This a well diagnosed case with measurement of core-localized RSAE mode structures frequency, which can be compare simulations. Simulations reproduce many features observation, including frequency up-sweeping time sweeping range. new algorithmic feature...
Spectral properties of coherent waves in an argon plasma column are examined using fluctuation data from fast imaging. Visible light ArII line emission is collected at high frame rates a high-speed digital camera. A cross-spectral phase technique allows direct visualization dominant structures as function frequency, well identification azimuthal asymmetries present the system. Experimental dispersion estimates constructed imaging alone. Drift-like identified by comparison with theoretical...
The National Spherical Torus Experiment (NSTX) is currently being upgraded to operate at twice the toroidal field and plasma current (up 1 T 2 MA), with a second, more tangentially aimed neutral beam (NB) for rotation control, allowing pulse lengths up 5 s. Recent NSTX physics analyses have addressed topics that will allow NSTX-Upgrade achieve research goals critical Fusion Nuclear Science Facility. These include producing stable, 100% non-inductive operation in high-performance plasmas,...
While microwave reflectometry has proven to be a sensitive tool for measuring electron density fluctuations in many circumstances, it also been shown have limited viability core measurements and/or conditions of strong turbulence. To this end, new instrument based on two-dimensional imaging developed measure over an extended plasma region the TEXTOR tokamak. Laboratory characterization performed using corrugated reflecting targets as approximation reflections including turbulent various...