A5034735481- Fusion materials and technologies
- Plasma Diagnostics and Applications
- Magnetic confinement fusion research
- Plasma Applications and Diagnostics
- Metal and Thin Film Mechanics
- Particle accelerators and beam dynamics
- Nuclear Materials and Properties
- Muon and positron interactions and applications
- Superconducting Materials and Applications
- Semiconductor materials and devices
- Hydrogen Storage and Materials
- Copper Interconnects and Reliability
- Ionic liquids properties and applications
- Vacuum and Plasma Arcs
- Ion-surface interactions and analysis
- Advanced Chemical Physics Studies
- Additive Manufacturing and 3D Printing Technologies
- Radiation Effects in Electronics
- Electronic and Structural Properties of Oxides
- Electrohydrodynamics and Fluid Dynamics
- Catalytic Processes in Materials Science
- Electron and X-Ray Spectroscopy Techniques
- Science Education and Pedagogy
- Inorganic Fluorides and Related Compounds
- Silicone and Siloxane Chemistry
College of New Jersey
2015-2021
California Institute of Technology
2008-2020
Princeton Plasma Physics Laboratory
2014-2017
Princeton University
2015-2016
Jet Propulsion Laboratory
2009
Lehigh University
2006
The National Spherical Torus Experiment (NSTX) has undergone a major upgrade, and the NSTX Upgrade (NSTX-U) Project was completed in summer of 2015.NSTX-U first plasma subsequently achieved, diagnostic control systems have been commissioned, H-mode accessed, magnetic error fields identified mitigated, physics research campaign carried out.During ten run weeks operation, NSTX-U surpassed record pulse-durations toroidal (TF), high-performance ~1 MA plasmas comparable to best sustained near...
The first-ever successful operation of a tokamak with large area (40% the total plasma surface area) liquid lithium wall has been achieved in Lithium Tokamak eXperiment (LTX). These results were obtained new, electron beam-based evaporation system, which can deposit coating on limiting LTX five-minute period. Preliminary analyses diamagnetic and other data for discharges operated indicate that confinement times increased by 10× compared to helium-dispersed solid coatings. Ohmic energy fresh...
High edge electron temperatures (200 eV or greater) have been measured at the wall-limited plasma boundary in Lithium Tokamak Experiment (LTX). Flat temperature profiles are a long-predicted consequence of low recycling conditions. Plasma density outer scrape-off layer is very low, 2–3 × 1017 m−3, consistent with metallic lithium boundary. Despite high temperature, core impurity content low. Zeff estimated to be ∼1.2, modest contribution (<0.1) from lithium. Experiments transient. Gas...
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,...
The effect of tungsten erosion, transport, and redeposition on the operation dispenser hollow cathodes was investigated in detailed examinations discharge cathode inserts from 8200 h 30 352 ion engine wear tests. Erosion subsequent electron emission zone at downstream end insert reduce porosity matrix, preventing flow barium interior. This inhibits interfacial reactions barium-calcium-aluminate impregnant with pores. A numerical model transport internal xenon plasma shows that required to...
In this work, measurements of electron-induced secondary electron emission (SEE) yields lithium as a function composition are presented. The results particularly relevant for magnetic fusion devices such tokamaks, field-reversed configurations, and stellarators that consider Li plasma-facing material improved plasma confinement. SEE can reduce the sheath potential at wall cool electrons edge, resulting in large power losses. These effects become significant coefficient, γe, approaches one,...
Dispenser hollow cathodes rely on a consumable supply of Ba released by BaO-CaO-Al2O3 source material in the pores tungsten matrix to maintain low work function surface. The examination cathode emitters from long duration tests shows deposits at downstream end that appear block flow interior. In addition, numerical model transport plasma indicates partial pressure insert may exceed equilibrium vapor dominant Ba-producing reaction, and it was postulated previously this would suppress loss...
The effect of barium transport on the operation dispenser hollow cathodes was investigated in numerical modeling a cathode with two different orifice sizes. Despite large differences emitter temperature, emitted electron current density, internal xenon neutral and plasma densities, size plasma-surface interaction region, geometries is qualitatively very similar. Barium produced insert flows to surface through porous structure. A buildup Ba pressure over can suppress reactions supplying Ba,...
Reactive gases such as oxygen and water vapor modify the surface morphology of BaO dispenser cathodes degrade electron emission properties. For vacuum operating at fixed temperature, current drops rapidly when adsorbs on top low work function surface. Previous experiments have shown that plasma are more resistant to poisoning can operate with O2 partial pressures one two orders magnitude higher than before onset occurs. Plasma used for electric thrusters typically operated xenon; however,...
Abstract In an effort to improve retention and persistence in the physics major, we implemented a curriculum change at our institution which enroll calculus-based Physics I course first-year majors who placed into pre-calculus level. Prior intervention, 12.5% of non-calculus-ready students were retained within major. Following 50% these have either successfully graduated with degree from or are progressing through This intervention can help address demographic disparities education, since...
Abstract The electron-induced secondary electron emission (SEE) yields of imidazolium-based ionic liquids are presented for primary beam energies between 30 and 1000 eV. These results important understanding plasma synthesis nanoparticles in discharges with an liquid electrode. Due to their low vapor pressure high conductivity, can produce metal low-pressure plasmas through reduction dissolved salts. In this work, the is exploited directly measure SEE by bombarding electrons measuring...
Hollow cathodes that operate with impurities in the xenon propellant exhibit poisoning of emitter surface, resulting a higher surface work function and increased operating temperatures. The goal this paper is to provide insight Into physical processes responsible for cathode degradation during short-duration oxygen over range discharge currents experimental results presented here show more susceptible at concentration levels, lower currents, initial insert threshold current which becomes was...
The effect of tungsten erosion, transport and redeposition on the operation dispenser hollow cathodes was investigated in detailed examinations discharge cathode inserts from an 8200 hour a 30,352 ion engine wear test. Erosion subsequent re-deposition electron emission zone at downstream end insert reduces porosity matrix, preventing ow barium interior. This inhibits interfacial reactions barium-calcium-aluminate impregnant with pores. A numerical model internal xenon plasma shows that...
Dispenser hollow cathodes rely on a consumable supply of barium released by impregnant materials in the pores tungsten matrix to maintain low work function surface. Examinations cathode inserts from long duration ion engine tests show deposits at downstream end that appear block ow interior. A numerical model transport insert plasma shows generated upstream emission zone is ionized xenon and forced back surface downstream. Barium resupply therefore occurs through gas phase. In addition,...
The effect of tungsten erosion, transport, and redeposition on the operation dispenser hollow cathodes was investigated in detailed examinations discharge cathode inserts from 8200 h 30 352 ion engine wear tests.Erosion subsequent electron emission zone at downstream end insert reduce porosity matrix, preventing flow barium interior.This inhibits interfacial reactions barium-calcium-aluminate impregnant with pores.A numerical model transport internal xenon plasma shows that required to work...
Hollow cathodes are used as the electron source for generating plasma discharge in electric thrusters. These contain porous tungsten emitters impregnated with BaO material to achieve a lower surface work function and operated xenon propellant. Reactive contaminants such oxygen gas can modify chemistry morphology of dispenser degrade emission properties. that operate reactive impurities propellant will experience higher operating temperatures, which increase evaporation materials reduce...