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Precision Detector Conductance Definition via Ballistic Thermal Transport

This innovation could be applied in the development of bolometric detector array sensors. Goddard Space Flight Center, Greenbelt, Maryland The characteristics of a thermal detector, such as sensitivity, response time, and saturation power (or energy resolution), are functions of the thermal conductance of the detector to its cryogenic environment. The thermal conductance is specified to achieve a tradeoff among the highest sensitivity, allowed response time, and the desired saturation energy or power budget for the particular application. It is essential to achieve the design thermal conductance (within an acceptable variance) after a thermal detector has been fabricated. Otherwise, the detector will fail to achieve its desired functionality. In addition, the formation of a multi-pixel imaging array becomes difficult and costly when the design thermal conductance is not achieved with high post-fabrication yield.

Posted in: Briefs, TSP, Manufacturing & Prototyping, Sensors

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Thermal Spraying of Coatings Using Resonant Pulsed Combustion

This is a high-volume, high-velocity surface deposition of protective metallic and other coatings on surfaces. John H. Glenn Research Center, Cleveland, Ohio Thermal spray coating is not a new process. There are different techniques utilized that depend on the objective function of the coating, the environment to which the coated piece will be subjected, and the coating material used. In any application, quality is ultimately measured by how well the coating material adheres to the sprayed surface. This, in turn, is controlled by the velocity at which the coating material impinges on the substrate, the size of the molten coating particles, and the degree to which the coating material is prevented from chemically reacting while in a molten state.

Posted in: Briefs, TSP, Manufacturing & Prototyping

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In-Situ Mixing, Degassing, Decavitation, and Extrusion Modules for Fused Deposition Modeling 3D Printers

A resonant acoustics mixing mechanism equipped with high-vacuum pulling capacity will be employed. John H. Glenn Research Center, Cleveland, Ohio Additively manufactured 3D articles of certain high-temperature polymer composites such as ULTEM 1000 reinforced with chopped carbon fibers and printed by current state-of-the-art Fused Deposition Modeling (FDM) printers, suffer significantly with high porosity due to moisture-induced cavitation during the liquefying process under high printing temperatures because the pre-fabricated feedstock filaments contain excessive moisture trapped in polymer matrix or fiber interfaces that is extremely difficult to remove. During compounding (mixing of chopped fibers with resin) and the filament extrusion process, controlling moisture absorption is extremely difficult and very costly. Furthermore, compounding and filament fabrication are two separate processes normally performed at different plants, and thus add extra costs and technical challenge of keeping the material dry. In the case of the high-temperature polymer, it is even more difficult to control the residual moisture content and is more prone to blistering during FDM printing due to higher melting temperature.

Posted in: Briefs, TSP, Manufacturing & Prototyping

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Stable, Flat Packaging Concepts for Large Detector Arrays

Applications include packing of back-illuminated and delta-doped arrays without damage to sensitive surfaces. NASA’s Jet Propulsion Laboratory, Pasadena, California A ceramic vacuum chuck is used to hold large detector arrays flat while being attached parallel to a rigid substrate. Once held in the vacuum chuck, the component is typically seized by epoxy against a rigid substrate. The problem that interferes with this operation happens when the epoxy spreads to places where it is not wanted, even into the gap between the component and its vacuum chuck, and over electrical contacts that are intended for wire bonding.

Posted in: Briefs, TSP, Manufacturing & Prototyping

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Dual-Polarized W-Band Metal Patch Antenna Element for Phased Array Applications

Interlaced transmit/receive all-metal patch elements eliminate the need for discrete isolators and increase efficiency. NASA’s Jet Propulsion Laboratory, Pasadena, California W-band active phased array antennas have a very small inter-element pitch (≈2 mm). In this innovation, instead of trying to integrate isolators into the unit cell to separate transmit and receive signals, an interlaced triangular grid of metal patch elements has been developed. The isolation between transmit elements and receive elements has been demonstrated to be on the order of 25 dB or more, precluding the need for discrete isolator circuits. Using metal patch technology, the element and associated interconnect loss has been demonstrated to be 0.5 dB at 94 GHz, which represents an efficiency of 89%.

Posted in: Briefs, TSP, Manufacturing & Prototyping

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Uniformly Etched Lateral Gratings Applied to Pre-existing Ridge Waveguides

New technology is 100 times smaller and has fewer components with possibly the same performance. NASA’s Jet Propulsion Laboratory, Pasadena, California There is great difficulty in implementing lateral gratings in GaSb-based lasers. Commercially, single-frequency GaSb lasers have been fabricated using metal gratings deposited laterally to the ridge-waveguide (RWG) stripe. The disadvantage of this is that the laser performance is compromised by additional optical loss due to radiation absorption by the metal. Fabricating lasers in this way limits the potential for high-power performance. A better method is to etch gratings into the semiconductor, but generally, patterning these grating structures is difficult because of nonuniformity of the grating pattern and etching difficulty due to sub-micrometer dimensions.

Posted in: Briefs, TSP, Manufacturing & Prototyping

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High-Precision Thin Film Metal Liftoff Technique

This process can be used by industries that need to fabricate microelectronic devices and superconducting sensors. Goddard Space Flight Center, Greenbelt, Maryland The objective of this work was to develop a thin film metal liftoff process that would allow one to accurately pattern two-micron-wide (or wider) features. The goal of this innovation was to pattern thin metal films on silicon substrates. The thin metal films can be deposited using physical vapor deposition techniques. The metallic films to be lifted off were deposited via DC magnetron sputtering, in which the mean free path of the metal atoms to be deposited is on the order of one micron. Thus, the deposited metal could conformally coat structures to fill in gaps that were greater than approximately one micron tall.

Posted in: Briefs, TSP, Manufacturing & Prototyping

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