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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 91 records · Page 5
All sourcesNASA NTRSDOE OSTI
NASA NTRS1990

Interaction of a neutral cloud moving through a magnetized plasma

Current collection by outgassing probes in motion relative to a magnetized plasma may be significantly affected by plasma processes that cause electron heating and cross field transport. Simulations of a neutral gas cloud moving across a static magnetic field are discussed. The authors treat a low-Beta plasma and use a 2-1/2 D electrostatic code linked with the authors' Plasma and Neutral Interaction Code (PANIC). This study emphasizes the understanding of the interface between the neutral gas cloud and the surrounding plasma where electrons are heated and can diffuse across field lines. When ionization or charge exchange collisions occur a sheath-like structure is formed at the surface of the neutral gas. In that region the crossfield component of the electric field causes the electron to E times B drift with a velocity of the order of the neutral gas velocity times the square root of the ion to electron mass ratio. In addition a diamagnetic drift of the electron occurs due to the number density and temperature inhomogeneity in the front. These drift currents excite the lower-hybrid waves with the wave k-vectors almost perpendicular to the neutral flow and magnetic field again resulting in electron heating. The thermal electron current is significantly enhanced due to this heating.

Goertz, C. K.↗
NASA NTRS2019

The NASA OBPG 2020 On-Orbit Calibration of SNPP VIIRS for Ocean Color Applications

The NASA Ocean Biology Processing Group (OBPG) has continued monitoring the SNPP VIIRS on-orbit calibration for bands M1-M11 over its mission to optimize the calibration for ocean color applications. The OBPG has recently implemented several changes to the calibration scheme: using solar-derived f-factors to detrend the lunar observations; using long-term exponentials of time as basis vectors (along with libration angles) for radiometric fits to any resulting lunar temporal drifts; deriving gain adjustments to the solar f-factors from these exponentials; and deriving gain adjustments due to modulated RSRs outside of the solar/lunar calibration using TOA reference spectra. These calibration changes minimize the impact of uncertainties in any one component of the calibration on the derived f-factors. The final f-factors incorporate VIIRS solar diffuser measurements, h-factor BRDF corrections, lunar-derived gains, and modulated RSR gains. The combined BRDF corrections, lunar gain adjustments, and mRSR gain adjustments define effective h-factors for each band. The improvements in the on-orbit calibration are validated by evaluation of globally-derived anomaly plots of remote sensing reflectance for the ocean color bands. The ultimate goal of the OBPG calibration effort is incorporation of a consistent SNPP VIIRS ocean color data set into the NASA multi-mission ocean color climate data record.

VIIRS↗
DOE OSTI2013

Electromagnetic fluctuations and normal modes of a drifting relativistic plasma

We present an exact calculation of the power spectrum of the electromagnetic fluctuations in a relativistic equilibrium plasma described by Maxwell-Jüttner distribution functions. We consider the cases of wave vectors parallel or normal to the plasma mean velocity. The relative contributions of the subluminal and supraluminal fluctuations are evaluated. Analytical expressions of the spatial fluctuation spectra are derived in each case. These theoretical results are compared to particle-in-cell simulations, showing a good reproduction of the subluminal fluctuation spectra.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2019

PERFORMANCE CHARACTERISTICS OF A VECTOR SENSOR ARRAY IN AN ENERGETIC TIDAL CHANNEL

A compact three-dimensional vector sensor array (termed the NoiseSpotter) was recently developed with the goal of characterizing and localizing sources of sound in energetic environments such as those where marine renewable energy devices are likely to be located. The three vector sensors on the NoiseSpotter are mounted on a bottom platform with each sensor suspended inside an optional flow noise removal shield. The multiple pressure and particle velocity channels on the NoiseSpotter are simultaneously sampled and stored on-board to enable coherent array processing of vector sensor array data. A series of field trials were conducted where the NoiseSpotter was deployed on a bottom platform in an 8 m deep tidal channel in Sequim Bay, Washington. Pure tones were transmitted from a drifting vessel whose distance from the bottom platform varied between 50 m and 500 m. The effect of flow noise on vector sensor array performance is quantified along with the detectability of low intensity sound in an energetic environment. Flow noise removal efficiency for each channel of every vector sensor is demonstrated using multiple metrics derived from the active and reactive intensities computed using the pressure-velocity cross-spectral density matrix. A flow noise removal shield is shown to improve the detectability of low intensity sound such as those that are expected to be emitted by marine renewable energy devices.

Raghukumar, Kaustubha↗
DOE OSTI2026

Anomaly Detection for Online Monitoring of Thermocouple Sensors in the Advanced Test Reactor

This study explores data-driven anomaly detection methods to analyze sensor fail- ures in the Advanced Gas Reactor (AGR) nuclear fuel irradiation experiments. Specifically, we examine failures of thermocouples (TCs), which are critical for mon- itoring and controlling in-reactor temperatures during operation. Failures were pri- marily observed during abrupt power transitions and manifested as sensor drop-outs, drifts, or unexplained behavior. We applied three time-series analysis techniques— rolling mean smoothing, matrix profile, and vector auto-regression (VAR)—to de- tect anomalies in TC data prior to failure events. The rolling mean method effec- tively highlighted deviations aligned with reported failures, while the matrix profile provided partial early warning but sometimes flagged normal fluctuations during power-down periods. VAR shows potential in capturing multivariate dependencies but requires further calibration. A rare case of TC drift was also documented, which did not result in failure, underscoring the challenge of building predictive models with sparse positive examples. Our findings demonstrate that traditional statistical tools can aid anomaly detection but have limited predictive power without richer training data. We propose future directions including synthetic data generation, real- time surrogate modeling, and multi-modal feature integration. This work provides a foundation for applying robust anomaly detection frameworks to mission-critical sensor systems in experimental settings.

11 - NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2013

Quasi-linear heating and acceleration in bi-Maxwellian plasmas

Quasi-linear acceleration and heating rates are derived for drifting bi-Maxwellian distribution functions in a general nonrelativistic case for arbitrary wave vectors, propagation angles, and growth/damping rates. The heating rates in a proton-electron plasma due to ion-cyclotron/kinetic Alfvén and mirror waves for a wide range of wavelengths, directions of propagation, and growth or damping rates are explicitly computed.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
NASA NTRS1987

Magnetic braking in weakly ionized media

The combined magnetic braking-ambipolar diffusion problem in weakly ionized, rigidly rotating disks is studied. An analytical solution is presented for a disk whose angular velocity and magnetic yield vectors are aligned with the symmetry axis, illustrating the effects of the relative azimuthal drift of neutrals and ions. The effects of radial drift are added, commenting on the ratio of the characteristic ambipolar diffusion and magnetic braking time scales in high-mass and low-mass disks. A numerical calculation is used to show the combined action of these two processes.

Konigl, Arieh↗
DOE OSTI2016

A Study of a Mini-Drift GEM Tracking Detector

In this paper, a GEM tracking detector with an extended drift region has been studied as part of an effort to develop new tracking detectors for future experiments at RHIC and for the Electron Ion Collider that is being planned for BNL or JLAB. The detector consists of a triple GEM stack with a 1.6 cm drift region that was operated in a mini TPC type configuration. Both the position and arrival time of the charge deposited in the drift region were measured on the readout plane which allowed the reconstruction of a short vector for the track traversing the chamber. The resulting position and angle information from the vector could then be used to improve the position resolution of the detector for larger angle tracks, which deteriorates rapidly with increasing angle for conventional GEM tracking detectors using only charge centroid information. Two types of readout planes were studied. One was a COMPASS style readout plane with 400 μm pitch XY strips and the other consisted of 2 × 10 mm 2 chevron pads. The detector was studied in test beams at Fermilab and CERN, along with additional measurements in the lab, in order to determine its position and angular resolution for incident track angles up to 45 degrees. Several algorithms were studied for reconstructing the vector using the position and timing information in order to optimize the position and angular resolution of the detector for the different readout planes. Finally, applications for large angle tracking detectors at RHIC and EIC are also discussed.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
NASA NTRS1982

Large sounding rockets as a base for probing the distant magnetosphere

The Echo program's use of large sounding rockets to inject electron beams into the outer trapping region where the earth's plasma sheet interacts with the inner magnetosphere is discussed. The beams pass through the plasma sheet and the trapping region, reflect at the southern hemisphere conjugate point and return to the vicinity of the rocket where they are detected and analyzed for acceleration and diffusion processes which may also be responsible for the radiation belts. The motion of electron beams in the magnetosphere is discussed from the standpoint of single particle motion, and the trajectories of electrons injected with known energy, known angle between the electron velocity vector and the local magnetic field vector, and known position are examined. The interaction between the rocket motion and the electron drift motion is described, and the advantages and drawbacks of beam detection by optical methods and by throwaway detectors are compared. Planned Echo experiments using the Space Shuttle are discussed

Winckler, J. R.↗
DOE OSTI2020

Sensor Drift Estimation for Reactor Systems by Fusing Multiple Sensor Measurements

A nuclear power plant is instrumented with a variety of sensors that monitor its variables to estimate the state and initiate safety actions, if needed. We address the problem of estimating drifts or errors in sensor measurements due to factors such as calibration changes. We propose an information fusion method that uses measurements from other sensors to generate an estimate of a sensor measurement, and its difference from an actual measurement provides an error estimate. We present two fusers based on the ensemble of trees and support vector machine that are trained using sensor measurements collected at an emulated test loop of a pressurized water reactor under no-drift conditions. We present error estimates for a differential pressure sensor of the heat exchanger of the primary coolant system, under twenty controlled scenarios using the test loop. Both positive and negative errors are captured by both methods in scenarios involving calibration drifts, blocking, air gap and electromagnetic interference. The root mean square errors of estimated drifts are typically within 2% percent of the maximum.

Rao, Nageswara↗
DOE OSTI2015

Development of a vector-tensor system to measure the absolute magnetic flux density and its gradient in magnetically shielded rooms

Several experiments in fundamental physics demand an environment of very low, homogeneous, and stable magnetic fields. For the magnetic characterization of such environments, we present a portable SQUID system that measures the absolute magnetic flux density vector and the gradient tensor. This vector-tensor system contains 13 integrated low-critical temperature (LTc) superconducting quantum interference devices (SQUIDs) inside a small cylindrical liquid helium Dewar with a height of 31 cm and 37 cm in diameter. The achievable resolution depends on the flux density of the field under investigation and its temporal drift. Inside a seven-layer mu-metal shield, an accuracy better than ±23 pT for the components of the static magnetic field vector and ±2 pT/cm for each of the nine components of the gradient tensor is reached by using the shifting method.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2014

RF cavity design and qualification for proton accelerator

Alvarez type Drift Tube Linac (DTL) is used for acceleration of proton beam in low energy section of beta ranging from 0.04 to 0.40. DTL is cylindrical RF cavity resonating in TM010 mode at 352.21 MHz frequency. It consists of array of drift tubes arranged ensuring that DTL centre and Drift Tube centre are concentric. The Drift Tubes also houses Permanent Magnet Quadrupole for transverse focusing of proton beam. A twelve cell prototype of DTL section is designed, developed and fabricated at Bhabha Atomic Research Centre, Trombay. Complete DTL accelerator consists of eight such DTL sections. High frequency microwave simulations are carried out in SOPRANO, vector fields and COMSOL simulation software. This prototype DTL is 1640.56 mm long cavity with 520 mm ID, 600 mm OD and consists of eleven Drift Tubes, two RF end flanges, three slug tuners, six post couplers, three RF field monitors, one RF waveguide coupler, two DN100 vacuum flanges and DTL tank platform with alignment features. Girder based Drift tube mounting arrangement utilizing uncompressing energy of disc springs for optimum combo RF-vacuum seal compression is worked out and implemented. This paper discusses design of this RF vacuum cavity operating at high accelerating field gradient in ultra-high vacuum. Detailed vacuum design and results of RF and vacuum qualifications are discussed. Results on mechanical accuracy achieved on scaled pre-prototype are also presented. Paper summarizes the engineering developments carried out for this RF cavity and brings out the future activities proposed in indigenous development of high gradient RF cavities for ion accelerators. (author)

43 PARTICLE ACCELERATORS↗
DOE OSTI2024

Flowing plasma rearrangement in the presence of static perturbing fields

Charged particles interacting with electromagnetic waves have a portion of their energy tied up in wave-driven oscillations. When these waves are localized to the exhaust of linear magnetic confinement systems, this ponderomotive effect can be utilized to enhance particle confinement. The same effect can be derived for particles moving via an E×B drift into a region of a static perturbation to the electromagnetic fields which has a large wave vector component in the direction of the motion. In this work, we use a simplified slab model to self-consistently solve for the electromagnetic fields within the fluid flowing plasma of a static flute-like (k∥=0) perturbation and evaluate the resulting ponderomotive potential. We find that two types of perturbations can exist within the flowing plasma, which are an O wave and an X wave in the frame moving with the fluid. In the case of tenuous plasma, these perturbations are magnetostatic or electrostatic multipole-analog perpendicular to the guiding magnetic field in the lab frame, respectfully. For denser plasmas, the O wave-like perturbation is screened at the electron skin depth scale, and the X wave-like perturbation is a combination of a similar perpendicular electric perturbation and parallel magnetic perturbation. The ponderomotive potential generated in the X wave-like case is gyrofrequency-dependent and can be used as either potential barriers or potential wells, depending on the direction of the flow velocity.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2014

Minor ion heating in spectra of linearly and circularly polarized Alfvén waves: Thermal and non-thermal motions associated with perpendicular heating

Minor ion (such as He{sup 2+}) heating via nonresonant interaction with spectra of linearly and circularly polarized Alfvén waves (LPAWs and CPAWs hereafter) is studied. The obtained analytic solutions are in good agreement with the simulation results, indicating that newborn ions are heated by low-frequency Alfvén waves with finite amplitude in low-beta plasmas such as the solar corona. The analytic solutions also reproduce the preferential heating of heavy ions in the solar wind. In the presence of parallel propagating Alfvén waves, turbulence-induced particle motion is clearly observed in the wave (magnetic field) polarized directions. After the waves diminish, the newborn ions are heated, which is caused by the phase difference (randomization) between ions due to their different parallel thermal motions. The heating is dominant in the direction perpendicular to the ambient magnetic field. The perpendicular heating, η=(T{sub i⊥}{sup R}−T{sub i0⊥}{sup R})/T{sub i0⊥}{sup R} (where T{sub i0⊥}{sup R} and T{sub i⊥}{sup R} are the perpendicular temperature of species i before and after genuine heating, respectively), in the spectrum of CPAWs is a factor of two stronger than that of LPAWs. Moreover, we also study the effect of field-aligned differential flow speed of species i relative to H{sup +}, δv{sub ip}=(v{sub i}−v{sub p})·B/|B| (where v{sub i} and v{sub p} denote vector velocities of the H{sup +} and species i, respectively), on the perpendicular heating. It reveals that large drift speed, v{sub d}=δv{sub ip}, has an effect on reducing the efficiency of perpendicular heating, which is consistent with observations.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2018

Laning and clustering transitions in driven binary active matter systems

It is well known that a binary system of nonactive disks that experience driving in opposite directions exhibits jammed, phase separated, disordered, and laning states. In active matter systems, such as a crowd of pedestrians, driving in opposite directions is common and relevant, especially in conditions which are characterized by high pedestrian density and emergency. In such cases, the transition from laning to disordered states may be associated with the onset of a panic state. In this study, we simulate a laning system containing active disks that obey run-and-tumble dynamics, and we measure the drift mobility and structure as a function of run length, disk density, and drift force. The activity of each disk can be quantified based on the correlation timescale of the velocity vector. We find that in some cases, increasing the activity can increase the system mobility by breaking up jammed configurations; however, an activity level that is too high can reduce the mobility by increasing the probability of disk-disk collisions. In the laning state, the increase of activity induces a sharp transition to a disordered strongly fluctuating state with reduced mobility. We identify a novel drive-induced clustered laning state that remains stable even at densities below the activity-induced clustering transition of the undriven system. Lastly, we map out the dynamic phase diagrams highlighting transitions between the different phases as a function of activity, drive, and density.

36 MATERIALS SCIENCE↗
NASA NTRS1984

Annihilation of angular momentum drift during spinning-up and thrusting maneuvers of rigid bodies

A very simple, yet accurate, heuristic solution for the spiral path of the angular momentum vector during spin-up and spin-down maneuvers of rigid body spacecraft is presented. A two-burn scheme is proposed consisting of a burn, a coast, and a second burn of the spin thruster. The appropriate burn times are found by a transcendental equation similar to Kepler's equation. Numerical results verify the accuracy of the burn, coast, and burn times given by closed form expressions. The scheme can also be applied to the problem of axial thrusting during constant spin.

Longuski, J. M.↗
NASA NTRS1978

Measurements of the Poynting vector of standing hydromagnetic waves at geosynchronous orbit

The observation is discussed of a train of hydromagnetic waves with a period of about 150 sec seen at synchronous orbit by the ATS 6 spacecraft on June 27, 1974. The critical observation is a phase shift of 90 deg between east-west oscillations of the particle flow and the east-west component of magnetic field oscillations. This phase shift alone suggests a standing rather than a propagating hydromagnetic wave. Careful processing of the particle data makes it possible to determine the drift velocity and hence the electric field of the wave. The wave electric field together with the time-varying magnetic field reveals an oscillating Poynting vector with zero mean component aligned with the ambient magnetic field and nonzero azimuthal (westward) component.

Cummings, W. D.↗