Tech Briefs

Making AlNx Tunnel Barriers Using a Low-Energy Nitrogen-Ion Beam

Ion-beam parameters can be controlled to optimize properties of AlNx layers. A technique based on accelerating positive nitrogen ions onto an aluminum layer has been demonstrated to be effective in forming thin (<2 nm thick) layers of aluminum nitride (AlNx) for use as tunnel barriers in Nb/Al-AlNx/Nb superconductor/ insulator/ superconductor (SIS) Josephson junctions. AlNx is the present material of choice for tunnel barriers because, to a degree greater than that of any other suitable material, it offers the required combination of low leakage current at high current density and greater thermal stability.

Posted in: Briefs, Semiconductors & ICs


Making Wide-IF SIS Mixers With Suspended Metal-Beam Leads

Devices are fabricated on SOI substrates by use of silicon-micromachining techniques. A process that employs silicon-on-insulator (SOI) substrates and silicon (Si) micromachining has been devised for fabricating wide intermediate frequency band (wide-IF) superconductor/ insulator/ superconductor (SIS) mixer devices that result in suspended gold beam leads used for radio-frequency grounding. The mixers are formed on 25-µm-thick silicon membranes. They are designed to operate in the 200 to 300 GHz frequency band, wherein wide-IF receivers for tropospheric- chemistry and astrophysical investigations are necessary. The fabrication process can be divided into three sections:

Posted in: Briefs, TSP, Semiconductors & ICs


Rugged Iris Mechanism

Advantages include capability for full obscuration, low friction, and general adaptability of design. A rugged iris mechanism has been designed to satisfy several special requirements, including a wide aperture in the “open” position, full obscuration in the “closed” position, ability to function in a cryogenic or other harsh environment, and minimization of friction through minimization of the number of components. An important element of the lowfriction aspect of the design is maximization of the flatness of, and provision of small gaps between, adjacent iris blades. The tolerances of the design can be very loose, accommodating thermal expansions and contractions associated with large temperature excursions. The design is generic in that it is adaptable to a wide range of aperture sizes and can be implemented in a variety of materials to suit the thermal, optical, and mechanical requirements of various applications.

Posted in: Briefs, Mechanical Components, Mechanics


Alignment Stage for a Cryogenic Dilatometer

A low-friction, low-thermal-expansion kinematic design affords stability and precise adjustability. A three degree of freedom alignment stage has been designed and built for use in a cryogenic dilatometer that is used to measure thermal strains. The alignment stage enables precise adjustments of the positions and orientations of optical components to be used in the measurements and, once adjustments have been completed, keeps the components precisely aligned during cryogenic dilatometer operations that can last as long as several days.

Posted in: Briefs, TSP, Mechanical Components


Generating Solid Models From

Topographical Data Topographical data are converted into forms useable by rapid-prototyping machines.A method of generating solid models of terrain involves the conversion of topographical data into a form useable by a rapid-prototyping (RP) machine. The method was developed to enable the use of the RP machine to make solid models of Martian terrain from Mars Orbiter laser-altimeter topographical data. The method is equally applicable to the generation of models of the terrains of other astronomical bodies, including other planets, asteroids, and Earth.

Posted in: Briefs, TSP, Information Sciences


Computationally Lightweight Air-Traffic-Control Simulation

This algorithm simulates ATC functions for a busy airport.An algorithm for computationally lightweight simulation of automated airtraffic control (ATC) at a busy airport has been derived. The algorithm is expected to serve as the basis for development of software that would be incorporated into flight-simulator software, the ATC component of which is not yet capable of handling realistic airport loads. Software based on this algorithm could also be incorporated into other computer programs that simulate a variety of scenarios for purposes of training or amusement.

Posted in: Briefs, TSP, Information Sciences


Low-Density, Aerogel-Filled Thermal- Insulation Tiles

Aerogel fillings have been investigated in a continuing effort to develop low-density thermal-insulation tiles that, relative to prior such tiles, have greater dimensional stability (especially less shrinkage), equal or lower thermal conductivity, and greater strength and durability. In preparation for laboratory tests of dimensional and thermal stability, prototypes of aerogel-filled versions of recently developed low-density tiles have been fabricated by impregnating such tiles to various depths with aerogel formations ranging in density from 1.5 to 5.6

Posted in: Briefs, Materials


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