Physical Sciences

Depth-Penetrating Luminescence Thermography of Thermal-Barrier Coatings

Temperatures at depths can be measured by luminescence decay of suitable thermographic phosphors.

Posted in: Physical Sciences, Briefs, TSP

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Automated Counting of Particles To Quantify Cleanliness

A machine vision system, similar to systems used in microbiological laboratories to count cultured microbes, has been proposed for quantifying the cleanliness of nominally precisely cleaned hardware by counting residual contaminant particles. The system would include a microscope equipped with an electronic camera and circuitry to digitize the camera output, a personal computer programmed with machine-vision and interface software, and digital storage media.

Posted in: Physical Sciences, Briefs

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Compact Infrasonic Windscreen

High values of infrasound-transmission and wind-noise-attenuation coefficients can be realized. A compact windscreen has been conceived for a microphone of a type used outdoors to detect atmospheric infrasound from a variety of natural and man-made sources. Wind at the microphone site contaminates received infrasonic signals (defined here as sounds having frequencies <20 Hz), because a microphone cannot distinguish between infrasonic pressures (which propagate at the speed of sound) and convective pressure fluctuations generated by wind turbulence. Hence, success in measurement of outdoor infrasound depends on effective screening of the microphone from the wind.

Posted in: Physical Sciences, Briefs

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Laser Metrology for an Optical-Path- Length Modulator

Sensitivity is of the order of picometers. Laser gauges have been developed to satisfy requirements specific to monitoring the amplitude of the motion of an optical path- length modulator that is part of an astronomical interferometer. The modulator includes a corner-cube retroreflector driven by an electromagnetic actuator. During operation of the astronomical interferometer, the electromagnet is excited to produce linear reciprocating motion of the corner-cube retroreflector at an amplitude of 2 to 4 mm at a frequency of 250, 750, or 1,250 Hz. Attached to the corner- cube retroreflector is a small pick-off mirror. To suppress vibrations, a counterweight having a mass equal to that of the corner-cube retroreflector and pick-off mirror is mounted on another electromagnetic actuator that is excited in opposite phase.

Posted in: Physical Sciences, Briefs, TSP

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PCM Passive Cooling System Containing Active Subsystems

A PCM would absorb intense heat bursts and would be regenerated between them. A multistage system has been proposed for cooling a circulating fluid that is subject to intermittent intense heating. The system would be both flexible and redundant in that it could operate in a basic passive mode, either sequentially or simultaneously with operation of a first, active cooling subsystem, and either sequentially or simultaneously with a second cooling subsystem that could be active, passive, or a combination of both. This flexibility and redundancy, in combination with the passive nature of at least one of the modes of operation, would make the system more reliable, relative to a conventional cooling system.

Posted in: Physical Sciences, Briefs

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Automated Electrostatics Environmental Chamber

Atmospheric temperature and pressure can be varied between the extremes of Mars and Earth. The Mars Electrostatics Chamber (MEC) is an environmental chamber designed primarily to create atmospheric conditions like those at the surface of Mars to support experiments on electrostatic effects in the Martian environment. The chamber is equipped with a vacuum system, a cryogenic cooling system, an atmospheric-gas replenishing and analysis system, and a computerized control system that can be programmed by the user and that provides both automation and options for manual control. The control system can be set to maintain steady Mars-like conditions or to impose temperature and pressure variations of a Mars diurnal cycle at any given season and latitude. In addition, the MEC can be used in other areas of research because it can create steady or varying atmospheric conditions anywhere within the wide temperature, pressure, and composition ranges between the extremes of Mars-like and Earth-like conditions.

Posted in: Physical Sciences, Briefs

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One-Dimensional Photonic Crystal Superprisms

In comparison with three-dimensional superprisms, these could be fabricated more easily.

Posted in: Physical Sciences, Photonics, Briefs

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