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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.

Posted in: Physical Sciences, Briefs

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Radio-Frequency Plasma Cleaning of a Penning Malmberg Trap

This method is superior to cleaning by baking. Radio-frequency-generated plasma has been demonstrated to be a promising means of cleaning the interior surfaces of a Penning-Malmberg trap that is used in experiments on the confinement of antimatter. Cleaning of the interior surfaces is necessary to minimize numbers of contaminant atoms and molecules, which reduce confinement times by engaging in matter/ antimatter-annihilation reactions with confined antimatter particles.

Posted in: Physical Sciences, Briefs

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Precision Cryogenic Dilatometer

A dilatometer based on a laser interferometer is being developed to measure mechanical creep and coefficients of thermal expansion (CTEs) of materials at temperatures ranging from ambient down to 15 K. This cryogenic dilatometer has been designed to minimize systematic errors that limit the best previously available dilatometers. At its prototype stage of development, this cryogenic dilatometer yields a strain measurement error of 35 ppb or 1.7 ppb/K CTE measurement error for a 20-K thermal load, for low-expansion materials in the temperature range from 310 down to 30 K. Planned further design refinements that include a provision for stabilization of the laser and addition of a high-precision sampleholding jig are expected to reduce the measurement error to 5-ppb strain error or 0.3-ppb/K CTE error for a 20-K thermal load.

Posted in: Physical Sciences, Briefs, TSP

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Stroboscopic Interferometer for Measuring Mirror Vibrations

Interferometric snapshots are taken at intervals over a cycle for each vibrational mode.Stroboscopic interferometry is a technique for measuring the modes of vibration of mirrors that are lightweight and, therefore, unavoidably flexible. The technique was conceived especially for modal characterization of lightweight focusing mirror segments to be deployed in outer space; however, the technique can be applied to lightweight mirrors designed for use on Earth as well as the modal investigation of other optical and mechanical structures.

Posted in: Physical Sciences, Briefs

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Spill-Resistant Alkali-Metal-Vapor Dispenser

This dispenser can be used in a gravitational or non-gravitational environment.  A spill-resistant vessel has been developed for dispensing an alkali-metal vapor. Vapors of alkali metals (most commonly, cesium or rubidium, both of which melt at temperatures slightly above room temperature) are needed for atomic frequency standards, experiments in spectroscopy, and experiments in laser cooling. Although the present spill-resistant alkali-metal dispenser was originally intended for use in the low-gravity environment of outer space, it can also be used in normal Earth gravitation: indeed, its utility as a vapor source was confirmed by use of cesium in a ground apparatus.

Posted in: Physical Sciences, Briefs, TSP

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Improved Compression of Wavelet-Transformed Images

Code parameters are selected adaptively to achieve high compression performance.  A recently developed data-compression method is an adaptive technique for coding quantized wavelet-transformed data, nominally as part of a complete image-data compressor. Unlike some other approaches, this method admits a simple implementation and does not rely on the use of large code tables.

Posted in: Physical Sciences, Briefs

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Flexible Heater Provides Thermal Solution for Fast Temperature-Cycling Environments

Uniformity and tight dimensional tolerances provide flexibility for smaller, more robust heating components. Thermal components for military, aerospace, and medical applications are continually getting smaller, more accurate, and more robust. To match these technological advancements, heating systems are being custom-designed to provide critical edgeto- edge uniformity, tight dimensional tolerances, and integrated sensors and flex leads to create complete thermal solutions.

Posted in: Physical Sciences, Briefs

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