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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 NTRS1985

Synopsis of the D- and E-regions during the energy budget campaign

Electron density profiles derived from rocket-borne measurements are presented. These data were obtained at two different sites in northern Scandinavia under various degrees of geophysical disturbance. The observed electron density profiles are related to ionospheric absorption as observed with the dense riometer network in that area.

Friedrich, M.↗
NASA NTRS1979

Ionospheric modeling at Air Force Global Weather Central

The four Dimensional Ionospheric Model (4-D) is described. The 4-D integrates a wide variety of ionospheric data types into a consistent ionospheric specification. At each observing location, the 4-D reduces an entire electron density profile to four weighting coefficients. These weighting coefficients are interconnected in time and space by spectral analysis techniques. The resultant field of spectral coefficients can be used to reconstruct an electron density profile at any latitude, longitude and time.

Tascione, T. F.↗
NASA NTRS1976

Model ionospheres of Jupiter

The principal concepts presently involved in modeling the Jovian ionosphere are reviewed. A model ionosphere is developed on the basis of our present knowledge of atmospheric composition, relevant chemical and ion-molecule reactions, with their associated rate constants. The shortcomings of this model are discussed when it is compared with the electron density profile obtained from the Pioneer 10 radio occultation data. It is demonstrated that the apparent great extent of the observed topside ionosphere may imply a hot thermosphere, as if Jupiter sustained a corona. Some of the layers observed in the electron density profile may be due to sporadic-E like clustering of protons and other ions.

Atreya, S. K.↗
NASA NTRS1992

Electron number density profiles for the Aeroassist Flight Experiment

The basic features of a Microwave Reflectometer Ionization Sensor (MRIS) as designed for utilization on the Aeroassist Flight Experiment are described. A parametric study of the effects of trajectory and unknowns in the thermochemical nonequilibrium models for translational and vibrational-electronic energy exchange rates, reaction rates, and the average electronic excitation level of atoms is performed to illustrate how the MRIS data may be employed for code validation. This study, implemented with program LAURA, shows a particular sensitivity of the onset and severity of an electron avalanche phenomena associated with changes in these physical models.

Greendyke, Robert B.↗
NASA NTRS1973

Studies of the structure of the plasmasphere as seen by radiosounder measurements aboard the Alovetti-satellite

The structure of the plasmasphere was studied as seen by radiosounder measurements aboard the Alovetti-2 satellite. Magnetic tape data files were obtained from the NASA Ames Research Center to give a reasonably complete set of high latitude electron density profiles. Considerable effort was expended to develop models of ion flow in the topside ionosphere. These models took both H(+) and O(+) into account and permitted various parameter studies to be made of the various factors which affect H(+) escape in polar wind flows. The results of these studies are included. Extensive computer programs were written to display the measured electron density profiles in ways useful to geophysical analysis. The expected mid-latitude trough was easily discernable in the nightime ionosphere at locations expected from similar observations of the plasmapause. In the dayside ionosphere, however, it proved extremely difficult to find any trough-like phenomena. Using the previously developed computer models, it was possible to study the region where the plasmapause appeared to be absent. It was found that over much of the dayside, large fluxes were computed well inside the plasmapause extending down to L-shells as low as 2.5.

Banks, P. M.↗
NASA NTRS1972

Electron density measurements of an inhomogeneous plasma using millimeter wave Fabry-Perot interferometers.

The electron density of a laboratory generated inhomogeneous plasma was measured using 60-90, GHz flat-plate and 150 GHz semi-confocal Fabry-Perot interferometers. The plasma was a negative glow-type and had a measured parabolic electron density profile. An analytical comparison between the derived equations of electron density for an assumed homogeneous plasma slab and an inhomogeneous plasma with parabolic distribution showed that the slab approximation was valid for such a profile. Comparison of measured values of electron density with those using X-band and K-band interferometers for the same plasma indicated good agreement.

Kendall, B. M.↗
NASA NTRS1978

Interpretation of the shape factor at Ootacamund, India

The paper deals with equatorial ATS-6 measurements of the shape factor, F, interpreted in terms of the shape of the electron density profile along the ray path. The observed rapid increase in F at sunrise is attributed to EUV production of ionization in the E and F regions. The evening decrease is seen to result from an upward drift of the F region at sunset and the evening decay of the E and bottomside F regions. The nighttime peak, or plateau, is caused by gradual decrease of the electron density profile.

Donnelly, R. F.↗
NASA NTRS1974

Comparisons of techniques for measurement of D-region electron densities

This paper reviews the ground-based and rocket techniques that are presently being used to determine electron density profiles in the ionospheric D region. Ground-based techniques include VLF, LF, and MF sounding; differential absorption and differential phase measurements using partial reflections; wave interaction; and incoherent scatter. Rocket techniques include differential absorption and Faraday rotation in association with high-resolution dc probes calibrated by means of the radio measurements. The characteristics of the aforementioned techniques are presented, including time and height resolution, accuracy estimates, preferred height ranges, and problems encountered. Electron density profiles obtained with these techniques are presented for comparable solar zenith angles and undisturbed solar and geophysical conditions.

Sechrist, C. F., Jr.↗
NASA NTRS1976

Stark broadening of Balmer lines in the density range /2-8/ x 10 to the 14/cu cm

Experimental profiles of the hydrogen Balmer lines (H gamma-H sub 10) have been measured over the density range (2-8) x 10 to the 14/cu cm and compared with theoretical profiles. Electron densities were measured using a multipass interferometer, while plasma homogeneity was demonstrated using a Langmuir probe. Electron temperatures were in the range 1-2.0 eV. The electron density as deduced from line profiles tended to be as much as 10% lower than that from the interferometer at higher densities. At lower densities, the two methods agreed to within experimental error. Evidence for asymmetries on the line wings was noted.

Bengtson, R. D.↗
DOE OSTI2024

Prediction of transport in the JET DTE2 discharges with TGLF and NEO models using the TGYRO transport code

Abstract The JET Deuterium-Tritium-Experiment Campaign 2 (DTE2) has demonstrated the highest-ever fusion energy production. To forecast the transport dynamics within these discharges, the TGLF and NEO models within the TGYRO transport code were employed. A critical development in this study is the new quasilinear transport model, TGLF-SAT2, specifically designed to resolve discrepancies identified in JET deuterium discharges. This model accurately describes the saturated three-dimensional (3D) fluctuation spectrum, aligning closely with a database of nonlinear CGYRO turbulence simulations, thereby enhancing the predictive accuracy of TGYRO simulations. In validating against the JET DTE2 discharges across two primary operating scenarios, TGYRO effectively predicted the temperature profiles within a broad radial window ( ρ ∼ 0.2–0.85), though with minor ion temperature discrepancies near the core. However, a consistent underprediction of electron density profiles by 20% across the simulation domain was noted, indicating areas for future refinement. To achieve a self-consistent steady-state solution based on the JET DTE2 discharges, an integrated modeling workflow TGYRO-STEP within the OMFIT framework was introduced. This workflow iterates among the core transport, the pedestal pressure and the MHD equilibrium, ultimately yielding a converged solution that significantly reduces dependence on experimental boundary conditions for temperature and density profiles. The integrated simulation results show negligible differences in electron density and temperature profiles compared to standalone TGYRO modeling, while the ion temperature profile is lower due to the updated boundary condition in TGYRO-STEP. The application of the TGYRO-STEP workflow to JET DTE2 discharges serves as a crucial test to validate its robustness and highlights its limitations, providing valuable insights for its potential future application in ITER and Fusion Power Plant deuterium and tritium prediction modeling.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2024

Electron Density Measurements Using USPR (Final Scientific/Technical Report)

UC Davis has fabricated an ultrashort pulse reflectometer (USPR) diagnostic instrument for electron density profile measurements on compact, short duration, magnetically-confined fusion-energy concept devices such as spheromaks and FRCs. The USPR system transmits extremely short duration (~few nsec) chirped waveforms that together span 29 to 75 GHz. These chirped waveforms illuminate and reflect from the target plasma, with each frequency component reflecting from a different density layer (higher frequencies probe deeper into the plasma before reflecting). The reflected waveforms are split into roughly 42 different frequencies; time-of-flight (TOF) measurements made at each frequency with high resolution (~25 psec measurement resolution which corresponds to ~5 mm). These TOF data may then be inverted via software to generate electron density profiles with high time resolution (~10 μsec). At the heart of the system is a field programmable gate array (FPGA) based controller which collects and processes all of the USPR data in addition to generating all of the control signals required for maximum flexibility. The FPGA controller has the software flexibility to be easily reconfigured for different plasma devices, and the entire system sufficiently compact to be easily and quickly transported between devices. A high speed impulse generator was transformed into a set of three ultrashort pulse transmitter chirps using a combination of dispersive waveguide, frequency doublers and high-pass filters. A mm-wave controller was fabricated to sequentially switch between the three chirps, directing the chirps one-by-one to three different mm-wave assemblies spanning 29-75 GHz. Each mm-wave assembly consists of a high power active multiplier chain which converts the transmitter chirp to higher frequencies, and a broadband mixer which downconverts the reflected waveform to the 2-18 GHz range of the UPSR receiver. The 16-channel receiver (shared by all 3 mm-wave assemblies) was fabricated employing custom TOF modules capable of operating at a high 1 MHz sampling rate. Laboratory testing of the full system revealed the presence of unwanted harmonics from the multiplication process, with interference observed in the downconverted reflections at selected frequency channels that could not be completely filtered out. Additional interference effects arising from internal reflections within the mm-wave assemblies were minimized using a high-speed switch which served to “gate out” much of these reflections. The USPR diagnostic was transported and installed onto the HIT-SIU plasma device, becoming operational on 11/08/2022. Although designed to span 3 distinct mm-wave bands, the HIT-SIU plasmas at this time were sufficiently low density such that only the lowest of the three bands was likely to have strong plasma reflections. The system was then set to operate on only the lowest band (assembly #1), with data collected every 1 μsec rather than 3 μsec which would have been the case when cycling through all three bands. Connected to HIT-SIU, time-varying plasma reflections were observed on 9 of 16 possible frequency channels. Close examination of the data collected revealed issues previously unobserved in laboratory testing, associated with (a) reflections from the small aperture horns required for operation within the HIT-SIU device, and (b) a dependence of the recorded TOF with the threshold voltage of a given channel. Plans were made to address each of these issues before undertaking any future campaigns.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗