Search NASA⌕ Search

SEARCH · Search NASA

Results for “HELIUM PLASMA”

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.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 397 records · Page 22
All sourcesNASA NTRSDOE OSTI
DOE OSTI2022

Deep modelling of plasma and neutral fluctuations from gas puff turbulence imaging

The role of turbulence in setting boundary plasma conditions is presently a key uncertainty in projecting to fusion energy reactors. To robustly diagnose edge turbulence, we develop and demonstrate a technique to translate brightness measurements of HeI line radiation into local plasma fluctuations via a novel integrated deep learning framework that combines neutral transport physics and collisional radiative theory for the $3^3 D - 2^3 P$ transition in atomic helium. The tenets for experimental validity are reviewed, illustrating that this turbulence analysis for ionized gases is transferable to both magnetized and unmagnetized environments with arbitrary geometries. Based upon fast camera data on the Alcator C-Mod tokamak, we present the first 2-dimensional time-dependent experimental measurements of the turbulent electron density, electron temperature, and neutral density revealing shadowing effects in a fusion plasma using a single spectral line.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
NASA NTRS1994

Convective instabilities of electromagnetic ion cyclotron waves in the outer magnetosphere

The path-integrated linear growth of electromagnetic ion cyclotron waves in the outer (L is greater than or equal to 7) magnetosphere is investigated using a realistic thermal plasma distribution with an additional anisotropic energetic ring current H(+) to provide free energy for instability. The results provide a realistic simulation of the recent Active Magneto- spheric Particle Tracer Explorers (AMPTE) observations. For conditions typical of the dayside magnetosphere, high plasma beta effects reduce the group velocity and significantly increase the spatial growth rates for left-handed polarized instabilities just below the helium gyrofrequency Omega(sub He(+)), and on the guided mode above Omega(sub He(+)) but below the cross over frequency omega(sub cr). Relatively high densities, typical of the afternoon local time sector, favor these low group velocity effects for predominantly field-aligned waves. Lower densities, typical of those found in the early morning local time sector, increase the group velocity but allow strong convective instabilities at high normalized frequencies well above Omega(sub He(+)). These waves are reflected in the magnetosphere and can exist for several equatorial transits without significant damping. They are left-handed polarized only on the first equatorial crossing and become linearly polarized for the remainder of the ray path. Consequently, these waves should be observed with basically linear polarization at all frequencies and all latitudes in the early morning local time sector. Wave growth below Omega(sub He(+)) is severely limited owing to the narrow bandwidth for instability and the small resonant path lengths. In the afternoon sector, where plasma densities can exceed 10(exp 7)/cu m, intense convective amplification is possible both above and below Omega(sub He(+)). Waves below Omega(sub He(+)) are not subject to reflection when the O(+) concentration is small and therefore should be observed with left-handed polarization near the equator and essentially linear polarization at higher latitudes. Since the He(+) concentration is usually large in the afternoon sector, guided mode waves above Omega(sub He(+)) reflect to form a background distribution with basically linear polarization. We suggest that the strong left-handed polarized emissions observed by AMPTE in the afternoon sector near the equator are probably due to strongly growing low group velocity waves at frequencies just below Omega(sub He(+)), and on the guided mode above Omega(sub He(+)).

Horne, Richard B.↗
DOE OSTI2023

Behavior and properties of helium cavities in ductile-phase-toughened tungsten irradiated with He + ions at an elevated temperature

Ductile-phase toughened tungsten (DPT W) composites have demonstrated a great potential for plasma-facing components in fusion power systems. These materials can retain the outstanding thermomechanical properties of W while significantly enhancing the fracture toughness. The DPT W composite in this study consists of W particles (88 wt.%) embedded in a ductile NiFeW (12 wt.%) solution matrix. Irradiation of the composite was performed with 90 keV He + ions to 1.0 × 10 17 He + /cm 2 at 973 K. The He cavities formed in both W and NiFeW phases are examined using convergent-beam scanning transmission electron microscopy (CB-STEM) at an atomic-level resolution. Full-range depth profiles of the He cavity diameters and number densities are analyzed. The results show that the average cavity diameter in NiFeW is ~2.7 times that in W, while the number density is an order of magnitude lower. A quantitative analysis of the He density and pressure in the cavities is also achieved using STEM electron energy loss spectroscopy (STEM-EELS) mapping. The He atoms in the cavities in NiFeW are found to be under-pressurized, while those in similar-sized cavities in W are not detectable. Further, the He energy-loss shift exhibits a linear relationship with the He density in cavities in NiFeW, with the slope comparable to that for martensitic steel.

36 MATERIALS SCIENCE↗
DOE OSTI2021

A new tri-particle backlighter for high-energy-density plasmas (invited)

A new tri-particle mono-energetic backlighter based on laser-driven implosions of DT3He gas-filled capsules has been implemented at the OMEGA laser. This platform, an extension of the original D 3 He backlighter platform, generates 9.5 MeV deuterons from the T3He reaction in addition to 14.7 and 3.0 MeV protons from the deuterium and helium-3 reactants. The monoenergetic 14.7 and 3.0 MeV protons have been used with success at OMEGA and the NIF for both radiography and stopping-power studies. There are several advantages of having a third particle to diagnose plasma conditions: an extra time-of-flight-separated radiograph and an improved ability to discern between electric and magnetic fields. In cases where the 3.0 MeV protons cannot penetrate an experiment, the benefit of the additional 9.5 MeV deuterons is magnified. This capability is well-suited for NIF experiments, where large fields and plasma densities often preclude useful 3.0 MeV proton data. The advantages are demonstrated with radiographs of OMEGA plasmas with magnetic and electric fields. Tests using backlighter-scale 420 μm diameter thin glass capsules validate the platform’s extended backlighting capability. The performance characteristics of this backlighter, such as source size and timing, are discussed.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2026

Radiation damage in tungsten under high-energy He-ion irradiation

Tungsten (W) is a primary candidate for plasma-facing components (PFCs) in fusion reactors and hybrid fission-fusion reactors. However, W suffers from severe microstructural damage under Helium (He) ion irradiation in operation conditions. Key irradiation parameters, including incident ion energy, fluence, and irradiation temperature, are known to determine the formation of He bubbles and dislocation loops, which ultimately lead to the degradation of mechanical properties, such as radiation hardening and ductile-to-brittle transition temperature (DBTT) shifts. Various strategies, for instance, interface engineering and alloying, have been developed to enhance He irradiation tolerance in W to address these challenges. Studies in the recent two decades have enhanced the understanding of the underlying mechanisms that drive defect evolution and mechanical performance degradation, thereby offering more insights into the design of more resilient W-based materials for extreme environments.

Liu, Yinghang [Purdue University]↗
NASA NTRS1982

Helium abundance enhancements in the solar wind

Evidence for a link between helium enhancements at 1 AU and transient coronal mass ejections is provided by the statistical analysis of 73 large helium abundance enhancement observations made by IMPs 6, 7 and 8 over 1972-1978. These events, in which helium abundance enhancement is greater than about 10%, are sporadic, sometimes clustered in time, occur approximately in phase with the solar cycle, and nearly 50% of them are associated with interplanetary shocks and/or geomagnetic activity sudden commencements. The plasma pattern associated with them is nevertheless independent of shock occurrence, and features high magnetic field strength, low alpha-proton velocity difference, and low proton temperature, suggesting that the enhancement is embedded in a closed, magnetically dominated structure that expands adiabatically. Evidence of an association between helium enhancement at 1 AU and type II and IV radio bursts in the corona is presented.

Borrini, G.↗
DOE OSTI2022

Deep modeling of plasma and neutral fluctuations from gas puff turbulence imaging

The role of turbulence in setting boundary plasma conditions is presently a key uncertainty in projecting to fusion energy reactors. To robustly diagnose edge turbulence, we develop and demonstrate a technique to translate brightness measurements of HeI line radiation into local plasma fluctuations via a novel integrated deep learning framework that combines neutral transport physics and collisional radiative theory for the 3 3 D - 2 3 P transition in atomic helium with unbounded correlation constraints between the electron density and temperature. The tenets for experimental validity are reviewed, illustrating that this turbulence analysis for ionized gases is transferable to both magnetized and unmagnetized environments with arbitrary geometries. Based on fast camera data on the Alcator C-Mod tokamak, we present the first two-dimensional time-dependent experimental measurements of the turbulent electron density, electron temperature, and neutral density, revealing shadowing effects in a fusion plasma using a single spectral line.

47 OTHER INSTRUMENTATION↗
DOE OSTI2020

Understanding ICF hohlraums using NIF gated laser-entrance-hole images

The newly available ns-gated laser-entrance-hole (LEH) imager on the National Ignition Facility provides routine, non-perturbative measurements of the x-ray emission from laser-heated plasmas inside the hohlraum as viewed at 19° to the hohlraum axis through one of its LEHs. Multiple images are acquired for a series of times and filter-selected x-ray energy bands within a single shot. The images provide time dependent data on phenomena including the effective radius of the LEH, the length of the gold-plasma “bubble” evolving off the interior wall surface heated by the outer beams, the evolving radius of the x-ray heated hohlraum wall, and the radius of the ablation front of the fusion capsule. Here, these measurements are explained and illustrated with sample data. These techniques are then applied to understand hohlraum behavior as a function of gas fill. For hohlraums with helium gas fill densities of 0.15 to 0.30 mg/cm 3 , synthetic images computed from simulations agree well with experimental gated LEH images when an inhibited heat transport model [Jones et al., Phys. Plasmas 24, 056312 (2017)] is used. This model can be adjusted to reproduce the expansion rate of the laser-heated plasma bubble in such a way as to improve agreement with the images. At the higher 0.6 mg/cc gas fill, the experimental images show more pronounced 3D features, resulting in slightly less good agreement with the 2D simulations.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
NASA NTRS1986

First results from Spacelab 2

Preliminary results of physical experiments carried out during the Spacelab 2 Shuttle mission are summarized. Attention is given to experiments in the fields of plasma dynamics; solar physics; high-energy astrophysics; and astronomy. Plasma experiments included an ejectable plasma diagnosics package and measurements of the passive charging of the Shuttle vehicle in the surrounding space plasma. The solar physics instrument package consisted of a solar spectral irradiance monitor; a solar optical universal polarimeter (SOUP); and a solar helium abundance high-resolution telescope and spectrograph (HRTS). Astronomical observations were performed using a scanning infrared telescope (IRT) which consisted of a highly baffled herschelian telescope and 10 detectors covering wavelengths from 2 to 120 microns. Cosmic-ray nuclei were detected and analyzed using gas Cerenkov counters and a transition radiation detector. Addition experiments included a thin film fluid dynamics payload and analysis of blood samples taken from the mission specialists. Complete data records from the experiments have now been distributed for an analysis period which will take at least a year. A table listing the Spacelab 2 experiments and their principal investigators is provided.

Urban, E. W.↗
NASA NTRS1988

A statistical study of coronal densities from X-ray line ratios of helium-like ions - Ne IX and Mg XI

Since the repair of the Solar Maximum Mission (SMM) spacecraft, the Flat Crystal Spectrometer (FCS) has recorded many high temperature spectra of helium-like ions under a wide variety of coronal conditions including active regions, long duration events, compact events, and double flares. The plasma density and temperature are derived from the ratios R and G, where R = f/i, G = (f + i)/r, and r, f, and i denote the resonance, forbidden, and intercombination line fluxes. A new method for obtaining the density and temperature for events observed with the FCS aboard SMM is presented. The results for these events are presented and compared to earlier results, and the method is evaluated based on these comparisons.

Linford, G. A.↗
DOE OSTI2021

Magnetic field effects on laser energy deposition and filamentation in magneto-inertial fusion relevant plasmas

We report on experimental measurements of how an externally imposed magnetic field affects plasma heating by kJ-class, nanosecond laser pulses. The experiments reported here took place in gas cells analogous to magnetized liner inertial fusion targets. We observed significant changes in laser propagation and energy deposition scale lengths when a 12T external magnetic field was imposed in the gas cell. We find evidence that the axial magnetic field reduces radial electron thermal transport, narrows the width of the heated plasma, and increases the axial plasma length. Reduced thermal conductivity increases radial thermal gradients. This enhances radial hydrodynamic expansion and subsequent thermal self-focusing. Our experiments and supporting 3D simulations in helium demonstrate that magnetization leads to higher thermal gradients, higher peak temperatures, more rapid blast wave development, and beam focusing with an applied field of 12T.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
NASA NTRS1972

Study of fluid mechanical helium argon ion laser

An approach to an argon ion laser based on gasdynamic techniques is presented. Improvement in efficiency and power output are achieved by eliminating high heat rejection problems and plasma confinement of the seal-off conventional lasers. The process of producing population inversion between the same energy levels, as in the conventional argon ion laser, has been divided into two phases by separating each other from the processes of ionization and subsequent excitation. Line drawings and graphs are included to amplify the theoretical presentation.

Source record↗
DOE OSTI2023

Atmospheric pressure plasma treatment of skin: penetration into hair follicles

Sterilization of skin prior to surgery is challenged by the reservoir of bacteria that resides in hair follicles. Atmospheric pressure plasma jets (APPJs) have been proposed as a method to treat and deactivate these bacteria as atmospheric plasmas are able to penetrate into structures and crevices with dimensions similar to those found in hair follicles. In this paper, we discuss results from a computational investigation of an APPJ sustained in helium flowing into ambient air, and incident onto a layered dielectric similar to human skin in which there are idealized hair follicles. We found that, depending on the location of the follicle, the bulk ionization wave (IW) incident onto the skin, or the surface IW on the skin, are able to launch IWs into the follicle. The uniformity of treatment of the follicle depends on the location of the first entry of the plasma into the follicle on the top of the skin. Typically, only one side of the follicle is treated on for a given plasma pulse, with uniform treatment resulting from rastering the plasma jet across the follicle over many pulses. Plasma treatment of the follicle is sensitive to the angle of the follicle with respect to the skin, width of the follicle pocket, conductivity of the dermis and thickness of the underlying subcutaneous fat layer, the latter due to the change in capacitance of the tissue.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2024

Verification of a Monte Carlo binary collision model for simulating elastic and inelastic collisions in particle-in-cell simulations

We present the development and verification of a Monte Carlo binary collision model for simulating elastic and inelastic collisions in particle-in-cell simulations. We apply the corrected binary collision model originally developed for charged-particles collisions to all considered scattering channels, including Coulomb collisions, elastic neutral–neutral and charged–neutral collisions, ionization, excitation, and fusion. The model's implementation is described and verified through a series of simulations, including charged- and neutral-particle thermal equilibration, slowing of electrons in warm solid-density aluminum, collisional damping of a Langmuir wave, helium gas breakdown in an applied electric field, and thermonuclear and beam–target fusion. Then, we demonstrate the model within simulations of hydrogen plasma formation in the Princeton Field-Reversed Configuration as well as of the burning of aneutronic fusion fuel p-11B. The latter includes measurement of the fusion power density in a low-density plasma and fusion production due to the stopping of a proton ignitor beam in a compressed boron target.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
NASA NTRS1974

On the distribution of He+ in the plasmasphere from observations of resonantly scattered He II 304-A radiation

The intensity of the He II 304-A radiation in the night sky was measured from a sounding rocket launched from White Sands Missile Range on June 9, 1972. The data obtained on this flight are compared with predictions of theoretical models of the He(+) altitude distribution within the plasmasphere. The observations are not consistent with an isothermal equilibrium model of the helium ion in the plasmasphere, confirming earlier results. The data are best fit by a diffussive equilibrium model of exospheric He(+) having a plasma temperature gradient of 0.5 K per km and a number density at 1600 km of 200,000 He(+) ions per cu cm. In this model the ion densities are calculated without allowance for thermal diffusion. A similar model that allows for thermal diffusion and that has a He(+) number density at 1600 km of 1500 per cu cm and a temperature gradient of 1.2 K per km yields a less satisfactory fit to the observations but is more consistent with in situ satellite observations.

Paresce, F.↗
NASA NTRS1992

Gas Contamination In Plasma-Arc-Welded Aluminum

Document describes experimental investigation on visible and tactile effects of gaseous contaminants in variable-polarity plasma arc (VPPA) welding of 2219 T-87 aluminum alloy. Contaminant gases (nitrogen, methane, oxygen, and hydrogen) introduced in argon arc and in helium shield gas in various controlled concentrations. Report represents results of experiments in form of photographs of fronts, backs, polished cross sections, and etched cross sections of welds made with various contaminants at various concentrations. Provides detailed discussion of conditions under which welds made.

Mcclure, John C.↗
NASA NTRS1981

Solar wind helium and hydrogen structure near the heliospheric current sheet - A signal of coronal streamers at 1 AU

Solar wind flow properties associated with very low helium to hydrogen abundance ratios have been observed with Los Alamos instruments on IMP 6, 7, and 8 during 1971-1978. A characteristic pattern has been discovered consisting of correlated interplanetary field reversals, high plasma density, low and nearly identical H(+) and He(2+) bulk velocities, low H(+) and He(2+) kinetic temperatures, and minima in their ratios. Because coronal streamers straddle the current sheet close to the sun, the pattern discovered is the 'signal' of a coronal streamer at 1 AU. A superposed epoch analysis of 74 well-defined sector boundary crossings provides verification of the above correlation featuring a pronounced minimum in the helium to hydrogen abundance ratio at the sector boundary passage.

Borrini, G.↗