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Results for “Optical physics”

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 973 records · Page 54
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Characterization of an imploding cylindrical plasma for electron transport studies using x-ray emission spectroscopy

We report here on the characterization of the conditions of an imploding cylindrical plasma by time-resolved x-ray emission spectroscopy. Knowledge about this implosion platform can be applied to studies of particle transport for inertial confinement fusion schemes or to astrophysical plasmas. A cylindrical Cl-doped CH foam within a tube of solid CH was irradiated by 36 beams (I total ~5×10 14 W/cm 2 , 1.5ns square pulse, and E total ~ 16.2kJ) of the OMEGA-60 laser to radially compress the CH toward the axis. The analysis of the time-resolved spectra showed that the compression can be described by four distinct phases, each presenting different plasma conditions. First the ablation of the cylinder is dominant; second, the foam is heated and induces a significant jump in emission intensities; third, the temperature and density of the foam reaches a maximum; and finally, the plasma expands. Ranges for the plasma temperature were inferred with the atomic physics code SCRAM (Spectroscopic Collisional-Radiative Atomic Model) and the experimental data have been compared to hydrodynamic simulations performed with the 2D code FLASH, which showed a similar implosion dynamic over time.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2021

Simulations of wavelength-multiplexed holography for single-shot spatiotemporal characterization of NIF’s advanced radiographic capability (ARC) laser

We simulate the use of a newly developed single-shot wavelength-multiplexed holography-based diagnostic, STRIPED FISH, to fully characterize the as-delivered laser pulses of the National Ignition Facility’s Advanced Radiographic Capability (NIF-ARC) laser. To that end, we have performed simulations of the NIF-ARC pulse incorporating (a) a time-integrated spatial-profile measurement and a complete temporal-intensity-and-phase measurement using a frequency resolved optical gating, but without any spatiotemporal pulse characterizations, and (b) simulated first-order spatiotemporal distortions, which could be measured on a single shot if a STRIPED FISH device were deployed.

47 OTHER INSTRUMENTATION↗
DOE OSTI2023

A novel approach to interface high-Q Fabry–Pérot resonators with photonic circuits

The unique benefits of Fabry–Pérot resonators as frequency-stable reference cavities and as an efficient interface between atoms and photons make them an indispensable resource for emerging photonic technologies. To bring these performance benefits to next-generation communications, computation, and time-keeping systems, it will be necessary to develop strategies to integrate compact Fabry–Pérot resonators with photonic integrated circuits. In this paper, we demonstrate a novel reflection cancellation circuit that utilizes a numerically optimized multi-port polarization-splitting grating coupler to efficiently interface high-finesse Fabry–Pérot resonators with a silicon photonic circuit. This circuit interface produces a spatial separation of the incident and reflected waves, as required for on-chip Pound–Drever–Hall frequency locking, while also suppressing unwanted back reflections from the Fabry–Pérot resonator. Using inverse design principles, we design and fabricate a polarization-splitting grating coupler that achieves 55% coupling efficiency. This design realizes an insertion loss of 5.8 dB for the circuit interface and more than 9 dB of back reflection suppression, and we demonstrate the versatility of this system by using it to interface several reflective off-chip devices.

Optics↗
DOE OSTI2026

Advanced monolithic 2D multilayer Laue lens (MLL) optics for hard x-ray nanofocusing and nanotomography

We report on the development of a new generation of monolithic two-dimensional (2D) multilayer Laue lens (MLL) optics suitable for high-resolution hard x-ray nanoimaging. The 2D optics were assembled on microfabricated silicon templates with high orthogonality and lateral alignment precision, which were characterized using white-light interferometry and confirmed by x-ray measurements. The developed monolithic 2D MLL optics were successfully employed for hard x-ray nanofocusing and nanotomography experiments using the ptychography imaging modality, demonstrating sub-10 nm resolution in 2D and sample-limited ∼30 nm in three-dimensional while exhibiting excellent stability during extended measurements. The new 2D MLL templates with high alignment accuracy represent an important step forward in the development of 2D MLL optics toward direct nanoimaging experiments with sub-10 nm spatial resolution.

36 MATERIALS SCIENCE↗
DOE OSTI2017

Holographic mode wavefront sensor with an enlarged number of measured modes

A holographic mode wavefront sensor is proposed, which makes it possible to measure up to several tens of wavefront modes. The increase in the number of measured modes is implemented using the conversion of a light wave entering the sensor into a wide diffuse light beam, which allows one to record a large number of holograms, each intended for measuring one of the modes. (holographic sensors)

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2016

Quantification of online removal of refractory black carbon using laser-induced incandescence in the single particle soot photometer

Refractory black carbon (rBC) is an aerosol that has important impacts on climate and human health. rBC is often mixed with other species, making it difficult to isolate and quantify its important effects on physical and optical properties of ambient aerosol. To solve this measurement challenge, a new method to remove rBC was developed using laser-induced incandescence (LII) by Levin et al. in 2014. Application of the method with the Single Particle Soot Photometer (SP2) is used to determine the effects of rBC on ice nucleating particles (INP). Here, we quantify the efficacy of the method in the laboratory using the rBC surrogate Aquadag. Polydisperse and mobility-selected samples (100–500 nm diameter, 0.44–36.05 fg), are quantified by a second SP2. Removal rates are reported by mass and number. For the mobility-selected samples, the average percentages removed by mass and number of the original size are 88.9 ± 18.6% and 87.3 ± 21.9%, respectively. Removal of Aquadag is efficient for particles >100 nm mass-equivalent diameter (d me ), enabling application for microphysical studies. However, the removal of particles ≤100 nm d me is less efficient. Absorption and scattering measurements are reported to assess its use to isolate brown carbon (BrC) absorption. Scattering removal rates for the mobility-selected samples are >90% on average, yet absorption rates are 53% on average across all wavelengths. Therefore, application to isolate effects of microphysical properties determined by larger sizes is promising, but will be challenging for optical properties. Lastly, the results reported also have implications for other instruments employing internal LII, e.g., the Soot Particle Aerosol Mass Spectrometer (SP-AMS).

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2014

Electron-impact ionization of the N atom

Electron-impact ionization cross sections for the ground and excited states of the N atom are calculated using the non-perturbative R-matrix with pseudo-states and time-dependent close-coupling (TDCC) methods, as well as the perturbative distorted-wave method. The TDCC and distorted-wave results for the $1{{{\rm s}}^{2}}2{{{\rm s}}^{2}}2{{{\rm p}}^{2}}3l$ ($l=0-2$) excited configurations are much larger than for the ground configuration. In all cases the TDCC results are substantially lower than the distorted-wave results. The ionization cross section results will lead to a better understanding of moderately dense astrophysical and laboratory plasmas containing nitrogen.

Optics↗
DOE OSTI2017

Electron-impact single and double ionization of the Mn 2+ , Mn 3+ and Mn 4+ atomic ions

Electron-impact single and double ionization cross sections for Mn2+, Mn3+ and Mn4+ are calculated using a semi-relativistic configuration-average distorted-wave method. The ionization cross sections include contributions from single direct ionization, double direct ionization and excitation–autoionization. Certain excitations may contribute to both single and double ionization as determined by branching ratio calculations. For Mn2+ the ratio of the double to single ionization cross section peak heights is found to be 0.15, while dropping to 0.03 for Mn3+ and 0.01 for Mn3+.

Optics↗
DOE OSTI2017

Electron-impact single and double ionization of W

Electron-impact single and double ionization cross sections for the W atom are calculated using a semi-relativistic distorted-wave method. The cross sections include contributions from single direct ionization, double direct ionization and excitation-autoionization. Branching ratio calculations are made to determine whether an excitation may contribute to single or double ionization. We check the accuracy of the semi-relativistic distorted-wave calculations for direct ionization of various subshells by comparison with fully-relativistic distorted-wave calculations. We also check the accuracy of the perturbative distorted-wave calculations for direct ionization of the outer most subshells by comparison with non-perturbative time-dependent close-coupling calculations.

Optics↗
DOE OSTI2017

H - photodetachment and radiative attachment for astrophysical applications

We combine R-matrix calculations, asymptotic relations, and comparison to available experimental data to construct an H- photodetachment cross section reliable over a large range of photon energies and take into account the series of auto-detaching shape and Feshbach resonances between 10.92 and 14.35 eV. The accuracy of the cross section is controlled by ensuring that it satisfies all known oscillator strength sum rules, including contributions from the resonances and single-photon double-electron photodetachment. From the resulting recommended cross section, spontaneous and stimulated radiative attachment rate coefficients are obtained. Photodetachment rates are also computed for the standard interstellar radiation field, in diffuse and dense interstellar clouds, for blackbody radiation, and for high redshift distortion photons in the recombination epoch. Implications are investigated for these astrophysical radiation fields and epochs.

Optics↗