E. D. Fredrickson
A5083103317- Magnetic confinement fusion research
- Ionosphere and magnetosphere dynamics
- Particle accelerators and beam dynamics
- Fusion materials and technologies
- Laser-Plasma Interactions and Diagnostics
- Superconducting Materials and Applications
- Solar and Space Plasma Dynamics
- Plasma Diagnostics and Applications
- Semiconductor materials and devices
- Atomic and Subatomic Physics Research
- Nuclear reactor physics and engineering
- Nuclear Physics and Applications
- Electrostatic Discharge in Electronics
- Physics of Superconductivity and Magnetism
- Geophysics and Gravity Measurements
- Astro and Planetary Science
- Advanced Data Storage Technologies
- Atomic and Molecular Physics
- Geomagnetism and Paleomagnetism Studies
- Quantum chaos and dynamical systems
- Particle Detector Development and Performance
- Engineering Applied Research
- Radiation Effects in Electronics
- Laser-induced spectroscopy and plasma
- X-ray Spectroscopy and Fluorescence Analysis
Princeton Plasma Physics Laboratory
2015-2024
ARUP Laboratories (United States)
2022-2024
ARUP Institute for Clinical and Experimental Pathology
2024
University of Utah
2023
Princeton University
2001-2020
Lawrence Livermore National Laboratory
2006-2020
Lodestar Research Corporation (United States)
2020
Episcopal Divinity School
2013-2014
Cambridge University Press
2014
University of California, Irvine
2006-2010
A new tokamak confinement regime has been observed on the Tokamak Fusion Test Reactor (TFTR) where particle and ion thermal diffusivities drop precipitously by a factor of \ensuremath{\sim}40 to neoclassical level for particles much less than value ions in region with reversed shear. This enhanced shear mode allows central electron density rise from 0.45 \ifmmode\times\else\texttimes\fi{} ${10}^{20}$ ${\mathrm{m}}^{\ensuremath{-}3}$ \ensuremath{\sim}1.2 ${T}_{i}\ensuremath{\sim}24$ keV...
A detailed comparison is made between the tearing-type modes observed in TFTR supershot plasmas and nonlinear, neoclassical pressure-gradient--driven tearing mode theory. Good agreement found on nonlinear evolution of single helicity magnetic islands $(m/n\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}3/2$, $4/3$, or $5/4$, where $m$ $n$ are poloidal toroidal numbers, respectively). The saturation these requires ${\ensuremath{\Delta}}^{\ensuremath{'}}<0$ (where...
Deuterium neutral beams with energies up to 110 keV were injected into TFTR (Tokamak Fusion Test Reactor) plasmas at low magnetic field such that the beam injection velocities comparable Alfv\'en velocity. Excitation of toroidal eigenmodes was observed by Mirnov coils and emission spectroscopy.
Abstract The objectives of NSTX-U research are to reinforce the advantages STs while addressing challenges. To extend confinement physics low- A , high beta plasmas lower collisionality levels, understanding transport mechanisms that set performance and pedestal profiles is being advanced through gyrokinetic simulations, reduced model development, comparison NSTX experiment, as well improved simulation RF heating. develop stable non-inductive scenarios needed for steady-state operation,...
Simultaneous profile measurements of the toroidal rotation speed and ion temperature during unbalanced neutral beam injection in Tokamak Fusion Test Reactor show that momentum thermal diffusivities are comparable magnitude (${\mathrm{\ensuremath{\chi}}}_{\mathrm{\ensuremath{\varphi}}}$\ensuremath{\approxeq}1.5${\mathrm{\ensuremath{\chi}}}_{\mathrm{i}}$) vary similarly with plasma current minor radius. The correlation ${\mathrm{\ensuremath{\chi}}}_{\mathrm{\ensuremath{\varphi}}}$...
Research in NSTX has been conducted to establish spherical torus plasmas be used for high β, auxiliary heated experiments. This device a major radius R0 = 0.86 m and midplane halfwidth of 0.7 m. It operated with toroidal magnetic field B0 ⩽ 0.3 T Ip 1.0 MA. The evolution the plasma equilibrium is analysed between discharges an automated version EFIT code. Limiter, double null lower single diverted configurations have sustained several energy confinement times. stored reached 92 kJ (βt 17.8%)...
Compact optimized stellarators offer novel solutions for confining high-β plasmas and developing magnetic confinement fusion. The three-dimensional plasma shape can be designed to enhance the magnetohydrodynamic (MHD) stability without feedback or nearby conducting structures provide drift-orbit similar tokamaks. These configurations possibility of combining steady-state low-recirculating power, external control, disruption resilience previous with low aspect ratio, high β limit, good...
Wall conditioning in the Tokamak Fusion Test Reactor (TFTR) [K. M. McGuire et al., Phys. Plasmas 2, 2176 (1995)] by injection of lithium pellets into plasma has resulted large improvements deuterium–tritium fusion power production (up to 10.7 MW), Lawson triple product 1021 m−3 s keV), and energy confinement time 330 ms). The maximum current for access high-performance supershots been increased from 1.9 2.7 MA, leading stable operation at stored values greater than 5 MJ. amount on limiter...
A transport code (TRANSP) is used to simulate future deuterium-tritium (DT) experiments in TFTR.The simulations are derived from 14 TFTR DD discharges, and the modelling of one supershot discussed detail indicate degree accuracy TRANSP modelling.Fusion energy yields 01 particle parameters calculated, including profiles slowing down time, average energy, AlfvBn speed frequency.Two types simulation discussed.The main emphasis on DT equivalent, where an equal mix D T substituted for initial...
Using newly developed techniques and improved diagnostics, rotating wall-stabilized discharges have been maintained in the DIII-D tokamak for 30 characteristic resistive wall decay times---significantly longer than was previously achieved. The terminating mode has directly identified using internal fluctuation its correlation with slowdown plasma rotation is established.
Off-axis sawteeth are often observed in reversed magnetic shear plasmas when the minimum safety factor $q$ is near or below 2. Fluctuations with $m/n\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}2/1$ ( $m$ and $n$ poloidal toroidal mode numbers) appear before after crashes. Detailed comparison has been made between measured ${T}_{e}$ profile evaluation during crash a nonlinear numerical magnetohydrodynamics simulation. The good agreement observation simulation indicates that off-axis...
Peak fusion power production of 6.2\ifmmode\pm\else\textpm\fi{}0.4 MW has been achieved in TFTR plasmas heated by deuterium and tritium neutral beams at a total 29.5 MW. These have an inferred central alpha particle density 1.2\ifmmode\times\else\texttimes\fi{}${10}^{17}$ ${\mathrm{m}}^{\mathrm{\ensuremath{-}}3}$ without the appearance either disruptive magnetohydrodynamics events or detectable changes Alfv\'en wave activity. The measured loss rate energetic particles agreed with...
Recent experiments (Synakowski et al 2004 Nucl. Fusion 43 1648, Lloyd Plasma Phys. Control. 46 B477) on the Spherical Tokamak (or Torus, ST) (Peng 2000 Plasmas 7 1681) have discovered robust plasma conditions, easing shaping, stability limits, energy confinement, self-driven current and sustainment. This progress has encouraged an update of conditions engineering a Component Test Facility (CTF), (Cheng 1998 Eng. Des. 38 219) which is very valuable step in development practical fusion energy....
The time-scales for sawtooth repetition and heat pulse propagation are much longer (tens of milliseconds) in the large tokamak TFTR than previous, smaller tokamaks. This extended time-scale, coupled with more detailed diagnostics, has led us to revisit analysis as a method determine electron diffusivity χe plasma. A combination analytic computer solutions diffusion equation is used clarify previous work develop new methods determining χe. Direct comparison predicted pulses soft-X-ray ECE...
Remarkable progress has been made in diagnosing energetic particle instabilities on presentday machines and establishing a theoretical framework for describing them.This overview describes the much improved diagnostics of Alfvén modelling tools developed world-wide, discusses interpreting observed phenomena.A multi-machine comparison is presented giving information performance both different plasma conditions outlining expectations ITER based our present knowledge.
The numerical methods used in the full particle-orbit following SPIRAL code are described and a number of physics studies performed with presented to illustrate its capabilities. is test-particle powerful tool interpret plan fast-ion experiments tokamaks. Gyro-orbit effects important for fast ions low-field machines such as NSTX lesser extent DIII-D. A interlaced between description Results on heat loads generated by localized error-field DIII-D wall compared measurements. enhanced Triton...
A proof of principle magnetic feedback stabilization experiment has been carried out to suppress the resistive wall mode (RWM), a branch ideal magnetohydrodynamic (MHD) kink under influence stabilizing wall, on DIII-D tokamak device [Plasma Phys. Controlled Fusion Research (International Atomic Energy Agency, Vienna, 1986), p. 159; Plasmas 1, 1415 (1994)]. The RWM was successfully suppressed and high beta duration above no-wall limit extended more than 50 times flux diffusion time. It...
Alpha-particle-driven toroidal Alfvén eigenmodes (TAEs) have been observed for the first time in deuterium-tritium (D-T) plasmas on tokamak fusion test reactor (TFTR). These modes are 100–200 ms following end of neutral beam injection with reduced central magnetic shear and elevated safety factor [q0>1]. Mode activity is localized to region discharge r/a<0.5 fluctuation level B̃⊥/B∥∼10−5 mode numbers range n=2–4, consistent theoretical calculations α-TAE stability TFTR.Received 11 November...
A wide variety of fast ion driven instabilities are excited during neutral beam injection (NBI) in the National Spherical Torus Experiment (NSTX) [Nucl. Fusion 40, 557 (2000)] due to large ratio velocity Alfvén velocity, Vfast∕VAlfvén, and high beta. The Vfast∕VAlfvén ITER 39, 2137 (1999)] NSTX is comparable. modes can be divided into three categories: chirping energetic particle (EPM) frequency range 0 120kHz, toroidal eigenmodes (TAE) with a 50kHz 200kHz, compressional global (CAE GAE,...
After many years of fusion research, the conditions needed for a D–T reactor have been approached on Tokamak Fusion Test Reactor (TFTR) [Fusion Technol. 21, 1324 (1992)]. For first time unique phenomena present in plasma are now being studied laboratory plasma. The magnetic experiments to study plasmas using nearly equal concentrations deuterium and tritium carried out TFTR. At maximum power 10.7 MW, 39.5 MW neutral-beam heating, supershot discharge 6.7 high-βp following current rampdown....
Supershots in TFTR often suffer a performance deterioration characterized by gradual decrease of the DD fusion neutron yield and plasma stored energy after several hundred milliseconds auxiliary heating. The correlation between this development low m (the poloidal mode number), n toroidal number) MHD modes is studied through shot-to-shot comparisons statistical data analyses. A good observed appearance strong 3/2 4/3 macroscopic modes. magnetic island structures are using Mirnov ECE...
Magnetic diagnostics are essential for the operation and understanding of a magnetic fusion device. data used in real time to measure control current, shape, position discharge; thermal energy plasma; confining field; currents magnet coils. Equilibrium reconstructions based on yield geometry plasma, providing coordinates interpretation all other diagnostic measurements. measurements also provide input analysis feedback magnetohydrodynamic (MHD) instabilities. This review focuses inductive...
Research on the National Spherical Torus Experiment, NSTX, targets physics understanding needed for extrapolation to a steady-state ST Fusion Nuclear Science Facility, pilot plant, or DEMO. The unique operational space is leveraged test theories next-step tokamak operation, including ITER. Present research also examines implications coming device upgrade, NSTX-U. An energy confinement time, τE, scaling unified varied wall conditions exhibits strong improvement of BTτE with decreased electron...
Abstract An increased total energy was correlated with the addition of tritium were observed in supershots [1] during TFTR DT campaign [2] This regime had strikingly high, centrally peaked ion and electron temperatures, largest neutron emission rates TFTR. paper presents a study origin this increase stored energy. &#xD;&#xD;Twenty-six recently reanalyzed TRANSP plasma analysis code.Previous simulations did not accurately match measured magnitude time evolutions rates. mismatch is...