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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 667 records · Page 37
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Enhanced spatial resolution of Eljen-204 plastic scintillators for use in rep-rated proton diagnostics

A pixelated scintillator has been designed, fabricated, and tested using a laser-accelerated proton source for use in proton diagnostics at rep-rated laser facilities. The work presented here demonstrates the enhanced spatial resolution of thin, organic scintillators through a novel pixelation technique. Furthermore, experimental measurements using laser-generated protons incident onto 130 μm-thick scintillators indicate a >20% reduction in the scintillator point spread function (PSF) for the detectors tested. The best performing pixelated detector reduced the ~200 μm PSF of the stock material to ~150 μm. The fabrication technique may be tailored to reduce the pixel size and achieve higher spatial resolutions.

47 OTHER INSTRUMENTATION↗
NASA NTRS2015

Qualification of a Multi-Channel Infrared Laser Absorption Spectrometer for Monitoring CO, HCl, HCN, HF, and CO2 Aboard Manned Spacecraft

Monitoring of specific combustion products can provide early-warning detection of accidental fires aboard manned spacecraft and also identify the source and severity of combustion events. Furthermore, quantitative in situ measurements are important for gauging levels of exposure to hazardous gases, particularly on long-duration missions where analysis of returned samples becomes impractical. Absorption spectroscopy using tunable laser sources in the 2 to 5 micrometer wavelength range enables accurate, unambiguous detection of CO, HCl, HCN, HF, and CO2, which are produced in varying amounts through the heating of electrical components and packaging materials commonly used aboard spacecraft. Here, we report on calibration and testing of a five-channel laser absorption spectrometer designed to accurately monitor ambient gas-phase concentrations of these five compounds, with low-level detection limits based on the Spacecraft Maximum Allowable Concentrations. The instrument employs a two-pass absorption cell with a total optical pathlength of 50 cm and a dedicated infrared semiconductor laser source for each target gas. We present results from testing the five-channel sensor in the presence of trace concentrations of the target compounds that were introduced using both gas sources and oxidative pyrolysis (non-flaming combustion) of solid material mixtures.

environmental monitoring↗
DOE OSTI2020

Bayesian Optimization of a Free-Electron Laser

The Linac Coherent Light Source X-ray free-electron laser is a complex scienti c apparatus which changes con gurations multiple times per day, necessitating fast tuning strategies to reduce setup time for successive experiments. To this end, we employ a Bayesian approach to maximizing X- ray laser pulse energy by controlling groups of quadrupole magnets. A Gaussian process model provides probabilistic predictions for the machine response with respect to control parameters, enabling a balance of exploration and exploitation in the search for the global optimum. We show that the model parameters can be learned from archived scans, and correlations between devices can be extracted from the beam transport. Furthermore, the result is a sample-e cient optimization routine, combining both historical data and knowledge of accelerator physics to signi cantly outperform existing optimizers.

47 OTHER INSTRUMENTATION↗
NASA NTRS1975

Heterodyne spectroscopy of astronomical and laboratory sources at 8.5 microns using diode laser local oscillators

The first 8.5 microns infrared heterodyne spectrometer has been constructed using tuneable semiconductor (PbSe) diode lasers and was used to measure absorption line profiles of N2O in the laboratory, as well as black-body emission from the moon and from Mars. Spectral information was recorded over a 200 MHz bandwidth using an 8-channel filter bank. The resolution was 25 MHz (6 millionths of a micron), and the minimum detectable (black-body) power was approximately 1 times 10 to the minus 16th power W for 8 min of integration. The results demonstrate the usefulness of heterodyne spectroscopy for the study of remote and local sources in the infrared.

Mumma, M.↗
NASA NTRS1994

Laser action in far-infrared astrophysical sources

Employing new atomic data and a 15 level collisional-radiative model, it is shown that population inversion, and consequent laser action, can be achieved in far-infrared (FIR) lines (C II) 157 micrometer, (N III) 58 micrometer, (O IV) 26 micrometer, (Ne VI) 7.6 micrometer, and (Mg VIII) 3 micrometer. Coupling of the lasting transition 2s(sup 2)2p((sup 2)P(sup o sub 3/2)-(sup 2)P(sup o sub 1/2)) to higher energy levels of the 2s2p(sup 2) configuration in boron-like ions provides the dominant pumping flux. Lasing column lengths are found to be l approximately equal 10(exp -4)-1.0 pcs, at T(sub e) approximately equal 10(exp 4)-10(exp 6) K, N(sub e) approximately equal 10(exp 4)-10(exp 10)/cu cm, conditions and sizes prevalent in broad-line regions of active-galactic nuclei and novae. Detectable emission fluxes are estimated. Lasing activity in the source could significantly affect abundance determinations. The FIR line emission should be readily observable with the upcoming Infrared Space Observatory.

Peng, Jianfang↗
NASA NTRS1972

Laser induced fluorescence in algae: A new technique for remote detection

Measurements of the absorption and fluorescence spectra were obtained for four various types of marine and fresh water algae using a pulsed N2/Ne dye laser as the source of excitation. The absorption maxima for the algae ranged from 420 to 675 nm, while their fluorescent spectra ranged from 580 to 685 nm. It appears feasible that various algal species can be identified by detection of their fluorescent signatures using a tunable laser as the excitation source. However, if one is concerned only with detection of chlorophyll a, the optimum excitation is approximately 600 + 50 nm while detection is at 685 nm. An analysis of both calculations and laboratory results indicates that it should be feasible to measure chlorophyll a in concentrations as low as 1.0 mg/m3 using a 100 kW peak pulsed laser from an altitude of 500 meters.

Friedman, E. J.↗
NASA NTRS1991

Laser discrimination by stimulated emission of a phosphor

A method for discriminating sources of UV, near infrared, and far infrared laser radiation was discovered. This technology is based on the use of a single magnesium sulfide phosphor doubly doped with rare earth ions, which is thermally/optically stimulated to generate colors correlatable to the incident laser radiation. The phosphor, after initial charging by visible light, exhibits green stimulated luminescence when exposed to a near infrared source (Nd: YAG laser). On exposure to far infrared sources (CO2 laser) the phosphor emission changes to orange color. A UV laser produces both an orange red as well as green color. A device using this phosphor is useful for detecting the laser and for discriminating between the near infrared, far infrared, and UV lasers. The technology is also capable of infrared laser diode beam profiling since the radiation source leaves an imprint on the phosphor that can be photographed. Continued development of the technology offers potential for discrimination between even smaller bandwidths within the infrared spectrum, a possible aid to communication or wavemixing devices that need to rapidly identify and process optical signals.

Mathur, V. K.↗
DOE OSTI2021

Compact, portable, laser induced fluorescence diagnostic for laboratory plasma sources

As diagnostic groups are increasingly called upon to participate in experimental campaigns at remote facilities, there is a need to develop portable versions of plasma diagnostic systems. One such diagnostic is laser induced fluorescence (LIF). Here, we describe a portable LIF apparatus that eliminates the need for an optical table, beam splitters, and an optical chopper. All of the light exiting the laser system is coupled through optical fibers to the experiment and housekeeping diagnostics. Here, the collected light is coupled through an optical fiber as well. A key feature is modulation of the tapered amplifier current instead of physical modulation of the laser output. Using this portable LIF system, measurements of ion temperature, ion flow, and relative metastable ion density are reported for two different remote experiments.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2026

Phase-controlled direct laser acceleration enabled by longitudinal variation of the laser-driven quasi-static plasma magnetic field

Direct laser acceleration (DLA) enables energy transfer from an ultra-high-intensity laser to plasma electrons and underpins many laser-driven particle and radiation-source concepts. A laser-driven azimuthal plasma magnetic field is a key player in this process: it confines energetic electrons, induces betatron oscillations, and makes possible a resonant interaction between the betatron motion and the laser field. While this betatron resonance can enhance electron energy gain, the gain itself generally drives frequency detuning and promotes largely reversible energy exchange that limits net acceleration. Here we show, using a test-electron model with prescribed fields, that a slow longitudinal increase of the quasi-static plasma magnetic field qualitatively changes DLA by introducing hysteresis in the ratio of the betatron frequency to the laser frequency experienced by the electron, so that this ratio depends on the prior evolution of the electron even at the same energy. This hysteresis enables phase control of the electron-laser energy exchange and suppresses the usual reversibility of DLA, allowing electrons to retain the acquired energy and sustain energy gain without intermittent losses.

direct laser acceleration↗
DOE OSTI2024

A Path to 100 Percent Renewable Energy: Grid-Forming Inverters will Give Us the Grid We Need Now

This is a more urgent problem than it might sound. The westernmost Hawaiian island of significant size, Kauai is home to around 70,000 residents and 30,000 tourists at any given time. Renewable energy accounts for 70 percent of the energy produced in a typical year - a proportion that's among the highest in the world and that can be hard to sustain for such a small and isolated grid. During the day, the local system operator, the Kauai Island Utility Cooperative, sometimes reaches levels of 90 percent from solar alone. But on 2 April, the 26-MW generator was running near its peak output, to compensate for the drop in solar output as the sun set. At the moment when it failed, that single generator had been supplying 60 percent of the load for the entire island, with the rest being met by a mix of smaller generators and several utility-scale solar-and-battery systems.

battery management systems↗
DOE OSTI2021

NNSA Light Source Enhancements: Coupling a High Energy Laser Driver to an XFEL

NNSA has an unmet capability gap to predict how changes in material microstructure, due to aging and new manufacturing practices, can affect performance at extremes. This capability gap is the basis for the Dynamic Mesoscale Material Science Capability (DMMSC) CD-0 that was signed in 2015 [1]. Because of the delay to the MaRIE facility approach, the Tri-Lab in March 2020 proposed separate complementary investments at the APS and LCLS to address portions of the DMMSC mission need [2].

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
NASA NTRS1978

Apparatus for extraction and separation of a preferentially photo-dissociated molecular isotope into positive and negative ions by means of an electric field

Molecules of one and the same isotope were preferentially photodissociated by a laser and an ultraviolet source, or by multiphoton absorption of laser radiation. The resultant ions were confined with a magnetic field, moved in opposite directions by an electric field, extracted from the photodissociation region by means of screening and accelerating grids, and collected in ducts.

Wilhelm, H. E.↗
NASA NTRS1986

Two-photon laser-induced fluorescence detection of OH

The TP-LIF OH sensor is based on the principle that a molecule having multiple energy states, all of which are bonding, can be pumped into the highest state with the resulting fluorescence being blue-shifted relative to all pumping wavelengths. In this way, one can successfully discriminate against virtually all noise sources in the system using long wavelength blocking filters in conjunction with solar-blind photomultiplier tubes. Thus, these systems tend to be signal limited rather than signal-to-noise limited as is true of the SP-LIF technique as well as other conventional analytical methods. The trick to achieving the above sampling scheme, with high efficiency, is in the use of high photon fluxes of short time duration. Obviously, the latter type of light source is fulfilled nicely by available pulsed lasers. From an operational point of view, however, this laser source needs to be tunable. The latter characteristic permits extremely high selectivity for the detection of a diatomic or simple polyatomic molecule by taking advantage of the high-resolution spectroscopic features of these type species.

Davis, D. D.↗
NASA NTRS2011

Optimized Biasing of Pump Laser Diodes in a Highly Reliable Metrology Source for Long-Duration Space Missions

Optical metrology system reliability during a prolonged space mission is often limited by the reliability of pump laser diodes. We developed a metrology laser pump module architecture that meets NASA SIM Lite instrument optical power and reliability requirements by combining the outputs of multiple single-mode pump diodes in a low-loss, high port count fiber coupler. We describe Monte-Carlo simulations used to calculate the reliability of the laser pump module and introduce a combined laser farm aging parameter that serves as a load-sharing optimization metric. Employing these tools, we select pump module architecture, operating conditions, biasing approach and perform parameter sensitivity studies to investigate the robustness of the obtained solution.

808 mm diode pumps↗