Tech Briefs

Electron-Spin Filters Based on the Rashba Effect

Filters would be made from nonmagnetic semiconductors and operated without applied magnetic fields. Semiconductor electron-spin filters of a proposed type would be based on the Rashba effect, which is described briefly below. Electron-spin filters — more precisely, sources of spin-polarized electron currents — have been sought for research on, and development of, the emerging technological discipline of spintronics (spin-based electronics). There have been a number of successful demonstrations of injection of spin-polarized electrons from diluted magnetic semiconductors and from ferromagnetic metals into nonmagnetic semiconductors. In contrast, a device according to the proposal would be made from nonmagnetic semiconductor materials and would function without an applied magnetic field.

Posted in: Briefs, TSP

Read More >>

Diffusion-Cooled Tantalum Hot-Electron Bolometer Mixers

Lower TC s should translate to lower noise and lower required local-oscillator power. A batch of experimental diffusion-cooled hot-electron bolometers (HEBs), suitable for use as mixers having input frequencies in the terahertz range and output frequencies up to about a gigahertz, exploit the superconducting/normal-conducting transition in a thin strip of tantalum. The design and operation of these HEB mixers are based on mostly the same principles as those of a prior HEB mixer that exploited the superconducting/ normal-conducting transition in a thin strip of niobium and that was described in “Diffusion-Cooled Hot-Electron Bolometer Mixer” (NPO-19719), NASA Tech Briefs, Vol. 21, No. 1 (January 1997), page 12a.

Posted in: Briefs, TSP

Read More >>

Improved Position Sensor for Feedback Control of Levitation

In this application, an incandescent light bulb is preferable to a laser. An improved optoelectronic apparatus has been developed to provide the position feedback needed for controlling the levitation subsystem of a containerless processing system. As explained below, the advantage of this apparatus over prior optoelectronic apparatuses that have served this purpose stems from the use of an incandescent lamp, instead of a laser, to illuminate the levitated object.

Posted in: Briefs

Read More >>

Relative-Motion Sensors and Actuators for Two Optical Tables

Relative motions can be suppressed or imposed on demand. Optoelectronic sensors and magnetic actuators have been developed as parts of a system for controlling the relative position and attitude of two massive optical tables that float on separate standard air suspensions that attenuate ground vibrations. In the specific application for which these sensors and actuators were developed, one of the optical tables holds an optical system that mimics distant stars, while the other optical table holds a test article that simulates a spaceborne stellar interferometer that would be used to observe the stars.

Posted in: Briefs, TSP

Read More >>

Photodiode-Based, Passive Ultraviolet Dosimeters

Outputs of photodiodes are fed to coulometers.Simple, passive instruments have been developed for measuring the exposure of material specimens to vacuum ultraviolet (VUV) radiation from the Sun. Each instrument contains a silicon photodiode and a coulometer. The photocharge generated in the photodiode is stored in the coulometer. The accumulated electric charge measured by use of the coulometer is assumed to be proportional to the cumulative dose of VUV radiation expressed in such convenient units as equivalent Sun hours (ESH) [defined as the number of hours of exposure to sunlight at normal incidence]. Intended originally for use aboard spacecraft, these instruments could also be adapted to such terrestrial uses as monitoring the curing of ultraviolet-curable epoxies.

Posted in: Briefs

Read More >>

Measuring Radiation Patterns of Reconfigurable Patch Antennas on Wafers

Tests can be performed relatively inexpensively and without sawing wafers.An apparatus and technique have been devised for measuring the radiation pattern of a microwave patch antenna that is one of a number of identical units that have been fabricated in a planar array on a high-resistivity silicon wafer. The apparatus and technique are intended, more specifically, for application to such an antenna that includes a DC-controlled microelectromechanical system (MEMS) actuator for switching the antenna between two polarization states or between two resonance frequencies.

Posted in: Briefs

Read More >>

Hydraulic Apparatus for Mechanical Testing of Nuts

Advantages include mobility and reduced setup time.The figure depicts an apparatus for mechanical testing of nuts In the original application for which the apparatus was developed, the nuts are of a frangible type designed for use with pyrotechnic devices in spacecraft applications in which there are requirements for rapid, one-time separations of structures that are bolted together. The apparatus can also be used to test non-frangible nuts engaged without pyrotechnic devices.

Posted in: Briefs

Read More >>

The U.S. Government does not endorse any commercial product, process, or activity identified on this web site.