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Results for “Reflectometry”

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 91 records · Page 5
All sourcesNASA NTRSDOE OSTI
DOE OSTI2024

Apparatuses and methods for optical code-delay reflectometry (OcoDR)

Apparatuses and methods for optical code-delay reflectometry (OCoDR) are disclosed. An apparatus includes a modulator, a receiver, and control circuitry. The modulator is configured to receive incident electromagnetic (EM) radiation at a substantially fixed frequency generated by one or more EM radiation sources. The incident EM radiation includes continuous-wave EM radiation. The modulator is configured to impart a sequence onto an amplitude, a phase, or both of the incident EM radiation to generate modulated EM radiation. The modulated EM radiation includes continuous-wave EM radiation. The receiver is configured to receive reference EM radiation. The receiver is also configured to receive reflected EM radiation from an optical system responsive to the modulated EM radiation and generate interfered EM radiation responsive to the reference EM radiation and the reflected EM radiation. The receiver is further configured to generate a continuous interferogram responsive to the interfered EM radiation.

Seeley, Ryan↗
DOE OSTI2023

Cinematic reflectometry using QIKR, the quite intense kinetics reflectometer

The Quite Intense Kinetics Reflectometer (QIKR) will be a general-purpose, horizontal-sample-surface neutron reflectometer. Reflectometers measure the proportion of an incident probe beam reflected from a surface as a function of wavevector (momentum) transfer to infer the distribution and composition of matter near an interface. The unique scattering properties of neutrons make this technique especially useful in the study of soft matter, biomaterials, and materials used in energy storage. Exploiting the increased brilliance of the Spallation Neutron Source Second Target Station, QIKR will collect specular and off-specular reflectivity data faster than the best existing such machines. It will often be possible to collect complete specular reflectivity curves using a single instrument setting, enabling “cinematic” operation, wherein the user turns on the instrument and “films” the sample. Samples in time-dependent environments (e.g., temperature, electrochemical, or undergoing chemical alteration) will be observed in real time, in favorable cases with frame rates as fast as 1 Hz. Cinematic data acquisition promises to make time-dependent measurements routine, with time resolution specified during post-experiment data analysis. This capability will be deployed to observe such processes as in situ polymer diffusion, battery electrode charge–discharge cycles, hysteresis loops, and membrane protein insertion into lipid layers.

47 OTHER INSTRUMENTATION↗
DOE OSTI2022

Effect of Semiconducting Layer on Cable Insulation Damage Detection Using Surface Wave Reflectometry

This paper presents a study of the effect of the semiconducting layer present in medium and high voltage cables on surface wave propagation and its feasibility in detecting insulation damage on cables. Simulation studies were conducted using Ansys High Frequency Structure Simulator (HFSS). It was observed that attenuation increased with thicker semiconducting layer and higher conductivity of the layer. For instance, on a 24.4 mm diameter power cable, the electric field strength associated with a 1 GHz surface wave declines with distance and fades away after 30 m when a 2 mm thick semiconducting layer is present. More results as a function of semiconducting layer thickness, material conductivity and permittivity, distance of a damaged section, etc. will be presented.

reflectometry, unshielded power cable, semiconduct↗
DOE OSTI2021

High resolution density pedestal measurements during edge localized modes by short-pulse reflectometry in the TCV tokamak

Here, this publication presents high spatio-temporal resolution (mm µs -1 ) density profile measurements of the pedestal top during type I, III, and small edge localized mode (ELM) H-mode plasmas in the tokamak à configuration variable (TCV). These measurements were performed using a novel short-pulse reflectometer. Average inter-ELM density profiles are obtained via conditional averaging using the D α trace as ELM indicator. Changes to the pedestal density profile gradients prior to type-III ELMs reveal unique pedestal dynamics leading to the ELM crash which can provide important experimental data for validation of non-linear MHD ELM simulations. The small-ELM scenario is found to feature a ~25–35 kHz quasi-coherent density fluctuation near the separatrix ρ ψ 0.993–1.05 not observed during a similar type-I ELM discharge. This oscillation is also found in low-field-side magnetic pick-up probes displaying a ballooning character and n = +1 toroidal mode number. This oscillation could help explain the markedly different pedestal dynamics observed in the small-ELM regime.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2022

Miniature Crack or Damage Detection on Cable Insulation and Jacket Using Conformal Surface Wave Reflectometry

This letter introduces the study and application of a conformal surface wave launcher array to detect miniature insulation and/or jacket damage on unshielded cables. Here simulation and experimental results are presented that demonstrate that with the proposed concept very small instances of damage at various distances along power cables can be detected. Effects of damage detection feasibility in the presence of other cables in proximity and for cables containing semiconducting screen are also presented.

42 ENGINEERING↗
NASA NTRS2023

Basic Theory and Operating Principles of Optical Frequency Domain Reflectometry Measurement Systems as Applied to Fiber Bragg Grating Sensors

Optical frequency domain reflectometer (OFDR) systems provide for the interrogation of hundreds of fiber Bragg gratings (FBGs) within a single optical fiber. The coupling of FBG sensors to an OFDR interrogator results in a highly distributed measurement system utilizing sensors that are lightweight, immune to electromagnetic interference, and low-profile. This paper presents and explores a basic derivation of OFDR-FBG signals, the processing of those signals, the assembly of a basic OFDR system, an example measurement scenario, and the effects of specific component and configuration changes on interrogator speed, resolution, and accuracy.

optical frequency domain reflectometry↗
DOE OSTI2026

Neutron Reflectometry Reveals Diffusion in Contrast-Matched Brush Particle Bilayers

A material system for performing layer-spread experiments on brush particle bilayers is presented and used to determine the diffusion constant of brush particles in the melt state. Selective deuteration of the core and shell of organo-silica nanoparticles grafted with poly(methyl methacrylate) was used to match the scattering length density of the core and the polymer canopy layer. This subdued the scattering of particle cores (i.e., formfactor scattering) and enabled the analysis of the interdiffusion kinetics using neutron reflectivity. For low molecular grafts, i.e., grafts with a molecular weight below the entanglement limit, the interdiffusion kinetics revealed both a sub- and Fickian diffusion regime. The former was attributed to the local dynamics that was constrained by the slow-moving cores of neighboring brush particles that acted as long-lived physical cross-links. No transition to Fickian diffusion was observed for entangled systems, even at prolonged annealing times. This suggested a higher level of kinetic restraint in entangled brush particle melts as compared to, for example, star polymers with a comparable chain length for which Fickian diffusion has been reported under similar conditions.

Diffusion, Polymer Grafted Nanoparticles, Neutron ↗