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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 109 records · Page 6
All sourcesNASA NTRSDOE OSTI
DOE OSTI2024

Non-linear MHD modelling of transients in tokamaks: a review of recent advances with the JOREK code

Transient magneto-hydrodynamic (MHD) events like edge localized modes (ELMs) or disruptions are a concern for magnetic confinement fusion power plants. Research with the MHD code JOREK towards understanding control of such instabilities is reviewed here in a concise way to provide a complete overview, while we refer to the original publications for details. Experimental validation for unmitigated vertical displacement events progressed. The mechanism of vertical force mitigation by impurity injection was identified. Two-way eddy current coupling to CARIDDI was completed. Shattered pellet injection was simulated in JET, KSTAR, ASDEX Upgrade (AUG) and ITER. Benign runaway electron beam termination in JET and ITER was studied. Coupling of kinetic REs to the MHD is ongoing and a virtual RE synchrotron radiation diagnostic was developed. Regarding pedestal physics, regimes devoid of large ELMs in AUG were simulated and predictive JT60-SA simulations are ongoing. For ELM suppression by resonant magnetic perturbations (RMPs), AUG, ITER and EAST simulations were performed. A free boundary RMP model was validated against experiments. Evidence for penetrated magnetic islands at the pedestal top based on AUG experiments and simulations was found. Simulations of the naturally ELM-free quiescent H-mode in AUG and HL-3 show external kink mode formation prevents pedestal build-up towards an ELM within windows of the edge safety factor. With kinetic neutral particles, high field side high density formation in ITER was simulated and with kinetic impurities, tungsten transport in AUG RMP plasmas was studied. To capture turbulent transport, electro-static full-f particle in cell models for ion temperature gradient and trapped electron modes were established and benchmarked. Application to RMP plasmas shows enhanced turbulence in comparison to unperturbed states. Energetic particle interactions with MHD were studied. Flux pumping that prevents the safety factor on axis from dropping below unity was simulated. First non-linear stellarator applications include current relaxation in $l$ = 2 stellarators, while verification for advanced stellarators progresses.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
NASA NTRS1993

LET spectra measurements of charged particles in the P0006 experiment on LDEF

Measurements are under way of the charged particle radiation environment of the Long Duration Exposure Facility (LDEF) satellite using stacks of plastic nuclear track detectors (PNTD's) placed in different locations of the satellite. In the initial work the charge, energy, and linear energy transfer (LET) spectra of charged particles were measured with CR-39 double layer PNTD's located on the west side of the satellite (Experiment P0006). Primary and secondary stopping heavy ions were measured separately from the more energetic particles. Both trapped and galactic cosmic ray (GCR) particles are included, with the latter component being dominated by relativistic iron particles. The results from the P0006 experiment will be compared with similar measurements in other locations on LDEF with different orientation and shielding conditions. The remarkably detailed investigation of the charged particle radiation environment of the LDEF satellite will lead to a better understanding of the radiation environment of the Space Station Freedom. It will enable more accurate prediction of single event upsets (SEU's) in microelectronics and, especially, more accurate assessment of the risk - contributed by different components of the radiation field (GCR's, trapped protons, secondaries and heavy recoils, etc.) - to the health and safety of crew members.

Benton, E. V.↗
DOE OSTI2025

Commissioning of Extended Electron Beam Ion Source at Brookhaven National Laboratory

Here, the Extended Electron Beam Ion Source (EEBIS) has been installed and commissioned at Brookhaven National Laboratory (BNL) hadron accelerator complex in the spring of 2023. EEBIS has replaced its predecessor, RhicEBIS, which provided ions for BNL hadron facilities for over a decade since 2009. The motivations for the source upgrade are to provide higher intensities of the Au 32+ ion beam for the Relativistic Heavy Ion Collider (RHIC) and to provide of an intense source of polarized 3 He 2+ ions for the future Electron Ion Collider (EIC) at BNL. EEBIS is and will continue to be the primary source for a variety of different ion species for the NASA Space Radiation Laboratory (NSRL) at BNL. EEBIS utilizes two identical, two-meter-long unshielded 5T warm bore superconducting solenoids, and it is operated with electron beam current up to 10 A, providing a high-capacity ion traps to fulfill the requirement for high intensity ion beams. The upstream solenoid contains a “short ion trap” with a length of 95 cm, while the “long ion trap” with a length of 178 cm is located inside the downstream solenoid bore. The main features of EEBIS are: * A Gas injection and ionization cell equipped with a Lorenz pulse valve * High-capacity ZAO non-evaporable getter (NEG) custom linear pumping units * In situ apparatus for pumping speed measurements to monitor NEG activation and saturation * “External drift tube” construction with differential pumping stages to provide space for Lorentz pulse valve and 3 He high-field polarization cell * A Ba oxide electron gun cathode. The design of EEBIS as well as the results of its commissioning and first-year operation are presented and discussed.

43 PARTICLE ACCELERATORS↗
DOE OSTI2025

Anode sensitivity calibration of photomultiplier tubes used as a readout of the ELOSS detector

We present and discuss the methodology and results for an anode sensitivity calibration of Photomultiplier Tubes (PMTs) that serve as the optical readout of the Energy Loss Optical Scintillation System (ELOSS). The ELOSS detector, under development at the Facility for Rare Isotope Beams (FRIB), is a gaseous Xe scintillation-based detector designed to identify the atomic number (Z) of nuclear reaction fragments by energy-loss measurement. Variation in the anode sensitivity from tube to tube of commercially available PMTs limits ELOSS from reaching its ultimate Z resolution. A methodical approach to calibrating PMT anode sensitivities to a single target value by systematic PMT gain corrections is presented. Although the calibration process is discussed in terms of its impact on ELOSS performance, the presented method is applicable to any optical detector system composed of a large number of PMTs needing anode sensitivity calibration.

Instrumentation for heavy-ion accelerators↗
NASA NTRS1983

Particle simulations of electrostatic emissions near the lower hybrid frequency

The linear instability and nonlinear saturation of electrostatic emission near the lower hybrid frequency is examined for model cold and warm ion ring distributions and auroral zone parameters. In the cold ring case, a single coherent mode near omega (LH) evolves, and saturates by ion trapping. In the warm ring case, a discrete spectrum of unstable modes separated by the ion gyrofrequency is generated near and above omega (LH). The latter instability saturates by quasilinear diffusion.

Roth, I.↗
DOE OSTI2024

Predictive modeling of NSTX discharges with the updated multi-mode anomalous transport module

Abstract The objective of this study is twofold: firstly, to demonstrate the consistency between the anomalous transport results produced by updated Multi-Mode Model (MMM) version 9.0.4 and those obtained through gyrokinetic simulations; and secondly, to showcase MMM’s ability to predict electron and ion temperature profiles in low aspect ratio, high beta NSTX discharges. MMM encompasses a range of transport mechanisms driven by electron and ion temperature gradients, trapped electrons, kinetic ballooning, peeling, microtearing, and drift resistive inertial ballooning modes. These modes within MMM are being verified through corresponding gyrokinetic results. The modes that potentially contribute to ion thermal transport are stable in MMM, aligning with both experimental data and findings from linear CGYRO simulations. The isotope effects on these modes are also studied and higher mass is found to be stabilizing, consistent with the experimental trend. The electron thermal power across the flux surface is computed within MMM and compared to experimental measurements and nonlinear CGYRO simulation results. Specifically, the electron temperature gradient modes (ETGM) within MMM account for 2.0 MW of thermal power, consistent with experimental findings. It is noteworthy that the ETGM model requires approximately 5.0 ms of computation time on a standard desktop, while nonlinear CGYRO simulations necessitate 8.0 h on 8 K cores. MMM proves to be highly computationally efficient, a crucial attribute for various applications, including real-time control, tokamak scenario optimization, and uncertainty quantification of experimental data.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
NASA NTRS1991

Numerical studies of electron dynamics in oblique quasi-perpendicular collisionless shock waves

Linear and nonlinear electron damping of the whistler precursor wave train to low Mach number quasi-perpendicular oblique shocks is studied using a one-dimensional electromagnetic plasma simulation code with particle electrons and ions. In some parameter regimes, electrons are observed to trap along the magnetic field lines in the potential of the whistler precursor wave train. This trapping can lead to significant electron heating in front of the shock for low beta(e). Use of a 64-processor hypercube concurrent computer has enabled long runs using realistic mass ratios in the full particle in-cell code and thus simulate shock parameter regimes and phenomena not previously studied numerically.

Liewer, P. C.↗
NASA NTRS1994

Proton-induced fragmentation of carbon at energies below 100 MeV

Radiation effects caused by single cosmic ray particles have been studied for many years in radiobiological experiments for different biological objects and biological end-points. Additionally, single event effects in microelectronic devices have gained large interest. There are two fundamental mechanisms by which a single particle can cause radiation effects. On the one hand, a cosmic ray ion with high linear energy transfer can deposit a high dose along its path. On the other hand, in a nuclear collision, a high dose can be deposited by short range particles emitted from the target nucleus. In low earth orbits a large contribution to target fragmentation events originates from trapped protons which are encountered in the South Atlantic Anomaly. These protons have energies up to a few hundred MeV. We study the fragmentation of C, O and Si nuclei - the target nuclei of biological material and microelectronic devices - in nuclear collisions. Our aim is to measure production cross sections, energy spectra, emission directions and charge correlations of the emitted fragments. The present knowledge concerning these data is rather poor. M. Alurralde et al. have calculated cross sections and average energies of fragments produced from Si using the cascade-evaporation model. D.M. Ngo et al. have used the semiempirical cross section formula of Silberberg and Tsao to calculate fragment yields and the statistical model of Goldhaber to describe the reaction kinematics. Cross sections used in these models have uncertainties within a factor of two. Our data will help to test and improve existing models especially for energies below 300 MeV/nucleon. Charge correlations of fragments emitted in the same interaction are of particular importance, since high doses can be deposited if more than one heavy fragment with a short range is produced.

Schmitz, M.↗
DOE OSTI2025

Numerical simulations of three-dimensional ion crystal dynamics in a Penning trap using the fast multipole method

We simulate the dynamics, including laser cooling, of three-dimensional (3-D) ion crystals confined in a Penning trap using a newly developed molecular dynamics-like code. The numerical integration of the ions’ equations of motion is accelerated using the fast multipole method to calculate the Coulomb interaction between ions, which allows us to efficiently study large ion crystals with thousands of ions. In particular, we show that the simulation time scales linearly with ion number, rather than with the square of the ion number. By treating the ions’ absorption of photons as a Poisson process, we simulate individual photon scattering events to study laser cooling of 3-D ellipsoidal ion crystals. Initial simulations suggest that these crystals can be efficiently cooled to ultracold temperatures, aided by the mixing of the easily cooled axial motional modes with the low frequency planar modes. In our simulations of a spherical crystal of 1000 ions, the planar kinetic energy is cooled to several millikelvin in a few milliseconds while the axial kinetic energy and total potential energy are cooled even further. This suggests that 3-D ion crystals could be well suited as platforms for future quantum science experiments.

Zaris, John (ORCID:0009000196476323)↗
DOE OSTI2026

Benchmarking core turbulence and transport predictions for an inductive compact tokamak reactor plasma

Motivated by the need for accurate, timely, and efficient calculations of plasma transport, predictions of plasma turbulence properties made using different TGLF saturation rules are benchmarked against corresponding predictions from linear and nonlinear gyrokinetic CGYRO simulations. This benchmarking is carried out using parameters taken from an inductive burning plasma scenario in a hypothetical compact high-field (R maj = 4 m, B T = 8 T) tokamak, lying in a much different regime of parameter space than either the TGLF calibration regime or current-day experiments. The core turbulent transport in this scenario is predicted to be dominated by ion temperature gradient (ITG) turbulence. In general, the ITG critical gradients predicted by various TGLF saturation rules are quite close to the CGYRO predictions. Both codes predict similar linear ITG growth rates and frequency spectra, as well as their scaling with R/L T i = −Rd ln(T i )/dr. However, TGLF systematically predicts unstable trapped-electron modes (TEMs) above k y ρ s ≃ 0.5 not seen by CGYRO for the same parameters, due to TGLF predicting a lower threshold in R/L T e than CGYRO for TEM onset. It is shown that for this scenario, nonlinear CGYRO simulations predict stiffer ITG turbulence than the TGLF SAT0 and SAT1 saturation rules, with energy fluxes close in magnitude and scaling with R/L T i to what is predicted by the SAT2 saturation rule. Self-consistent core profiles calculated using nonlinear CGYRO flux predictions and the PORTALS transport solver are shown to agree fairly well with corresponding predictions made using the TGLF SAT2 model, including a similar level of density peaking.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
NASA NTRS1995

LDEF contributions to cosmic ray and radiation environments research

LDEF-1 carried three experiments which are producing significant advances in our knowledge of ultra heavy and anomalous cosmic rays, solar flare particles, and heavy nuclei in the trapped belts. Nine other experiments made measurements on the radiation environments or performed dosmetric monitoring. Data from those experiments, and from measurements of induced radioactivity in LDEF components have significantly improved our knowledge of LEO radiation environment. Measurements at various locations shielding depths of radiation absorbed dose, linear energy transfer spectra, proton, neutron and heavy ion fluences, and induced radioactivity have been made, and many of these results have been compared to models. This has allowed the assessment of accuracy, and the potential for improvement, of the models. Serendipitous results from the radiation measurements include the discovery of atmospheric Be-7 plated on the front surface of LDEF, which has motivated a series of new investigations. A sample of measurements and modeling results will be presented, as well as the status of archiving the measurements and models.

Parnell, Thomas A.↗
NASA NTRS1994

Feedback Control of Plasma Instabilities with Charged Particle Beams and Study of Plasma Turbulence

A new non-perturbing technique for feedback control of plasma instabilities has been developed in the Columbia Linear Machine (CLM). The feedback control scheme involves the injection of a feedback modulated ion beam as a remote suppressor. The ion beam was obtained from a compact ion beam source which was developed for this purpose. A Langmuir probe was used as the feedback sensor. The feedback controller consisted of a phase-shifter and amplifiers. This technique was demonstrated by stabilizing various plasma instabilities to the background noise level, like the trapped particle instability, the ExB instability and the ion-temperature-gradient (ITG) driven instability. An important feature of this scheme is that the injected ion beam is non-perturbing to the plasma equilibrium parameters. The robustness of this feedback stabilization scheme was also investigated. The principal result is that the scheme is fairly robust, tolerating about 100% variation about the nominal parameter values. Next, this scheme is extended to the unsolved general problem of controlling multimode plasma instabilities simultaneously with a single sensor-suppressor pair. A single sensor-suppressor pair of feedback probes is desirable to reduce the perturbation caused by the probes. Two plasma instabilities the ExB and the ITG modes, were simultaneously stabilized. A simple 'state' feedback type method was used where more state information was generated from the single sensor Langmuir probe by appropriate signal processing, in this case, by differentiation. This proof-of-principle experiment demonstrated for the first time that by designing a more sophisticated electronic feedback controller, many plasma instabilities may be simultaneously controlled. Simple theoretical models showed generally good agreement with the feedback experimental results. On a parallel research front, a better understanding of the saturated state of a plasma instability was sought partly with the help of feedback. A plasma instability is usually observed in its saturated state and appears as a single feature in the frequency spectrum with a single azimuthal and parallel wavenumbers. The physics of the non-zero spectral width was investigated in detail because the finite spectral width can cause "turbulent" transport. One aspect of the "turbulence" was investigated by obtaining the scaling of the linear growth rate of the instabilities with the fluctuation levels. The linear growth rates were measured with the established gated feedback technique. The research showed that the ExB instability evolves into a quasi-coherent state when the fluctuation level is high. The coherent aspects were studied with a bispectral analysis. Moreover, the single spectral feature was discovered to be actually composed of a few radial harmonics. The radial harmonics play a role in the nonlinear saturation of the instability via three-wave coupling.

Tham, Philip Kin-Wah↗
NASA NTRS1991

Steepening of parallel propagating hydromagnetic waves into magnetic pulsations - A simulation study

The steepening mechanism of parallel propagating low-frequency MHD-like waves observed upstream of the earth's quasi-parallel bow shock has been investigated by means of electromagnetic hybrid simulations. It is shown that an ion beam through the resonant electromagnetic ion/ion instability excites large-amplitude waves, which consequently pitch angle scatter, decelerate, and eventually magnetically trap beam ions in regions where the wave amplitudes are largest. As a result, the beam ions become bunched in both space and gyrophase. As these higher-density, nongyrotropic beam segments are formed, the hydromagnetic waves rapidly steepen, resulting in magnetic pulsations, with properties generally in agreement with observations. This steepening process operates on the scale of the linear growth time of the resonant ion/ion instability. Many of the pulsations generated by this mechanism are left-hand polarized in the spacecraft frame.

Akimoto, K.↗
NASA NTRS1988

Computer simulations of two-pickup-ion instabilities in a cometary environment

This paper presents a one-dimensional electromagnetic hybrid computer simulation of distant cometary environments, in which protons and oxygen ions are injected continuously at the same time. It is demonstrated that, when, instead of a single component, both protons and oxygen ions are injected, the faster growing shorter-wavelength proton-proton right-hand resonant instability dominates the early time physics, leading to linear temporal growth of the fluctuating magnetic field energy density and pitch angle scattering of the protons (but causing no significant response by the nonresonant oxygen ions). At later times, as the injected oxygen ions accumulate sufficient density, the oxygen-proton right-hand resonant instability emerges, exhibiting exponential temporal growth to a relatively large peak amplitude, phase bunching, and magnetically trapping the oxygen ions. At times after peak amplitude, the oxygen-proton fluctuations stochastically accelerate some of the injected protons.

Gary, S. Peter↗
NASA NTRS2015

Radiation Environment Inside Spacecraft

Dr. Patrick O'Neill, NASA Johnson Space Center, will present a detailed description of the radiation environment inside spacecraft. The free space (outside) solar and galactic cosmic ray and trapped Van Allen belt proton spectra are significantly modified as these ions propagate through various thicknesses of spacecraft structure and shielding material. In addition to energy loss, secondary ions are created as the ions interact with the structure materials. Nuclear interaction codes (FLUKA, GEANT4, HZTRAN, MCNPX, CEM03, and PHITS) transport free space spectra through different thicknesses of various materials. These "inside" energy spectra are then converted to Linear Energy Transfer (LET) spectra and dose rate - that's what's needed by electronics systems designers. Model predictions are compared to radiation measurements made by instruments such as the Intra-Vehicular Charged Particle Directional Spectrometer (IV-CPDS) used inside the Space Station, Orion, and Space Shuttle.

O'Neill, Patrick↗
NASA NTRS2000

Analysis of MIR-18 results for physical and biological dosimetry: radiation shielding effectiveness in LEO

We compare models of radiation transport and biological response to physical and biological dosimetry results from astronauts on the Mir space station. Transport models are shown to be in good agreement with physical measurements and indicate that the ratio of equivalent dose from the Galactic Cosmic Rays (GCR) to protons is about 3/2:1 and that this ratio will increase for exposures to internal organs. Two biological response models are used to compare to the Mir biodosimetry for chromosome aberration in lymphocyte cells; a track-structure model and the linear-quadratic model with linear energy transfer (LET) dependent weighting coefficients. These models are fit to in vitro data for aberration formation in human lymphocytes by photons and charged particles. Both models are found to be in reasonable agreement with data for aberrations in lymphocytes of Mir crew members: however there are differences between the use of LET dependent weighting factors and track structure models for assigning radiation quality factors. The major difference in the models is the increased effectiveness predicted by the track model for low charge and energy ions with LET near 10 keV/micrometers. The results of our calculations indicate that aluminum shielding, although providing important mitigation of the effects of trapped radiation, provides no protective effect from the galactic cosmic rays (GCR) in low-earth orbit (LEO) using either equivalent dose or the number of chromosome aberrations as a measure until about 100 g/cm 2 of material is used.

Flight Experiment↗
NASA NTRS1983

Ion-acoustic solitary waves in a magnetized plasma with arbitrary electron equation of state

The oblique propagation of fully nonlinear, slow ion-acoustic solitary waves in a collisionless, low-beta, magnetized plasma is examined. The analysis includes the effects of a finite ion pressure, electron trapping, and multicomponent particle populations. The existence of both compressive and rarefactive modes propagating obliquely to the magnetic field in a plasma with two distinct Boltzmann electron populations and cold ions is demonstrated. It is shown that paired electrostatic shocks observed over the earth's auroral zone may be closely related to the rarefactive modes. As a measure of the collisionless dissipation encountered by the solitary waves, the linear response of the plasma to slow ion-acoustic waves is also examined.

Witt, E.↗
NASA NTRS2002

HPLC/ESI-quadrupole ion trap mass spectrometry for characterization and direct quantification of amphoteric and nonionic surfactants in aqueous samples

An amphoteric (cocamidopropylbetaine, CAPB) and a nonionic (alcohol polyethoxylate, AE) surfactant were characterized by electrospray ionization quadrupole ion trap mass spectrometry (ESI-MS) as to their homologue distribution and ionization/fragmentation chemistry. Quantitative methods involving reversed-phase gradient HPLC and (+)ESI-MSn were developed to directly determine these surfactants in hydroponic plant growth medium that received simulated graywater. The predominant homologues, 12 C alkyl CAPB and 9 EO AE, were monitored to represent the total amount of the respective surfactants. The methods demonstrated dynamic linear ranges of 0.5-250 ng (r2 > 0.996) for CAPB and 8-560 ng (r2 > 0.998) for AE homologue mixture, corresponding to minimum quantification limits of 25 ppb CAPB and 0.4 ppm AE with 20-microL injections. This translated into an even lower limit for individual components due to the polydispersive nature of the surfactants. The procedure was successfully employed for the assessment of CAPB and AE biodegradation in a hydroponic plant growth system used as a graywater bioreactor.

NASA Discipline Life Support Systems↗