A5081818615- Magnetic confinement fusion research
- Fusion materials and technologies
- Superconducting Materials and Applications
- Particle accelerators and beam dynamics
- Laser-Plasma Interactions and Diagnostics
- Plasma Diagnostics and Applications
- Nuclear reactor physics and engineering
- Nuclear Materials and Properties
- Digital Holography and Microscopy
- Nuclear Physics and Applications
- Spacecraft and Cryogenic Technologies
- Semiconductor materials and devices
- Electromagnetic Launch and Propulsion Technology
- Particle Detector Development and Performance
- Rocket and propulsion systems research
- Adaptive optics and wavefront sensing
- Embedded Systems and FPGA Applications
- Laser-induced spectroscopy and plasma
- Cyclone Separators and Fluid Dynamics
- Particle Accelerators and Free-Electron Lasers
- Geophysical and Geoelectrical Methods
- Electrohydrodynamics and Fluid Dynamics
- Embedded Systems and FPGA Design
- Seismic Waves and Analysis
- Heat transfer and supercritical fluids
Oak Ridge National Laboratory
2015-2024
University of Tennessee at Knoxville
2016
Southwestern Institute of Physics
2009
High repetition rate injection of deuterium pellets from the low-field side (LFS) DIII-D tokamak is shown to trigger high-frequency edge-localized modes (ELMs) at up $12\ifmmode\times\else\texttimes\fi{}$ low natural ELM frequency in $H$-mode plasmas designed match ITER baseline configuration shape, normalized beta, and input power just above threshold. The pellet size, velocity, location were chosen limit penetration outer 10% plasma. resulting perturbations plasma density energy...
Abstract Shattered pellet injection (SPI) is one of the prime candidates for ITER disruption mitigation system because its deeper penetration and larger particle flux than massive gas (MGI) (Taylor et al 1999 Phys. Plasmas 6 1872) using deuterium (Commaux 2010 Nucl. Fusion 50 112001, Combs IEEE Trans. Plasma Sci . 38 400, Baylor 2009 49 085013). The will likely use mostly high Z species such as neon more effective thermal pumping constraints on maximum amount or helium that could be...
The technology to form and shoot high-Z cryogenic solid pellets mixed with deuterium using a gas gun that are shattered upon injection into plasma has been developed at Oak Ridge National Laboratory for mitigating disruptions. This selected as the basis baseline disruption mitigation system on ITER. development of pellet systems progressed be able accelerate large pure argon neon or without including deuterium. Impact studies have carried out shallow angles determine funnel performance in...
New rapid shutdown strategies have been recently tested in the DIII-D tokamak to mitigate runaway electrons (REs). Disruptions ITER are predicted generate multi-MeV REs that could damage machine. The RE population large tokamaks is expected be dominated by avalanche amplification which can mitigated at high density levels collisional drag. Particle injection schemes for suppression of developed and ITER-relevant scenarios: massive gas injection, shattered pellet (SPI) shell injection....
Plasma fuelling with pellet injection, pacing of edge localized modes (ELMs) by small frequent pellets and disruption mitigation gas jets or injected solid material are some the most important technological capabilities needed for successful operation ITER. Tools being developed at Oak Ridge National Laboratory that can be employed on ITER to provide necessary core ELMs disruptions. Here we present progress development technology reliable high throughput inner wall fuelling, ELM frequency...
We report on the first demonstration of dissipation fully avalanched post-disruption runaway electron (RE) beams by shattered pellet injection in DIII-D tokamak. Variation injected species shows that depends strongly mixture, while comparisons with massive gas do not show a significant difference between pellets or gas, suggesting is rapidly ablated relativistic electrons before radial penetration into beam can occur. Pure dominantly neon increases RE current through pitch-angle scattering...
Injection of massive quantities noble gases or D <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> has proven to be effective at mitigating some the deleterious effects disruptions in tokamaks. Two alternative methods that might offer advantages over present technique for gas injection are ¿shattering¿ pellets and employing close-coupled rupture disks. Laboratory testing been carried out evaluate their feasibility. For study pellets, a...
Shattered pellet injection (SPI) systems that form cryogenic pellets in a pipe-gun for of material to mitigate disruptions have been fabricated and installed use thermal mitigation runaway electron (RE) dissipation experiments on JET KSTAR. These are support disruption research ITER based an ORNL three-barrel design flexibility size selection variable composition studies. The SPI KSTAR common feature the barrels being collimated into single line enters vacuum vessel. shattered bent stainless...
Shattered pellet injection (SPI) has been selected as the baseline technology for disruption mitigation (DM) system ITER. Typical SPI utilizes cryogenic cooling to desublimate low pressure (<100 mbar) gases onto a cold zone within pipe gun barrel, forming cylindrical pellet. Pellets are dislodged from barrel and accelerated using either gas driven mechanical punch or high-pressure light-gas delivered by fast-opening valve. developed at Oak Ridge National Laboratory is currently deployed...
The injection of small deuterium pellets at high repetition rates up to 12× the natural edge localized mode (ELM) frequency has been used trigger high-frequency ELMs in otherwise low ELM H-mode discharges DIII-D tokamak [J. L. Luxon and G. Davis, Fusion Technol. 8, 441 (1985)]. resulting pellet-triggered result lower energy particle fluxes divertor than ELMs. plasma global confinement density are not strongly affected by pellet perturbations. core impurity is reduced with application...
A twin-screw extruder for the ITER pellet injection system is under development at Oak Ridge National Laboratory. The will provide a stream of solid hydrogen isotopes to secondary section, where pellets are cut and accelerated with single-stage gas gun into plasma. one-fifth scale prototype has been built produce continuous deuterium extrusion.Deuterium precooled liquefied before being introduced extruder. precooler consists copper vessel containing liquid nitrogen surrounded by filled coil....
One of the major challenges that ITER tokamak will have to face during its operations are disruptions. During last few years, it has been proven global consequences a disruption can be mitigated by injection large quantities impurities. But one aspect difficult study was possibility local effects inside torus such could damage portion device despite heat losses and generated currents remaining below design parameter. 3D MHD simulations show there is potential for toroidal asymmetries...
Disruptions are sudden unplanned terminations of tokamak plasmas that can lead to high thermal loads and runaway electrons (REs). Unmitigated disruptions in ITER predicted dissipate up 350 MJ energy generate several MA multi-MeV electrons. This intense heat energetic particle beams cause localized melting the plasma facing components. Reliable fast acting disruption mitigation (DM) techniques therefore a critical requirement for safeguard machine from damage.The proven method DM centers on...
Mitigating disruptions is essential for the longevity of future large tokamak experimental devices and reactors. Currently, shattered pellet injection (SPI) technique most effective mitigation found thus far, has been chosen baseline disruption (DM) system ITER. To optimally design SPI systems, survivability throughout pre-shatter flight resulting shatter spray must be better understood. Experimental tests low-angle single strike impacts neon argon pellets were conducted to determine minimum...
Cryogenic pellet injectors for use in fusion research have been under development at Oak Ridge National Laboratory over 30 years. The original application of the technology was to add fuel magnetically confined plasmas replace D-T ions that are consumed reactions or lost due transport out confining magnetic fields. This is still primary injection and planned implementation on ITER burning plasma experiment. More recently, there additional applications cryogenic pellets areas disruption...
A Thomson scattering (TS) diagnostic has been successfully implemented on the prototype Material Plasma Exposure eXperiment (Proto-MPEX) at Oak Ridge National Laboratory. The collects light scattered by plasma electrons and spectroscopically resolves Doppler shift imparted to velocity of electrons. spread in velocities is proportional electron temperature, while total number photons density. TS a technique used many devices measure temperature (Te) density (ne) plasma. challenging aspect...
Reliable mitigation is necessary to eliminate the detrimental effects of a disruption event in large high-current tokamaks such as ITER. To avoid serious damage plasma-facing components during thermal quench phase disruption, material injected radiate plasma energy over inner surface machine. The most promising method injection process known shattered pellet (SPI). SPI utilizes cryogenic cooling desublimate gas into barrel pipe gun form solid pellet. High-pressure or mechanical punch used...
A compact pellet injector has been built/tested at Oak Ridge National Laboratory (ORNL) for the TJ-II stellarator. The design is an upgraded version of that used ORNL installed on Madison Symmetric Torus (MST). It a four-barrel system equipped with cryogenic refrigerator in situ hydrogen formation, propellant valve acceleration (speeds ~1000 m/s), diagnostics, and injection line. On TJ-II, it will be as active diagnostic fueling. To accommodate plasma experiments planned sizes significantly...
Disruptions on ITER present challenges to handle the intense heat flux, large forces from halo currents, and potential first wall damage energetic runaway electrons. Injecting quantities of material into plasma during disruption can reduce energy increase its resistivity mitigate these effects. Assessments amount various mixtures required have been made provide collision mitigation runaway-electron conversion, which is most difficult challenge. The (~0.5 MPa·m <sup...
Shattered pellet injection (SPI) experiments on Joint European Torus (JET) are an important element in determining the physics basis for mitigating disruptions ITER. The initial design of JET SPI system included three barrels to produce pellets with diameters 4.5, 8.1, and 12.5 mm. variability speed by operating without a mechanical punch was limited led poor integrity, so removed. Fragment size distribution is function desire change resulting fragment not originally requirement. After first...
The ITER tokamak is to be fueled mainly by pellet injection and gas puffing control discharge parameters. system (PIS) will the main plasma density tool for fuelling also provides ELM pacing functionality. (GIS) wall conditioning operation, H <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> D gases NB injectors. serves critical function of disruption mitigation, including suppression runaway electrons resulting from mitigation. This paper...
The technology for producing, accelerating, and shattering large pellets (before injection into plasmas) disruption mitigation has been under development at the Oak Ridge National Laboratory several years, including a system on DIII-D that used to provide some significant experimental results. original proof-of-principle testing was carried out using pipe gun injector cooled by cryogenic refrigerator (temperatures <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML"...