Search NASA⌕ Search

SEARCH · Search NASA

Results for “ELECTRONIC LEVEL”

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 217 records · Page 12
All sourcesNASA NTRSDOE OSTI
NASA NTRS1983

The ISPM solar-wind plasma experiment

The ISPM solar wind plasma experiment accurately characterizes the bulk flow and internal state conditions of the interplanetary plasma in three dimensions at all heliographic distances and heliographic latitudes reached by the spacecraft. Solar wind electrons, protons, alpha particles, and heavier ions are measured. Oxygen, silicon, and iron ions at various charge levels are resolved. Electrons and ions are measured simultaneously with independent curved-plate electrostatic analysers equipped with multiple continuous channel electron multipliers arranged so that particle velocity distributions are suitably resolved without gaps in spacecraft polar-angle space. Electrons with energies between 1 and 900 eV are detected at 7 polar angles and various combinations of azimuth angle to cover the unit sphere comprehensively. Ions are detected between 257 eV/Q and 35 keV/Q. Data matrices are obtained every 4 min when the spacecraft is actively transmitting and every 8 min during storage periods. These matrices contain sufficient energy and angle resolution to permit detailed calculations of ion velocity distributions.

Bame, S. J.↗
NASA NTRS2016

Probing Acceleration and Turbulence at Relativistic Shocks in Blazar Jets

Diffusive shock acceleration (DSA) at relativistic shocks is widely thought to be an important acceleration mechanism in various astrophysical jet sources, including radio-loud active galactic nuclei such as blazars. Such acceleration can produce the non-thermal particles that emit the broad-band continuum radiation that is detected from extragalactic jets. An important recent development for blazar science is the ability of Fermi-Large Area Telescope spectroscopy to pin down the shape of the distribution of the underlying non-thermal particle population. This paper highlights how multiwavelength spectra spanning optical to X-ray to gamma-ray bands can be used to probe diffusive acceleration in relativistic, oblique, magnetohydrodynamic (MHD) shocks in blazar jets. Diagnostics on the MHD turbulence near such shocks are obtained using thermal and non-thermal particle distributions resulting from detailed Monte Carlo simulations of DSA. These probes are afforded by the characteristic property that the synchrotron vF(sub v), peak energy does not appear in the gamma-ray band above 100 MeV. We investigate self-consistently the radiative synchrotron and inverse Compton signatures of the simulated particle distributions. Important constraints on the diffusive mean free paths of electrons, and the level of electromagnetic field turbulence are identified for three different case study blazars, Mrk 501, BL Lacertae and AO 0235+164. The X-ray excess of AO 0235+164 in a flare state can be modelled as the signature of bulk Compton scattering of external radiation fields, thereby tightly constraining the energy-dependence of the diffusion coefficient for electrons. The concomitant interpretations that turbulence levels decline with remoteness from jet shocks, and the probable significant role for non-gyroresonant diffusion, are posited.

Baring, Matthew G.↗
NASA NTRS1996

X-Ray Photoemission Measurements of La(1-x)Ca(x)CoO3(x = 0, 0.5)

X-ray photoemission measurements of the core levels and valence electronic structure of LaCoO3 and La(0.5)Ca(0.5)CoO3 high quality epitaxial films are presented. Shifts of the core levels and main valence band features are consistent with a doping-induced change in the chemical potential. Oxygen states are found to significantly contribute to a peak in the valence band at 1 eV binding energy, verifying earlier results of cluster calculations. A Fermi level crossing of this same band upon doping is observed, yielding a high Fermi level density of states.

Vasquez, R. P.↗
NASA NTRS1974

Ac electronic tunneling at optical frequencies

Rectification characteristics of non-superconducting metal-barrier-metal junctions deduced from electronic tunneling have been observed experimentally for optical frequency irradiation of the junction. The results provide verification of optical frequency Fermi level modulation and electronic tunneling current modulation.

Faris, S. M.↗
NASA NTRS1982

Current oscillations in semi-insulating GaAs associated with field-enhanced capture of electrons by the major deep donor EL2

Current oscillations thermally activated by the release of electrons from deep levels in undoped semiinsulating GaAs were observed for the first time. They were attributed to electric field-enhanced capture of electrons by the dominant deep donor EL2 (antisite AsGa defect). This enhanced capture is due to the configurational energy barrier of EL2, which is readily penetrated by hot electrons.

Kaminska, M.↗
NASA NTRS1980

Experimental and theoretical investigations of the quality factor for N/+/P silicon solar cells

Many N(+)P silicon solar cells made with silicon from different growth techniques have current-voltage relations of the form: I = I(0) (exp(qV/AkT) - 1), where the quality factor A is nonintegral, is greater than 1, and shows a temperature dependence. The dark forward characteristics of such cells have been measured over a range of temperatures and the behavior of the factor A derived from them. Lack of agreement with previous models has led to the development of a new model, in which N(+) conduction electrons tunnel to deep levels near that side, these levels being due to junction contamination by impurities. Electron recombination then occurs with holes thermally assisted into the junction from the P side. This mechanism involves increased I(0) values over those for diffusion diode processes and thus reduces the cell power conversion efficiency.

Garlick, G. F. J.↗
NASA NTRS1986

Compton scattering in strong magnetic fields

The relativistic cross section for Compton scattering by electrons in strong magnetic fields is derived. The results confirm and extend earlier work which has treated only transitions to the lowest or first excited Landau levels. For the teragauss field strengths expected in neutron star magnetospheres, the relative rates for excited state transitions are found to be significant, especially for incident photon energies several times the cyclotron frequency. Since these transitions must result in the rapid emission of one or more cyclotron photons as well as the Compton-scattered photon, the scattering process actually becomes a photon 'splitting' mechanism which acts to soften hard photon spectra, and also provides a specific mechanism for populating higher Landau levels in the electron distribution function. The results should be significant for models of gamma-ray bursters and pulsating X-ray sources.

Daugherty, Joseph K.↗
NASA NTRS2016

Electrostatic Discharge Testing of Carbon Composite Solar Array Panels for NASA's Planned Europa Mission to Jupiter

The next planned NASA mission to visit Jupiter is known as the Europa Mission. The objective of this mission concept is to enter orbit around Jupiter in order to conduct multiple close flybys of the icy moon Europa. After careful trade studies, the mission designers have selected solar arrays as the baseline power system for the proposed mission rather than more traditional radioisotope thermoelectric generators. In order to examine the risk of using solar arrays, a series of tests were devised to determine the response of a typical solar array coupon to energetic electrons. Test coupons were fabricated and exposed to electrons ranging from 10 keV to 100 keV, at 1 nA/cm2, while being held at both room and cryogenic temperatures and exposed to end of mission radiation levels. While under electron bombardment, electrical discharges were observed and recorded with the majority of discharges occurring with electron energies of 25 keV. The largest effects on discharge size and rate were the decrease in temperature and the reduction of dielectric material on the sample surface. These tests indicate that solar array panels could be used by the planned Europa Mission in the Jovian environment, but that electrostatic discharges could be expected on the carbon composite solar arrays.

carbon composite↗
NASA NTRS1990

Pressure and current balance conditions during electron beam injections from spacecraft

Electrostatic charging level of a conducting surface in response to injections of electron beams into space plasma is investigated by means of one-dimensional Vlasov code. Injections of Maxwellian beams into a vacuum shows that the surface can charge up to an electric potential phi sub s greater than W sub b, where W sub b is the average electron beam energy. Since Maxwellian beams have extended trails with electrons having energies greater than W sub b, it is difficult to quantify the charging level in terms of the energies of the injected electrons. In order to quantitatively understand the charging in excess of W sub b, simulations were carried out for water-bag types of beam with velocity distribution functions described by f(V) = A for V sub min approx. less than V approx. less than V sub max and f(V) = O otherwise, where A is a constant making the normalized beam density unity. It is found that V sub max does not directly determine the charging level. The pressure distribution in the electron sheath determines the electric field distribution near the surface. The electric field in turn determines the electrostatic potential of the vehicle. The pressure distribution is determined by the beam parameters such as the average beam velocity and the velocity spread of the beam.

Hwang, K. S.↗
NASA NTRS1983

NMR studies of electronic structure in crystalline and amorphous Zr2PdH/x/

The proton Knight shifts and spin-lattice relaxation times have been measured in crystalline and amorphous Ze2PdH(x). Core polarization from the Zr d-band dominates the proton hyperfine interactions. The density of Fermi level d-electron states is reduced in the amorphous phase relative to the electron density in crystalline Zr2PdH(x).

Bowman, R. C., Jr.↗
NASA NTRS1991

The Space Telescope imaging spectrograph 2048 CCD and its characteristics

Development of a 2048-squared CCD for a second-generation Space Telescope instrument has produced some very encouraging devices. The first experimental lot of 10 devices have very few defects, dark currents of less than 40 electrons/pixel/hour at -80 C, readout noise levels of less than 4 electrons rms and excellent charge transfer efficiency at signal levels of less than 10 electrons.

Delamere, W. A.↗
NASA NTRS1992

CCDs and photon counting devices: Applications in space and from the ground

The development of the 2048 by 2048 CCD (Charge Coupled Device) for a second generation space telescope instrument has resulted in devices with very few defects, dark currents of less than 12 electrons/pixel/hour at -80 deg, readout noise levels of less than 4 electrons rms, and excellent charge transfer efficiency at signal levels of less than 10 electrons. A second generation of devices that capitalize on these characteristics have been produced and are currently in test. Faster frame transfer devices that preserve these characteristics have been designed that include tridirectional taps in the serial register. The state of the art in CCD's as photon counting detectors is reviewed.

Delamere, W. A.↗
NASA NTRS1973

Photoionization branching ratios and vibrational intensity distribution for N2, CO; and CO2 between 53 and 75 nm

The probability of radiation producing ions in specific electronic and vibrational levels was documented. For example, when a narrow band-pass of solar ionizing photons is incident on an atmospheric species it is now possible to describe, accurately, how the radiant energy is shared among the various electronic states of the ions produced. The molecules studied were N2, CO, and CO2. These molecules were photoionized by radiation between 53 and 75 nm. The effects of autoionization are discussed and continuum vibrational intensities are tabulated and compared with theoretical Franck-Condon factors where available. The branching ratios and partial cross sections for ionization into various electronic states are tabulated.

Samson, J. A. R.↗
NASA NTRSDate not supplied

Microbes Share Rides Too: Updating Encapsulated Bioburden Estimate Values in Electronic Parts Common to Class D Missions

As NASA develops more planetary protection missions that are Category III and in the Class D/rideshare mission platform, there is an increasing reliance on estimation of prelaunch bioburden to understand needs for burn up and breakup analyses or other methods to meet pre-launch bioburden levels. Current levels estimated for the encapsulated bioburden of semiconductor parts cited by NASA have been based on estimates of semiconductor manufacturing approaches from the 1970s that do not incorporate the evolving cleanliness of semiconductor manufacturing since that time. This investigation will focus on direct sampling of semiconductor parts for encapsulated bioburden values, drawing upon Goddard’s strength in EEE parts, supply chain management, destructive parts analysis and existing local planetary protection lab facilities to prepare and measure encapsulated bioburden at a statistically significant level for standard electronics parts common to known Class D/rideshare platforms.

planetary protection↗
NASA NTRSDate not supplied

Microbes Share Rides Too: Updating Encapsulated Bioburden Estimate Values in Electronic Parts Common to Class D Mission Platforms.

As NASA develops more planetary protection missions that are Category III and in the Class D/rideshare mission platform, there is an increasing reliance on estimation of prelaunch bioburden to understand needs for burn up and breakup analyses or other methods to meet pre-launch bioburden levels. Current levels estimated for the encapsulated bioburden of semiconductor parts cited by NASA have been based on estimates of semiconductor manufacturing approaches from the 1970s that do not incorporate over fifty years of evolving cleanliness of semiconductor manufacturing processes and facilities. This investigation will focus on direct sampling of semiconductor parts for encapsulated bioburden values, drawing upon Goddard’s strength in EEE parts, supply chain management, destructive parts analysis and existing local planetary protection lab facilities to prepare and measure encapsulated bioburden at a statistically significant level for standard electronics parts common to known Class D/rideshare platforms.

planetary protection↗
NASA NTRS1983

Electron collisional rate coefficients for low-level transitions in hydrogen

There exists presently no general agreement concerning the collisional excitation rates of atomic hydrogen. The present investigation is concerned with the results reported by various investigators, taking into account the semiempirical rates of Johnson (1972), a study conducted by Aggarwal (1983), empirically based rates of Crandall et al. (1974), and the rates tabulated in Osterbrock (1974), based on the close-coupling calculations of Burke et al. (1967). It is found that there is a major conflict between the 'best' theoretical and Johnson values on the one hand, and the empirical data on the other. A study of the data shows that the Johnson value for the 1 to 2 rate agrees well with other theoretical calculations, and within 25 percent of empirical measurements, but that the Johnson 1 to 3 rate is 40-75 percent of the 'best' theoretical calculations.

Drake, S. A.↗