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Davis, W. M.

Publications and source records attributed to Davis, W. M..

17 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2016

Control and data acquisition upgrades for NSTX-U

The extensive NSTX Upgrade (NSTX-U) Project includes major components which allow a doubling of the toroidal field strength to 1 T, of the Neutral Beam heating power to 12 MW, and the plasma current to 2 MA, and substantial structural enhancements to withstand the increased electromagnetic loads. The maximum pulse length will go from 1.5 to 5 s. The larger and more complex forces on the coils will be protected by a Digital Coil Protection System, which requires demanding real-time data input rates, calculations and responses. The amount of conventional digitized data for a given pulse is expected to increase from 2.5 to 5 GB per second of pulse. 2-D Fast Camera data is expected to go from 2.5 GB/pulse to 10, and another 2 GB/pulse is expected from new IR cameras. Our network capacity will be increased by a factor of 10, with 10 Gb/s fibers used for the major trunks. 32-core Linux systems will be used for several functions, including between-shot data processing, MDSplus data serving, between-shot EFIT analysis, real-time processing, and for a new capability, between-shot TRANSP. As a result, improvements to the MDSplus events subsystem will be made through the use of both UDP and TCP/IP based methods and the addition of a dedicated “event server”.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2016

Blob structure and motion in the edge and SOL of NSTX

Here, the structure and motion of discrete plasma blobs (a.k.a. filaments) in the edge and scrape-off layer of NSTX is studied for representative Ohmic and H-mode discharges. Individual blobs were tracked in the 2D radial versus poloidal plane using data from the gas puff imaging diagnostic taken at 400 000 frames s -1 . A database of blob amplitude, size, ellipticity, tilt, and velocity was obtained for ~45 000 individual blobs. Empirical relationships between various properties are described, e.g. blob speed versus amplitude and blob tilt versus ellipticity. The blob velocities are also compared with analytic models.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2014

Effect of Deuterium Gas Puff On The Edge Plasma In NSTX

This paper describes a detailed examination of the effects of a relatively small pulsed deuterium gas puff on the edge plasma and edge turbulence in NSTX. This gas puff caused little or no change in the line-averaged plasma density or total stored energy, or in the edge density and electron temperature up to the time of the peak of the gas puff. The radial profile of the Dα light emission and the edge turbulence within this gas puff did not vary significantly over its rise and fall, implying that these gas puffs did not significantly perturb the local edge plasma or edge turbulence. These measurements are compared with modeling by DEGAS 2, UEDGE, and with simplified estimates for the expected effects of this gas puff.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2013

Comparison of edge turbulence imaging at two different poloidal locations in the scrape-off layer of Alcator C-Mod

This paper describes 2D imaging measurements of plasma turbulence made in the scrape-off layer of the Alcator C-Mod tokamak simultaneously at two different poloidal locations, one near the outer midplane and the other near the divertor X-point region. These images were made with radial and poloidal resolution using two gas puff imaging diagnostics not directly connected along a B field line. The turbulence correlation structure has a significantly different tilt angle with respect to the local flux surfaces for the midplane and X-regions, and a slightly different ellipticity and size. The time-averaged turbulence velocities can be different in the midplane and X-regions, even within the same flux surface in the same shot. The structures are partially consistent with a magnetic flux tube mapping model, and the velocities are compared with various models for turbulence flow.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2013

Comparison of Edge Turbulence Imaging at Two Different Poloidal Locations in the Scrape-off Layer of Alcator C-Mod

This paper describes 2-D imaging measurements of plasma turbulence made in the scrape-off layer of the Alcator C-Mod tokamak simultaneously at two different poloidal locations, one near the outer midplane and the other near the divertor X-point region. These images were made with radial and poloidal resolution using two gas puff imaging (GPI) diagnostics, which were not directly connected along a B field line. The turbulence correlation structure has a significantly different tilt angle with respect to the local flux surfaces for the midplane and X-regions, and a slightly different ellipticity and size. The time-averaged turbulence velocities can be different in the midplane and Xregions, even within the same flux surface in the same shot, and in most cases the fluctuations in poloidal velocity in these two regions were not correlated. These structures are partially consistent with a magnetic flux tube mapping model, and the velocities are compared with various poloidal flow models.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2012

Plot/SurfW: Plotting Utility for EDGE2D Output

This report describes a utility that was developed to display EDGE2D results. The utility is focused on results that relate to impurity density, velocity, and particle fluxes in the SOL and divertor. Due to the complicated nature of 2D impurity sources, the concentration of the thermal force near the separatrix and near the divertor entrance, the impurity flow pattern and impurity densities are not necessarily easy to visualize. Thus, we wanted a utility that allowed simple and quick visualization of the impurity behavior. In order to achieve this we overlaid the divertor hardware for plots inside the divertor and we expanded the appearance of the main chamber SOL by plotting distance along the field lines vs. SOL depth with the density (or velocity or flux or other quantity) the false colour. Also, we allowed for the plotted variable to be a function of the other EDGE2D result variables.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
NASA NTRS1993

Adjustable Powder Injector For Vacuum Plasma Sprayer

Attachment for plasma spray gun provides four degrees of freedom for adjustment of position and orientation at which powder injected externally into plasma flame. Manipulator provides for adjustment of pitch angle of injection tube: set to inject powder at any angle ranging from perpendicular to parallel to cylindrical axis. Scribed lines on extension bar and manipulator indicate pitch angle of extension tube. Collar changed to adapt injector to different gun.

Burns, D. H.↗
NASA NTRS1992

Reduction of Marine Magnetic Data for Modeling the Main Field of the Earth

The marine data set archived at the National Geophysical Data Center (NGDC) consists of shipborne surveys conducted by various institutes worldwide. This data set spans four decades (1953, 1958, 1960-1987), and contains almost 13 million total intensity observations. These are often less than 1 km apart. These typically measure seafloor spreading anomalies with amplitudes of several hundred nanotesla (nT) which, since they originate in the crust, interfere with main field modeling. The source for these short wavelength features are confined within the magnetic crust (i.e., sources above the Curie isotherm). The main field, on the other hand, is of much longer wavelengths and originates within the earth's core. It is desirable to extract the long wavelength information from the marine data set for use in modeling the main field. This can be accomplished by averaging the data along the track. In addition, those data which are measured during periods of magnetic disturbance can be identified and eliminated. Thus, it should be possible to create a data set which has worldwide data distribution, spans several decades, is not contaminated with short wavelengths of the crustal field or with magnetic storm noise, and which is limited enough in size to be manageable for the main field modeling. The along track filtering described above has proved to be an effective means of condensing large numbers of shipborne magnetic data into a manageable and meaningful data set for main field modeling. Its simplicity and ability to adequately handle varying spatial and sampling constraints has outweighed consideration of more sophisticated approaches. This filtering technique also provides the benefits of smoothing out short wavelength crustal anomalies, discarding data recorded during magnetically noisy periods, and assigning reasonable error estimates to be used in the least square modeling. A useful data set now exists which spans 1953-1987.

Baldwin, R. T.↗
NASA NTRS1984

LANDSAT-4 horizon scanner performance evaluation

Representative data spans covering a little more than a year since the LANDSAT-4 launch were analyzed to evaluate the flight performance of the satellite's horizon scanner. High frequency noise was filtered out by 128-point averaging. The effects of Earth oblateness and spacecraft altitude variations are modeled, and residual systematic errors are analyzed. A model for the predicted radiance effects is compared with the flight data and deficiencies in the radiance effects modeling are noted. Correction coefficients are provided for a finite Fourier series representation of the systematic errors in the data. Analysis of the seasonal dependence of the coefficients indicates the effects of some early mission problems with the reference attitudes which were computed by the onboard computer using star trackers and gyro data. The effects of sun and moon interference, unexplained anomalies in the data, and sensor noise characteristics and their power spectrum are described. The variability of full orbit data averages is shown. Plots of the sensor data for all the available data spans are included.

Bilanow, S.↗
NASA NTRS1982

Improved definition of crustal magnetic anomalies for MAGSAT data

The routine correction of MAGSAT vector magnetometer data for external field effects such as the ring current and the daily variation by filtering long wavelength harmonics from the data is described. Separation of fields due to low altitude sources from those caused by high altitude sources is affected by means of dual harmonic expansions in the solution of Dirichlet's problem. This regression/harmonic filter procedure is applied on an orbit by orbit basis, and initial tests on MAGSAT data from orbit 1176 show reduction in external field residuals by 24.33 nT RMS in the horizontal component, and 10.95 nT RMS in the radial component.

Brown, R. D.↗
NASA NTRS1979

A Geophysical Atlas for Interpretation of Satellite-derived Data

A compilation of maps of global geophysical and geological data plotted on a common scale and projection is presented. The maps include satellite gravity, magnetic, seismic, volcanic, tectonic activity, and mantle velocity anomaly data. The Bibliographic references for all maps are included.

Lowman, P. D., Jr.↗
NASA NTRS1975

A global magnetic anomaly map

A subset of Pogo satellite magnetometer data has been formed that is suitable for analysis of crustal magnetic anomalies. Through the use of a thirteenth-order field model fit to these data, magnetic residuals have been calculated over the world to latitude limits of plus or minus 50 deg. These residuals, averaged over 1-degree latitude-longitude blocks, represent a detailed global magnetic anomaly map derived solely from satellite data. The occurrence of these anomalies on all individual satellite passes independent of local time and their decay as altitude increases imply a definite internal origin. Their wavelength structure and their correlation with known tectonic features further suggest that these anomalies are primarily of geologic origin and have their sources in the lithosphere.

Regan, R. D.↗
NASA NTRS1974

A global magnetic anomaly map

A subset of POGO satellite magnetometer data has been formed that is suitable for analysis of crustal magnetic anomalies. Using a thirteenth order field model, fit to these data, magnetic residuals have been calculated over the world to latitude limits of plus 50 deg. These residuals averaged over one degree latitude-longitude blocks represent a detailed global magnetic anomaly map derived solely from satellite data. Preliminary analysis of the map indicates that the anomalies are real and of geological origin.

Regan, R. D.↗
NASA NTRS1973

The detection of intermediate size magnetic anomalies in Cosmos-49 and OGO-2, 4, and 6 data

Benkova, Dolginov, and Simonenko have recently reported the presence of intermediate size magnetic anomalies in the data from COSMOS-49 and hypothesized a crustal and/or upper mantle origin. The spherical harmonic models of the internal potential function were examined, based on the OGO-2, 4, and 6 data (POGO (10/68) and later models), and verified the locations and amplitudes of those anomalies whose wavelengths approximate 4000 km. The comparison was made by subtracting a field model developed with a truncated series of n* = 9 from one computed with n* = 11 and generating a residual map equivalent to the COSMOS-49 data. The patterns of delta F so computed from POGO were then compared with the IZMIRAN maps and also were analyzed statistically, in both the spatial and frequency domains, using residuals computed from the raw COSMOS-49 data with the n* = 9 COSMOS-49 field model as reference. The two sets of data were thus derived from completely independent sets of observations and field references. The two patterns are shown to agree very well over the whole earth surface up to the 50 deg latitude limit of COSMOS-49.

Regan, R. D.↗
NASA NTRS1973

The detection of 'intermediate' size magnetic anomalies in Cosmos 49 and OGO 2, 4, 6 data.

Benkova, Dolginov and Simonenko have recently reported the presence of intermediate size magnetic anomalies from Cosmos 49 data and hypothesized a crustal and/or upper mantle origin for these. We have examined the spherical harmonic models of the internal potential function, based on the OGO 2, 4 and 6 data and verified the locations and amplitudes of those anomalies with wavelengths of approximately 4000 km. The patterns of delta-F so computed were then compared with the IZMIRAN maps and also were analyzed statistically, in both the spatial and frequency domains, using residuals computed from the raw Cosmos 49 data. The two sets of data were thus derived from completely independent sets of observations and field references. The two patterns are shown to agree very well over the whole earth surface up to the 50 deg latitude limit of Cosmos 49.

Regan, R. D.↗