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Cryogenic Pound Circuits for Cryogenic Sapphire Oscillators

Two modern cryogenic variants of the Pound circuit have been devised to increase the frequency stability of microwave oscillators that include cryogenic sapphire-filled cavity resonators. Invented in the 1940s and named after its inventor (R. V. Pound), the original Pound circuit is a microwave frequency discriminator that provides feedback to stabilize a voltage-controlled microwave oscillator with respect to an associated cavity resonator. Heretofore, Pound circuits used in conjunction with cryogenic resonators have included room-temperature electronic components coupled to the resonators via such inter-connections as coaxial cables. The thermo mechanical instabilities of these inter-connections give rise to frequency instabilities. In a cryogenic Pound circuit of the present improved type, all of the active electronic components, the inter-connections among them, and the inter-connections between them and the resonator reside in the cryogenic environment along with the resonator and, hence, are thermo-mechanically stabilized to a large degree. Hence, further, frequency instabilities are correspondingly reduced.

Posted in: Briefs, TSP

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Making Activated Carbon by Wet Pressurized Pyrolysis

Thermomechanical instabilities and associated frequency instabilities are reduced. A wet pressurized pyrolysis (wet carbonization) process has been invented as a means of producing activated carbon from a wide variety of inedible biomass consisting principally of plant wastes. The principal intended use of this activated carbon is room-temperature adsorption of pollutant gases from cooled incinerator exhaust streams.

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Composite Solid Electrolyte Containing Li+- Conducting Fibers

Li+-ion conductivities are greater than those achieved before. Improved composite solid polymer electrolytes (CSPEs) are being developed for use in lithium-ion power cells. The matrix components of these composites, like those of some prior CSPEs, are highmolecular- weight dielectric polymers [generally based on polyethylene oxide (PEO)]. The filler components of these composites are continuous, highly-Li+- conductive, inorganic fibers.

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Electrically Conductive Anodized Aluminum Surfaces

These coatings are highly adherent, transparent, and relatively inexpensive. Anodized aluminum components can be treated to make them sufficiently electrically conductive to suppress discharges of static electricity. The treatment was conceived as a means of preventing static electric discharges on exterior satin-anodized aluminum (SAA) surfaces of spacecraft without adversely affecting the thermal-control/optical properties of the SAA and without need to apply electrically conductive paints, which eventually peel off in the harsh environment of outer space. The treatment can also be used to impart electrical conductivity to anodized housings of computers, medical electronic instruments, telephone-exchange equipment, and other terrestrial electronic equipment vulnerable to electrostatic discharge.

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Rapid-Chill Cryogenic Coaxial Direct- Acting Solenoid Valve

A commercially available cryogenic direct-acting solenoid valve has been modified to incorporate a rapid-chill feature. In the original application for which this feature was devised, there is a requirement to ensure that at all times, the valve outlet flow consists entirely or mostly of liquid; that is, there is a requirement to minimize vaporization of cryogenic liquid flowing through the valve. This translates to a requirement to chill interior valve surfaces in contact with the flowing liquid.

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Variable-Tension-Cord Suspension/Vibration-Isolation System

Cord tensions are adjusted to optimize vibration-isolation properties. A system for mechanical suspension and vibration isolation of a machine or instrument is based on the use of Kevlar (or equivalent aromatic polyamide) cord held in variable tension between the machine or instrument and a surrounding frame. The basic concept of such a tensioned-cord suspension system (including one in which the cords are made of aromatic polyamide fibers) is not new by itself; what is new here is the additional provision for adjusting the tension during operation to optimize vibration-isolation properties.

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Techniques for Connecting Superconducting Thin Films

Junctions can be tailored to obtain desired levels of electrical resistance. Several improved techniques for connecting superconducting thin films on substrates have been developed. The techniques afford some versatility for tailoring the electronic and mechanical characteristics of junctions between superconductors in experimental electronic devices. The techniques are particularly useful for making superconducting or alternatively normally conductive junctions (e.g., Josephson junctions) between patterned superconducting thin films in order to exploit electron quantum-tunneling effects.

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