Elemental analyses of lunar samples by 14 MeV and thermal neutron activation Final report, period ending 31 Jan. 1971

Neutron activation analyses of lunar sample abundance

Development of a hydrogen-oxygen internal combustion engine space power system

Hydrogen-oxygen internal combustion engine space power syste

Thermal contraints on high-pressure granulite metamorphism of supracrustal rocks

The circumstances leading to the formation and exposure at the Earth's surface of supracrustal granulites are examined. These are defined as sediments, volcanics, and other rock units which originally formed at the surface of the Earth, were metamorphosed to high-pressure granulite facies (T = 700-900 C, P = 5-10 kbar), and reexposed at the Earth's surface, in many cases underlain by normal thicknesses of continental crust (30-40 km). Five possible heating mechanisms to account for granulite metamorphism of supracrustal rocks are discussed: magnetic heating, thermal relaxation of perturbed temperature profiles following underthrusting of the continental crust, thermal relaxation after underthrusting of thin slivers of supracrustal rocks below continental crust of normal thickness, major preheating of the upper plate, and shear heating caused by frictional stress along the thrust plane

Novel Dynamical Resonances in Finite-Temperature Bose-Einstein Condensates

We describe a variety of intriguing mode-coupling effects which can occur in a confined Bose-Einstein condensed system at finite temperature. These arise from strong interactions between a condensate fluctuation and resonances of the thermal cloud yielding strongly non-linear behaviour. We show how these processes can be affected by altering the aspect ratio of the trap, thereby changing the relevant mode-matching conditions. We illustrate how direct driving of the thermal cloud can lead to significant shifts in the excitation spectrum for a number of modes and provide further experimental scenarios in which the dramatic behaviour observed for the $m=0$ mode at JILA (Jin {\it et al.} 1997) can be repeated. Our theoretical description is based on a successful second-order finite-temperature quantum field theory which includes the full coupled dynamics of the condensate and thermal cloud and all relevant finite-size effects

Theory of the cold collision frequency shift in 1S--2S spectroscopy of Bose-Einstein-condensed and non-condensed hydrogen

We show that a correct formulation of the cold collision frequency shift for two photon spectroscopy of Bose-condensed and cold non-Bose-condensed hydrogen is consistent with experimental data. Our treatment includes transport and inhomogeneity into the theory of a non-condensed gas, which causes substantial changes in the cold collision frequency shift for the ordinary thermal gas, as a result of the very high frequency (3.9kHz) of transverse trap mode. For the condensed gas, we find substantial corrections arise from the inclusion of quasiparticles, whose number is very large because of the very low frequency (10.2Hz) of the longitudinal trap mode. These two effects together account for the apparent absence of a "factor of two" between the two possibilities. Our treatment considers only the Doppler-free measurements, but could be extended to Doppler-sensitive measurements. For Bose-condensed hydrogen, we predict a characteristic "foot" extending into higher detunings than can arise from the condensate alone, as a result of a correct treatment of the statistics of thermal quasiparticles.Comment: 16 page J Phys B format plus 6 postscript figure

Cosmic antimatter annihilation and the gamma-ray background spectrum

Cosmic antimatter annihilation and gamma ray background spectru

Radioisotope thermal photovoltaic application of the GaSb solar cell

An examination of a RTVP (radioisotopic thermophotovoltaic) conceptual design has shown a high potential for power densities well above those achievable with radioisotopic thermoelectric generator (RTG) systems. An efficiency of 14.4 percent and system specific power of 9.25 watts/kg were predicted for a system with sixteen GPHS (general purpose heat source) sources operating at 1100 C. The models also showed a 500 watt system power by the strontium-90 isotope at 1200 C at an efficiency of 17.0 percent and a system specific power of 11.8 watts/kg. The key to this level of performance is a high-quality photovoltaic cell with narrow bandgap and a reflective rear contact. Recent work at Boeing on GaSb cells and transparent back GaAs cells indicate that such a cell is well within reach

Project for the analysis of technology transfer Quarterly report, 13 Jul. - 12 Oct. 1968

Statistical characteristics of transfer data bank users, and outline of technology transfer and utilization instruction cours

Parametric down-conversion from a wave-equations approach: geometry and absolute brightness

Using the approach of coupled wave equations, we consider spontaneous parametric down-conversion (SPDC) in the narrow-band regime and its relationship to classical nonlinear processes such as sum-frequency generation. We find simple expressions in terms of mode overlap integrals for the absolute pair production rate into single spatial modes, and simple relationships between the efficiencies of the classical and quantum processes. The results, obtained with Green function techniques, are not specific to any geometry or nonlinear crystal. The theory is applied to both degenerate and non-degenerate SPDC. We also find a time-domain expression for the correlation function between filtered signal and idler fields.Comment: 10 pages, no figure