Physical Sciences

Measuring Two Key Parameters of H3 Color Centers in Diamond

These parameters are needed for the further development of diamond lasers. A method of measuring two key parameters of H3 color centers in diamond has been created as part of a continuing effort to develop tunable, continuouswave, visible lasers that would utilize diamond as the lasing medium. (An H3 color center in a diamond crystal lattice comprises two nitrogen atoms substituted for two carbon atoms bonded to a third carbon atom. H3 color centers can be induced artificially; they also occur naturally. If present in sufficient density, they impart a yellow hue.) The method may also be applicable to the corresponding parameters of other candidate lasing media. One of the parameters is the number density of color centers, which is needed for designing an efficient laser. The other parameter is an optical-absorption cross section, which, as explained below, is needed for determining the number density

Posted in: Physical Sciences, Briefs

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Dusty-Plasma Particle Accelerator

Microparticles and nanoparticles can be accelerated to controllable kinetic energies.

Posted in: Physical Sciences, Briefs

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Ferroelectric Devices Emit Charged Particles and Radiation

Compact, lightweight, low-power sources could be useful in numerous applications.

Posted in: Physical Sciences, Briefs, TSP

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Shock Waves in a Bose-Einstein Condensate

A paper presents a theoretical study of shock waves in a trapped Bose-Einstein condensate (BEC).

Posted in: Physical Sciences, Briefs, TSP

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Thermal Imaging of Earth for Accurate Pointing of Deep-Space Antennas

A report discusses a proposal to use thermal (long-wavelength infrared) images of the Earth, as seen from spacecraft at interplanetary distances, for pointing antennas and telescopes toward the Earth for Ka-band and optical communications.

Posted in: Physical Sciences, Briefs, TSP

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Ester-Based Electrolytes for Low- Temperature Li-Ion Cells

Electrolytes comprising LiPF6 dissolved at a concentration of 1.0 M in five different solvent mixtures of alkyl carbonates have been found to afford improved performance in rechargeable lithium-ion electrochemical cells at temperatures as low as -70° C. These and other electrolytes have been investigated in continuing research directed toward extending the lower limit of practical operating temperatures of Li-ion cells. This research at earlier stages, and the underlying physical and chemical principles, were reported in numerous previous NASA Tech Briefs articles, the most recent being “Low-ECContent Electrolytes for Low-Temperature Li-Ion Cells” (NPO-30226), NASA Tech Briefs, Vol. 27, No. 1 (January 2003), page 46. The ingredients of the present solvent mixtures are ethylene carbonate (EC), ethyl methyl carbonate (EMC), methyl butyrate (MB), methyl propionate (MP), ethyl propionate (EP), ethyl butyrate (EB), and ethyl valerate (EV). In terms of volume proportions of these ingredients, the present solvent mixtures are

Posted in: Physical Sciences, Briefs, TSP

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Hygrometer for Detecting Water in Partially Enclosed Volumes

This portable instrument samples humid air from difficult-toreach spaces.A portable hygrometer has been devised to implement a pre-existing technique for detecting water trapped in partially enclosed volumes that may be difficult to reach and cannot be examined directly. The technique is based on the fact that eventually the air in such a volume becomes saturated or nearly so. The technique is straightforward: One measures the relative humidity and temperature of both the ambient air and a sample of air from the enclosed volume. If the relative humidity of the sample is significantly greater than that of the ambient air and/or if the sample is at or close to the dew point, then it can be concluded that water is trapped in the volume. Of course, the success of this technique depends on the existence of an access hole through which one can withdraw some air from the enclosed volume.

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