SEARCH · Engineering Papers
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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Antenna is simultaneously resonant at 8.75 MHz, 11.825 MHz, and 20.562 MHz. It provides a near-field radiator which has a constant current distribution across its radiating elements for each of the resonant frequencies.
Method of calculating Breit-Wigner resonance parameters for uranium 233 allows for different sources of data. Parameters for 63 resonances in the neutron-energy range 0 to 62 eV are yielded by simultaneous fit to three sets of data.
Error analysis of resonant orbits for geodesy, discussing high order geopotential coefficient recovery by resonance and gravity model errors
Alouette 1 plasma resonance observations, analyzing electron density measurements in sheath region and cyclotron harmonic resonant frequencies
Tonks-Dattner resonances in warm inhomogeneous plasma column, examining kinetic theory for waveform shapes and resonance location
Apollo 11 lunar fines, rocks and breccias luminescence, electron paramagnetic resonance and optical properties, discussing reflection spectra, heating effects and dipole resonance
Subsidiary resonance response time decay behavior in ionosphere, showing occurrence of principal resonances at higher orders
Compact and easy to use solid state nuclear magnetic resonance detector is designed for measuring field strength to 20 teslas in cryogenically cooled magnets. Extremely low noise and high sensitivity make detector applicable to nearly all types of analytical nuclear magnetic resonance measurements and can be used in high temperature and radiation environments.
New type cavity resonator is designed for hydrogen maser. Resonator consists of three pieces of glass-ceramic material having extremely low thermal coefficient of expansion and provides very stable mechanical tuning.
An approach to stabilizing control systems is presented which structures controllers like passive mechanical systems. The controller is visualized as a structural part with a passive behavior similar to springs, dashpots, and masses. If such a controller is connected by a proper feedback arrangement, then a passive mechanical plant cannot upset stability, regardless of masses, resonances, and three-dimensional coupling. The concept of resonance-inert stabilization is explained by structuring the controller of a simple feedback loop. Reactive functions, connections, and matrices are defined and used in the stabilization concept. The realization of a possible Skylab control system is discussed and compared with the present design. This example demonstrates the applicability to three-dimensional problems with lagging controllers.
Near resonance charge exchange between ions of a large ionization potential gas such as helium or neon and vapors of metals such as zinc, cadmium, selenium, or tellurium has produced laser action in the metal ion gas. The possibility of obtaining population inversions in near resonant charge exchange systems (Xe-Ca, Xe-Mg, Xe-Sr, Xe-Ba, Ar-Mg, N-Ca) was investigated. The analysis is an initial value problem that utilizes rate equations for the densities of relevant levels of the laser gas (Ca, Ba, Mg, or Sr) and an electron energy equation. Electron excitation rates are calculated using the Bohr-Thomson approximation for the cross section. Approximations to experimental values of the electron ionization cross section and the ion-atom charge exchange cross section are used. Preliminary results have been obtained for the Ca-Xe system and show that it is possible to obtain gains greater than 10 to the 14th power/m with inversion times up to 8x10 to the minus 7th power second. A possible charge exchange laser system using a MPD arc plasma accelerator is also described.
An interpretation of the sequence of diffuse plasma resonances observed by space probes (Alouette 2 and ISIS-1 satellites) is developed in terms of wave-particle nonlinear interaction in a weakly turbulent plasma including the electrostatic electron cyclotron harmonic wave instability. The longest time duration of the center frequency of the diffuse plasma resonance is found to coincide with the most favorable condition for the electrostatic electron cyclotron harmonic wave instability which is obtained by solving the dispersion equation obtained for a linear approximation of the kinetic wave equation for the warm magnetoactive plasma. The electrostatic field due to the transmission of the intense rf pulse produces plasma turbulence involving nonlinear wave-wave interaction and temperature anisotropy which leads to instability. This instability supplies energy to the turbulence. The process can be thought of as a feedback system.
Description of an experimental dual resonant cavity absorption cell for observing microwave spectroscopic double-resonance effects. The device is composed of two Fabry-Perot interferometers excited by independent microwave sources and mounted at right angles in a suitable vacuum enclosure. The pumping transition is modulated by one source and the modulation induced on the rf absorption in the orthogonal cavity is detected.
Rocket measurements of the differential photoelectron flux and the volume emission rate of the N2(0, 0) second positive band are used to calculate the daytime concentration of metastable A(super 3)Sigma(sub u)+ molecules, and consequently the resonance scattering contribution to the N2 first positive emission in the dayglow. The dominant source of N2 first positive emission is found to be photoelectron impact, with resonance scattering contributing only 10-20 per cent the total emission.
Using the water-bag model of an electron plasma the nonlinear interaction of two plasma wave pulses (each of sufficiently narrow wave-number spectrum) is discussed. It is shown that for the special case of a resonant (zero group velocity) pulse interacting with a nonresonant pulse, the interaction produces an effective slowing down of the group velocity of the nonresonant pulse. An application of this theory to the explanation of the apparent resonances at fractions of the plasma frequency observed in the ionosphere is discussed.
The variation of resonant time duration with latitude, altitude, and fn/fh has been determined for the plasma resonances observed by Alouette I and Alouette II at the electron plasma frequency fn, the electron cyclotron frequency fh, the upper hybrid frequency ft, and the harmonics n-fh where n = 2,3
Consideration of the application of the measurement of resonance fluorescence radiation excited by tunable laser radiation to the detection of atomic, molecular, and ionic species in the upper atmosphere. The species considered are N2, N2(+), NO, NO(+), O2(+), CO, CO(+), CH, Na, K, and Ca. Calculations of the resonance scattering cross sections, photon returns, and signal-to-noise ratios are given for these species for a range of conditions. Based on a probing altitude of 100 km, the detections of N2, NO, CO, CH, O2, and the trace metals appear feasible with state-of-the-art systems and within the concentration range present in the atmosphere.
Calculation of the angular dependence of the intensity of solar Lyman alpha resonantly scattered from neutral interstellar hydrogen which has penetrated the solar system. A simple model which essentially neglects temperature effects, but which includes gravity, radiation pressure, photoionization and charge exchange is used for this calculation. The results are then compared with the observations. The resonant scattering of He I 584 A is also treated.