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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 235 records · Page 13
All sourcesNASA NTRSDOE OSTI
NASA NTRS2021

Simultaneous Focused Laser Differential Interferometry and High-Speed Schlieren in a Mach 6 Flow

An instrument is demonstrated that is capable of simultaneous and independent flow density fluctuation measurements over the same line-of-sight by combining two optical techniques: focused laser differential interferometry (FLDI) and high-speed schlieren (HSS). The FLDI instrument measures fluctuations at a single point in the flowfield at 10 MHz, with the resulting signal most sensitive in the region nearest the focal plane of the FLDI laser beam. The HSS instrument acquires images at 20 kHz along the same optical axis as the FLDI beam, but with the resulting signal path averaged over the entire HSS line-of-sight. The introduction of the HSS optics into the FLDI beam path provides two high-quality measurement capabilities in a single system with no degradation of performance relative to stand-alone FLDI or HSS instruments.

Focused Laser Differential Interferometry↗
NASA NTRS2021

Angle Dependence of Focused X-Ray-Induced Single Event Transients in an Epitaxial Silicon Diode

Focused X-Ray single event transient (SET) experiments are performed at small angles on an epitaxial silicon diode at two reverse bias conditions. For both biases, the collected charge and peak current results follow the cosine law, while the transient fall time remains independent of incident angle. This demonstrates that only the amount of charge being generated is affected by angle and not the fundamental device response.

Heavy ions↗
NASA NTRS2022

Angle Dependence of Focused X-Ray-Induced Single Event Transients in an Epitaxial Silicon Diode

Focused X-Ray single event transient (SET) experiments are performed at small angles on an epitaxial silicon diode at two reverse bias conditions. For both biases, the collected charge and peak current results follow the cosine law, while the transient fall time remains independent of incident angle. This demonstrates that only the amount of charge being generated is affected by angle and not the fundamental device response for these relatively large devices.

Focused X-ray↗
NASA NTRSDate not supplied

High-Speed Self-Aligned Focusing Schlieren and Background-Oriented Schlieren with Pulsed Laser Illumination

Laser light sources are commonly used in schlieren-based flow visualization techniques that are in development at NASA Langley Research Center. Of particular interest are high-intensity, low coherence sources that allow for high signal-to-noise schlieren imagery to be acquired without the laser speckle that typically occurs as a result of interference. Results from a self-aligned focusing schlieren system developed at NASA Langley and a background-oriented schlieren system are presented to highlight the effectiveness of these sources.

Schlieren↗
NASA NTRSDate not supplied

Recent Progress and Development of Self-Aligned Focusing Schlieren

A broad range of developments and applications of self-aligned focusing schlieren (SAFS)systems is presented. The replacement of the Ronchi ruling (RR) with a𝜇LCD was demonstrated with digital SAFS, which provides the ability to modulate the pattern and orientation without physical intervention. Additionally, replacement of the traditional RR with spectral-spatial filters was demonstrated to yield the ability to simultaneously image horizontal and vertical index of refraction gradients using two separate wavelengths. The application of the Scheimpflug principle to SAFS systems enables off-axis imaging and allowed for extended fields-of-view to be captured using a two-camera system. The addition of a plenoptic camera to a baseline SAFS system enables refocusing capabilities, which is demonstrated on two jets offset along the optical axis. Furthermore, application of an event-based camera to SAFS was shown to enable acquisition of sparse, spatio-temporal data. Beyond the listed developments, SAFS was applied to difficult and constraining facilities, such as the National Full-Scale Aerodynamics Complex(NFAC) 80- by 120-ft Wind Tunnel and the Thermal Acoustic Engines (TAE) rig at NASA Ames Research Center and NASA Glenn Research Center, respectively. Behavior of Ronchi rulings, Rochon prisms, and the use of quarter-wave plates versus quarter-wave films are evaluated to provide insight for future experimental design of SAFS-systems.

Self-Aligned Focusing Schlieren↗