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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 847 records · Page 47
All sourcesNASA NTRSDOE OSTI
DOE OSTI2012

Pulse-discharge plasmas for plasma-accelerator applications

For particle-beam-driven plasma wakefield accelerators, a long and fully-ionized plasma is desirable. We describe an experiment at UCLA to develop a prototype of such plasma using a pulsed-current discharge. Scaling of the plasma density with glass-tube diameter and with discharge-circuit parameters is currently underway. We have found that 4 Torr of Argon can be fully ionized to a density of about 1.3 Multiplication-Sign 10{sup 17} cm{sup -3} when the current density in the 1 inch diameter, 1.2 meter-long tube is around 2 kA/cm{sup 2}, at least at one point along the discharge. The homogeneity of the plasma density in the longitudinal direction is crucial to prevent slippage of the driven plasma structures with the particles. Equally important are the transverse gradients since any dipole asymmetry in the transverse direction can lead to 'steering' of the particle beam. The longitudinal and transverse gradients may be a function of time into the discharge, the shape of the electrodes, the tube size, and the fractional ionization for a given fill pressure. These issues are currently under investigation.

43 PARTICLE ACCELERATORS↗
DOE OSTI2012

Production and acceleration of ion beams by laser ablation

In this work, we present a new pulsed laser ablation technique to obtain energetic ion beams. The accelerator we made is a compact device able to extract and accelerate the ionic components of plasma up to 160 keV per charge state. It is composed by a generating chamber containing an expansion chamber used like first electrode. Next, a second electrode connected to ground and a third electrode connected to negative voltage are used. The third electrode is used also as Faraday cup. By the analysis of the ion signals we studied the plume parameters such as TOF accelerated signals, charge state, and divergence.

43 PARTICLE ACCELERATORS↗
DOE OSTI2014

Observation of multi-scale turbulence and non-local transport in LHD plasmas

We have studied two types of spatio-temporal turbulence dynamics in plasmas in the Large Helical Device, based on turbulence measurements with high spatial and temporal resolution. Applying conditional ensemble-averaging to a plasma with Edge-Localized Modes (ELMs), fast radial inward propagation of a micro-scale turbulence front is observed just after ELM event, and the propagation speed is evaluated as ∼100 m/s. A self-organized radial electric field structure is observed in an electrode biasing experiment, and it is found to realize a multi-valued state. The curvature of the radial electric field is found to play an important role for turbulence reduction.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
NASA NTRS2009

Pulsed Plasma Accelerator Modeling

This report presents the main results of the modeling task of the PPA project. The objective of this task is to make major progress towards developing a new computational tool with new capabilities for simulating cylindrically symmetric 2.5 dimensional (2.5 D) PPA's. This tool may be used for designing, optimizing, and understanding the operation of PPA s and other pulsed power devices. The foundation for this task is the 2-D, cylindrically symmetric, magnetohydrodynamic (MHD) code PCAPPS (Princeton Code for Advanced Plasma Propulsion Simulation). PCAPPS was originally developed by Sankaran (2001, 2005) to model Lithium Lorentz Force Accelerators (LLFA's), which are electrode based devices, and are typically operated in continuous magnetic field to the model, and implementing a first principles, self-consistent algorithm to couple the plasma and power circuit that drives the plasma dynamics.

Goodman, M.↗
DOE OSTI2016

Time-delayed transition of normal-to-abnormal glow in pin-to-water discharge

Time-delayed transition of normal-to-abnormal glow was investigated in discharge between spoke-like pins and ultrapure water by applying AC-driven power at a frequency of 14.3 kHz at atmospheric pressure. The normal-to-abnormal transition can be recognized from the slope changes of current density, gas temperature, electrode temperature, and OH density. The slope changes took place in tens of minutes rather than just after discharge, in other words, the transition was delayed. The time-delay of the transition was caused by the interaction between the plasma and water. The plasma affected water properties, and then the water affected plasma properties.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2015

Negative ion production in the RF multiaperture surface-plasma source

The experiments on negative hydrogen ion beam production in a multi-aperture long-pulse surface-plasma source are described. H- ions are produced on the surface of a plasma grid covered by cesium and illuminated by fast plasma particles. The source uses a radio-frequency driver to generate plasma. A composite magnet system made of external permanent magnets confines and filters electrons in the plasma region, and deflects them in the extraction area. A multiaperture, multi-electrode ion optical system is used for beam formation. The electrode heating and cooling during long pulses is accomplished by circulating a heat transfer fluid through channels drilled in the electrodes bodies. H- ions extraction through a single aperture and 21 apertures was performed and studied. A stable H- beam with the current up to 0.7 A, energy up to 74 kV, and pulse duration up to 7 s was routinely obtained.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
NASA NTRS2003

Phenomenological Model of Current Sheet Canting in Pulsed Electromagnetic Accelerators

The phenomenon of current sheet canting in pulsed electromagnetic accelerators is the departure of the plasma sheet (that carries the current) from a plane that is perpendicular to the electrodes to one that is skewed, or tipped. Review of pulsed electromagnetic accelerator literature reveals that current sheet canting is a ubiquitous phenomenon - occurring in all of the standard accelerator geometries. Developing an understanding of current sheet canting is important because it can detract from the propellant sweeping capabilities of current sheets and, hence, negatively impact the overall efficiency of pulsed electromagnetic accelerators. In the present study, it is postulated that depletion of plasma near the anode, which results from axial density gradient induced diamagnetic drift, occurs during the early stages of the discharge, creating a density gradient normal to the anode, with a characteristic length on the order of the ion skin depth. Rapid penetration of the magnetic field through this region ensues, due to the Hall effect, leading to a canted current front ahead of the initial current conduction channel. In this model, once the current sheet reaches appreciable speeds, entrainment of stationary propellant replenishes plasma in the anode region, inhibiting further Hall-convective transport of the magnetic field; however, the previously established tilted current sheet remains at a fairly constant canting angle for the remainder of the discharge cycle, exerting a transverse J x B force which drives plasma toward the cathode and accumulates it there. This proposed sequence of events has been incorporated into a phenomenological model. The model predicts that canting can be reduced by using low atomic mass propellants with high propellant loading number density; the model results are shown to give qualitative agreement with experimentally measured canting angle mass dependence trends.

Markusic, Thomas↗
DOE OSTI2017

Increasing plasma parameters using sheared flow stabilization of a Z-pinch

The ZaP and ZaP-HD Flow Z-pinch experiments at the University of Washington have successfully demonstrated that sheared plasma flows can be used as a stabilization mechanism over a range of parameters that has not previously been accessible to long-lived Z-pinch configurations. The stabilization is effective even when the plasma column is compressed to small radii, producing predicted increases in magnetic field and electron temperature. The flow shear value, extent, and duration are shown to be consistent with theoretical models of the plasma viscosity, which places a design constraint on the maximum axial length of a sheared flow stabilized Z-pinch. Measurements of the magnetic field topology indicate simultaneous azimuthal symmetry and axial uniformity along the entire 100 cm length of the Z-pinch plasma. Separate control of plasma acceleration and compression has increased the accessible plasma parameters and has generated stable plasmas with radii of 0.3 cm, as measured with a high resolution digital holographic interferometer. Compressing the plasma with higher pinch currents has produced high magnetic fields (8.5 T) and electron temperatures (1 keV) with an electron density of 2×10 17 cm -3 , while maintaining plasma stability for many Alfvén times (approximately 50 μs). Thus, the results suggest that sheared flow stabilization can be applied to extend Z-pinch plasma parameters to high energy densities.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2012

Cyclic powder formation during pulsed injection of hexamethyldisiloxane in an axially asymmetric radiofrequency argon discharge

A new approach of periodic production of dusty plasma consisting of pulsed injection of hexamethyldisiloxane (HMDSO) in argon axially asymmetric radiofrequency (RF) discharge was investigated in this work. The range of plasma operating conditions in which this dusty plasma can exist was closely examined. The obtained results clearly show that a net periodicity in the formation/disappearance of dust particles in the plasma can be maintained on a very large scale of discharge duration. The significance of discharge axial asymmetry to the dust particles behaviour in the plasma is revealed by the development of an asymmetric in shape void shifted towards the powered RF electrode. The key role of the reactive gas and its pulsed injection on each stage of the oscillating process of formation/disappearance of dust particles is disclosed by optical and electrical measurements. It is shown that the period of dusty plasma formation/disappearance is inversely related to the HMDSO injection time. Moreover, the impact of time injection over short period (5 s) is examined. It indicates the conflicting role played by the HMDSO on the reduction of dusty plasma during the reactive gas injection and the reappearance of particles in the plasma during the time off. The electronegative behavior of the plasma in the presence of negatively charged particles seems to explain the energetic modifications in the discharge. A frequency analysis of the floating potential reveals all these cyclic processes. Particularly, in the 10-200 Hz frequency range, the presence and the evolution of dust particles in the plasma over one generation can be observed.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2021

Elucidating Hydrogen Reaction-Induced Water Desorption from Oxide-Passivated Metal Surfaces for Plasma Applications

Elucidating the mechanisms responsible for sub-microsecond desorption of water and other impurities from electrode surfaces at high heating rates is crucial for understanding pulsed power behavior. Ionization of desorbed impurities in the vacuum regions causes power or current loss; devising methods to limit such desorption during the short time scale of pulsed power is needed to improve corresponding applications. Previous molecular modeling studies have strongly suggested that, under high vacuum conditions, the amount of water impurity desorbing from oxide surfaces on metal electrodes is at a sub-monolayer level at room temperature, which appears insufficient to explain observed pulsed power energy losses at high current densities. In this work, we apply Density Functional Theory (DFT) techniques to show that hydrogen trapped inside iron metal can diffuse into hematite (α-Fe 2 O 3 ) on the metal surface, ultimately reacting with the oxide to form Fe(II) and H 2 O. The latter desorbs at elevated temperature and may explain the anomalous amount of desorbed impurity inferred from pulsed-power experiments. We also apply a suite of characterization techniques to demonstrate that when iron metal is heated to 650 °C, the dominant surface oxide component becomes α-Fe 2 O 3 . The oxide facets exposed are found to be a mixture of (0001), (10-10), and others, in agreement with the DFT models used.

74 ATOMIC AND MOLECULAR PHYSICS↗
DOE OSTI2013

Calculation of the field and current density distributions in a non-self-sustained discharge in the discharge chamber of a CO laser

Two-dimensional spatial distributions of the electric field and current density in a non-self-sustained discharge controlled by a fast electron beam were calculated in the quasineutral plasma approximation. The calculations were carried out for a gas-discharge chamber with an antistreamer electrode grid placed in parallel to the output window of the ionizer. The voltage drop near the grid surface that appears due to the inhomogeneity of the spatial distribution of the current density was calculated. The fraction of the discharge current that passes the grid and flows onto the foil separating the vacuum volume of the ionizer from the gas-discharge chamber was estimated. The dependence of the calculated values on the geometric parameters of the electrode grid and its position with respect to the output of the ionizer was analyzed.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2026

Data-Driven Modeling and Control of Systems with Plasma-Surface Interactions (Final Technical Report)

This final technical report summarizes the activities and accomplishments in the period from February 2023 thru January 2026. The objective of the proposed research is to investigate the physical mechanisms and processes underlying the formation of structures and patterns in systems with plasma-surface interactions. In the past decades, there have been extensive studies on the interaction of glow discharges, dielectric barrier discharges, and arc discharges with confining or intervening surfaces. The advancement of the understanding of these phenomena is not only of fundamental scientific interest and relevance to the knowledge of the plasma state, but also with profound implications in various technological applications. The research will integrate theoretical, computational, and experimental work within an innovative framework of data assimilation, i.e., optimally combining model predictions with measurements. The scientific merit of this research has three aspects. Firstly, it extends the studies of plasma-surface interactions to systems with insulator surfaces and multi-layer systems, while existing studies are predominantly on electrode surfaces. Secondly, it expects to develop a novel data-driven modeling approach based on data assimilation to enhance the predictive and control capabilities, which could make transformative contributions to basic plasma research. Thirdly, it will shed new light on outstanding problems related to formation of patterns interfacing plasmas. This project also aims to launch an education and outreach initiative at Texas A&M University-Kingsville, a non-R1, minority-serving institution in South Texas. The initiative is structured as a four-tier pyramid. Tier one will be a webinar series for culture and capacity building to inform broader audience in the region about the research fields of plasma science and engineering. Tier two will be the creation and offering of an upper-level undergraduate course on introductory plasma physics, which will help with the recruitment for the upper tiers. On tier three, we will engage and mentor senior design students to conduct work toward the research goal of this project. There will also be a certificate program on general plasma science for undergrad and graduate students, part of which will be lab training at Princeton University. Tier four will be the supervision and mentoring of Ph.D. students. Therefore, this project will systematically expand the talent pipeline, broaden participation from communities historically and geographically underrepresented in DOE SC research portfolio, significantly improve the research and education capacity at the PI’s institution, and contribute to developing a diverse workforce in plasma science and engineering.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2011

Production of a high brightness H{sup -} beam by charge exchange of a hydrogen atom beam in a sodium jet

Production of H{sup -} beams for applications in accelerators via charge exchange of a high brightness hydrogen neutral beam in a sodium jet cell is experimentally studied in a joint experiment by the Brookhaven National Laboratory (BNL) and the Budker Institute of Nuclear Physcis (BINP). In the experiment, a hydrogen atomic beam with an energy 3-6 keV, an equivalent current up to 5 A and a pulse duration 200 microseconds is used. Initial results demonstrate that an H{sup -} beam with a current 36 mA, an energy 5 keV and {approx}0.15 cm{center_dot}mrad normalized emittance was obtained. The recirculating sodium jet target with an entrance aperture 2 cm, which was developed for the BNL optically pumped polarized ion source, is used in the experiment. To increase the H{sup -} beam current, geometric focusing of the hydrogen neutral beam will be used in the future experiments. In addition, the effects of H{sup -} beam space-charge and sodium-jet stability will be studied to determine the basic limitations of this approach. The atomic beam is produced by charge exchange of a proton beam in a pulsed hydrogen target. The proton beam is formed by an ion source with a four-electrode multiaperture ion-optical system with small-size apertures. The plasma emission surface is formed by the plasma expansion from an arc plasma generator. The transverse ion temperature at the emission surface is 0.2 eV.

43 PARTICLE ACCELERATORS↗
DOE OSTI2014

Design of interferometer system for Keda Torus eXperiment using terahertz solid-state diode sources

A solid-state source based terahertz (THz) interferometer diagnostic system has been designed and characterized for the Keda Torus eXperiment (KTX). The THz interferometer utilizes the planar diodes based frequency multiplier (X48) to provide the probing beam at fixed frequency 0.650 THz, and local oscillator is provided by an independent solid-state diode source with tunable frequency (0.650 THz +/− 10 MHz). Both solid-state sources have approximately 1 mW power. The planar-diode mixers optimized for high sensitivity, ∼750 mV/mW, are used in the heterodyne detection system, which permits multichannel interferometer on KTX with a low phase noise. A sensitivity of {sub min} = 4.5 × 10{sup 16} m{sup −2} and a temporal resolution of 0.2 μs have been achieved during the initial bench test.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
NASA NTRSDate not supplied

Indirect Magnetic Measurements on the Aerodynamic Heating Facility (AHF)

The arc jet complex at NASA Ames Research Center (ARC) investigates various thermal protection systems (TPS) and their performance in high enthalpy flow environments to improve heat shields used in atmospheric entry. The arc jet operates by inducing an arc between two electrodes and passing the heated gas through a supersonic nozzle. The arc plasma is typically a partially ionized air mixture at low temperature (< 2 eV) but operates for long periods of time (up to 30 min) at high power (< 60 MW). However, simulations using the in-house ARC Heater Simulator (ARCHeS) code predict that the arc is still unstable to MHD instabilities, primarily the kink instability, which limit the operational envelope of the facility [1]. Consequently, it is important to better characterize these instabilities to improve facility stability and extend operational ranges. Due to the high enthalpy and long timescales (i.e., minutes) arc diagnostics must be non-invasive (i.e., optical or magnetic). This work will cover the development of tri-axial magnetic hall sensors for arc jet instabilities and subsequent 3D characterization of arc motion. The latest results describing the kink instability amplitude, frequency and wavelength will be presented and represent the first measurements of this instability in a NASA arc jet facility. References: [1] Meurisse, J. (2018). 3D Unsteady Model of Arc Heater Plasma Flow Using the ARC Heater Simulator (ARCHeS), APS Gaseous Electronics Conference, 2018: APS.

Sebastian Vicente Colom↗
DOE OSTI2012

Device for generation of pulsed corona discharge

The invention is a method and system for the generation of high voltage, pulsed, periodic corona discharges capable of being used in the presence of conductive liquid droplets. The method and system can be used, for example, in different devices for cleaning of gaseous or liquid media using pulsed corona discharge. Specially designed electrodes and an inductor increase the efficiency of the system, permit the plasma chemical oxidation of detrimental impurities, and increase the range of stable discharge operations in the presence of droplets of water or other conductive liquids in the discharge chamber.

47 OTHER INSTRUMENTATION↗
DOE OSTI2016

Non-Maxwellian to Maxwellian transitions of atmospheric microplasmas at microwave frequencies

Particle-in-cell/Monte Carlo simulations and numerical analysis of a single particle motion are performed for atmospheric He microplasmas at microwave frequencies to determine the characteristics of non-Maxwellian to Maxwellian transition. The left and the right regimes of Paschen curve, divided by this transition, reveal that the transition frequencies depend on the gap of electrodes and the neutral gas pressure to follow scaling laws for a new extended Paschen law. The fluid models are reasonable at the right-side regime of Paschen breakdown areas, but not on the left side, which is highly kinetic for electrons. The plasmas driven by weaker electric fields of high enough frequencies at the right-side Paschen regime breed more energetic electrons.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗