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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 595 records · Page 33
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Hot-electron generation at direct-drive ignition-relevant plasma conditions at the National Ignition Facility

Laser–plasma interaction instabilities can be detrimental for direct-drive inertial confinement fusion by generating high-energy electrons that preheat the target. Moreover, an experimental platform has been developed and fielded on the National Ignition Facility to investigate hot-electron production from laser–plasma instabilities at direct-drive ignition-relevant conditions. The radiation-hydrodynamic code DRACO has been used to design planar-target experiments that generate plasma and interaction conditions comparable to direct-drive ignition designs: I L ~10 15 W/cm 2 , T e > 3 keV, and density-gradient scale lengths of L n ~ 600 μ m in the quarter-critical density region. The hot-electron properties were inferred by comparing the experimentally observed hard x-ray spectra to Monte Carlo simulations of hard x-ray emission from hot electrons depositing energy in the target. Hot-electron temperatures of ~40 keV to 60 keV and the fraction of laser energy converted to hot electrons of ~0.5% to 5% were inferred in plastic targets for laser intensities at the quarter-critical density surface of (~4 to 14) × 10 14 W/cm 2 . The use of silicon ablators was found to mitigate the hot-electron preheat by increasing the threshold laser intensity for hot-electron generation from ~3.5 × 10 14 W/cm 2 in plastic to ~6 × 10 14 W/cm 2 in silicon. The overall hot-electron production is further reduced in silicon ablators when the intensity threshold is exceeded.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
NASA NTRS1984

Laser Docking System

The Laser Docking System (LDS) consists of passive docking aids (reflectors) placed on the target vehicle in a known location and orientation. These reflectors are acquired and tracked by means of a modulated laser beam located on the interceptor vehicle. The LDS enables the interceptor vehicle to analyze the return (reflected) signal in order to determine both relative position and relative attitude of the target vehicle during stationkeeping and docking. Laser ranging experiments have been accomplished at NASA, and from these experiments have evolved laser docking concepts. The concepts include angle and attitude measurement which are capable of providing all of the information needed for automatic docking control by the interceptor vehicle. Several designs are being compared. Plans include the development and testing of: first a breadboard model, then an engineering model, and finally qualification and flight systems.

Erwin, H. O.↗
NASA NTRS2010

Swept Frequency Laser Metrology System

A swept frequency laser ranging system having sub-micron accuracy that employs multiple common-path heterodyne interferometers, one coupled to a calibrated delay-line for use as an absolute reference for the ranging system. An exemplary embodiment uses two laser heterodyne interferometers to create two laser beams at two different frequencies to measure distance and motions of target(s). Heterodyne fringes generated from reflections off a reference fiducial X(sub R) and measurement (or target) fiducial X(sub M) are reflected back and are then detected by photodiodes. The measured phase changes Delta phi(sub R) and Delta phi (sub m) resulting from the laser frequency swept gives target position. The reference delay-line is the only absolute reference needed in the metrology system and this provides an ultra-stable reference and simple/economical system.

Zhao, Feng↗
DOE OSTI2021

Preshot Report for the NIF DDCyl Campaign: H_Hyd_DDCyl_DRT_AAA/BBB/CCC

The first two cylinder shot days on the National Ignition Facility, allocated through the Discovery Science program, provided a successful demonstration of the cylinder platform on the NIF. Both of these shot days used cylinders that were nominally 3 times larger in radial dimension than cylinders fielded at the OMEGA laser facility, here referred to as scale-3 targets. In the first Discovery Science shot day, we demonstrated that Rayleigh-Taylor instability growth during the deceleration phase is scale-invariant between the scale-1 OMEGA experiments and similarly tailored scale-3 NIF experiments at the same convergence ratio of CR=initial radius/final radius=2.25. In the second Discovery Science shot day, we increased the convergence ratio by lowering the density of the central foam from 300 mg/cm 3 to roughly 40 mg/cm 3 with the same laser drive, resulting in a higher CR=5 at the time when the rebounding shock strikes the aluminum marker. We also greatly improved the imaging setup for the second shot day, resulting in much higher quality (greater signal-to-noise) radiographs of the implosion. This current shot day was awarded through the High Energy Density (HED) Council, following this demonstration of platform viability. It was originally scheduled for June 2020, but it was postponed several times due to the COVID-19 pandemic. It is currently scheduled for January 6, 2021. For this shot day, we will increase the radial dimension of the cylinder to four times the OMEGA-scale targets, and these will be referred to as scale-4 cylinders. Increasing the radial dimension of the target is advantageous as we push these targets to higher convergence ratio. By starting with an initially larger target, the target can push to a higher CR while maintaining the same final viewing area. Other than the larger radial dimension, the targets are very similar in design to the previous ones, consisting of an epoxy ablator, an embedded aluminum marker layer, and a low density central CH foam. These will also use a 40 mg/cm3 CH foam, reaching a CR~4.5 with the same laser energy (the added target mass reduces the final CR slightly). Note that this is NOT designed to be scale-invariant with the previous scale-1 OMEGA and scale-3 NIF shots. It was determined that the laser energy required to achieve a scale-invariant implosion was above the allowable optics damage limits (though achievable on the NIF) for these scale-4 targets.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
NASA NTRS1977

NASA ground-based and space-based laser ranging systems

The development of NASA laser ranging systems is discussed with reference to applications such as orbit determination, gravity-field studies, and analyses of polar motion, earth tides, and tectonic plate motion. Several laser ranging designs are described noting the first satellite laser ranging experiment, the Moblas II and III systems, and the laser ranging satellites presently in orbit. Primary error sources are identified as atmospheric delay, optical signal-to-noise ratios, the electron multiplier, time-interval measurements, and target noise. Plans for Shuttle-based laser ranging systems are reviewed noting simulation studies of 12-day Shuttle missions.

Fitzmaurice, M. W.↗
DOE OSTI2026

Status and performance of the GlueX DIRC

In support of the future physics program at Ce+BAF, we propose a prototype positron target. The prototype target consists of a tungsten disk mounted on a water-cooled copper support structure to enhance heat removal. The primary goals of this work are to benchmark CFD simulations, ensure vacuum integrity at the 10^-6 Pa level, achieve stable target rotation up to 10 Hz, and implement efficient water-based cooling for sustained high-power operation. To manage the thermal load, the target is designed to rotate, allowing the deposited heat to spread over a larger region, and thereby reducing localized thermal stress while maintaining the maximum temperature below 1000 K. To experimentally evaluate the thermal performance and structural stability of the target, we plan to conduct high-power laser heating tests at Laser Lab 5, LERF Building, JLab. These tests will serve as a stepping-stone for the positron production target at CEBAF.

Stevens, J.R. [College of William and Mary, Willia↗
DOE OSTI2023

High-bandwidth image-based predictive laser stabilization via optimized Fourier filters

Controlling the delivery of kHz-class pulsed lasers is of interest in a variety of industrial and scientific applications, from next-generation laser-plasma acceleration to laser-based x-ray emission and high-precision manufacturing. The transverse position of the laser pulse train on the application target is often subject to fluctuations by external drivers (e.g., room cooling and heating systems, motorized optics stages and mounts, vacuum systems, chillers, and/or ground vibrations). For typical situations where the disturbance spectrum exhibits discrete peaks on top of a broad-bandwidth lower-frequency background, traditional PID (proportional-integral-derivative) controllers may struggle, since as a general rule PID controllers can be used to suppress vibrations up to only about 5%–10% of the sampling frequency. Here, a predictive feed-forward algorithm is presented that significantly enhances the stabilization bandwidth in such laser systems (up to the Nyquist limit at half the sampling frequency) by online identification and filtering of one or a few discrete frequencies using optimized Fourier filters. Furthermore, the system architecture demonstrated here uses off-the-shelf CMOS cameras and piezo-electric actuated mirrors connected to a standard PC to process the alignment images and implement the algorithm. To avoid high-end, high-cost components, a machine-learning-based model of the piezo mirror’s dynamics was integrated into the system, which enables high-precision positioning by compensating for hysteresis and other hardware-induced effects. A successful demonstration of the method was performed on a 1 kHz laser pulse train, where externally-induced vibrations of up to 400 Hz were attenuated by a factor of five, far exceeding what could be done with a standard PID scheme.

Natal, Joseph↗
NASA NTRS2014

Calcium Sulfate Characterized by Chemcam/Curiousity at Gale Crater, Mars

Onboard the Mars Science Laboratory (MSL) Curiosity rover, the ChemCam instrument consists of : (1) a Laser-Induced Breakdown Spectrometer (LIBS) for elemental analysis of the targets and (2) a Remote Micro Imager (RMI), for the imaging context of laser analysis. Within the Gale crater, Curiosity traveled from Bradbury Landing through the Rocknest region and into Yellowknife Bay (YB). In the latter, abundant light-toned fracture-fill material occur. ChemCam analysis demonstrates that those fracture fills consist of calcium sulfates.[

Nachon, M.↗
DOE OSTI2020

Effect of cross-beam energy transfer on target-offset asymmetry in direct-drive inertial confinement fusion implosions

The unintentional mispositioning of inertial confinement fusion (ICF) capsules from the center of laser beam convergence has long been shown in simulations to generate large ℓ = 1 asymmetry and significantly degrade implosion symmetry and fusion yields. Experimental yields on the OMEGA Laser System, however, have shown much less sensitivity to this initial target offset. This paper presents simulations of offset ICF implosions improved by including a physics model of cross-beam energy transfer (CBET), a mechanism of laser energy scattering from one beam to another. Room-temperature OMEGA implosion experiments with prescribed target offsets are simulated with and without CBET, illustrating that CBET mitigates the ℓ = 1 implosion asymmetry from target offset. Here, comparison of simulations to multiple complementary experimental observables indicates the addition of CBET physics in offset simulations is necessary to match experimental results.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2025

Generation of radioisotopes for medical applications using high-repetition, high-intensity lasers

We used the PW high-repetition laser facility VEGA-3 at Centro de Láseres Pulsados in Salamanca, with the goal of studying the generation of radioisotopes using laser-driven proton beams. Various types of targets have been irradiated, including in particular several targets containing boron to generate α-particles through the hydrogen–boron fusion reaction. We have successfully identified γ-ray lines from several radioisotopes created by irradiation using laser-generated α-particles or protons including 43 Sc, 44 Sc, 48 Sc, 7 Be, 11 C and 18 F. We show that radioisotope generation can be used as a diagnostic tool to evaluate α-particle generation in laser-driven proton–boron fusion experiments. We also show the production of 11 C radioisotopes, ≈ 6 × 10 6 , and of 44 Sc radioisotopes, ≈ 5 × 10 4 per laser shot. This result can open the way to develop laser-driven radiation sources of radioisotopes for medical applications.

gamma ray spectroscopy↗
NASA NTRS1986

He-Ne and CW CO2 laser long-path systems for gas detection

This paper describes the design and testing of a laboratory prototype dual He-Ne laser system for the detection of methane leaks from underground pipelines and solid-waste landfill sites using differential absorption of radiation backscattered from topographic targets. A laboratory-prototype dual CW carbon dioxide laser system also using topographic backscatter is discussed, and measurement results for methanol are given. With both systems, it was observed that the time-varying differential absorption signal was useful in indicating the presence of a gas coming from a nearby source. Limitations to measurement sensitivity, especially the role of speckle and atmospheric turbulence, are described. The speckle results for hard targets are contrasted with those from atmospheric aerosols. The appendix gives appropriate laser lines and values of absorption coefficients for the hydrazine fuel gases.

Grant, W. B.↗
DOE OSTI2021

Effect of cross-beam energy transfer on target-offset asymmetry in direct-drive inertial confinement fusion implosions

The unintentional mispositioning of inertial confinement fusion (ICF) capsules from the center of laser beam convergence has long been shown in simulations to generate large ℓ = 1 asymmetry and significantly degrade implosion symmetry and fusion yields. Experimental yields on the OMEGA Laser System, however, have shown much less sensitivity to this initial target offset. This paper presents simulations of offset ICF implosions improved by including a physics model of cross-beam energy transfer (CBET), a mechanism of laser energy scattering from one beam to another. Room-temperature OMEGA implosion experiments with prescribed target offsets are simulated with and without CBET, illustrating that CBET mitigates the ℓ = 1 implosion asymmetry from target offset. Comparison of simulations to multiple complementary experimental observables indicates the addition of CBET physics in offset simulations is necessary to match experimental results.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
NASA NTRS1995

Receiver design, performance analysis, and evaluation for space-borne laser altimeters and space-to-space laser ranging systems

Laser altimeters measure the time of flight of the laser pulses to determine the range of the target. The simplest altimeter receiver consists of a photodetector followed by a leading edge detector. A time interval unit (TIU) measures the time from the transmitted laser pulse to the leading edge of the received pulse as it crosses a preset threshold. However, the ranging error of this simple detection scheme depends on the received, pulse amplitude, pulse shape, and the threshold. In practice, the pulse shape and the amplitude are determined by the target target characteristics which has to be assumed unknown prior to the measurement. The ranging error can be improved if one also measures the pulse width and use the average of the leading and trailing edges (half pulse width) as the pulse arrival time. The ranging error becomes independent of the received pulse amplitude and the pulse width as long as the pulse shape is symmetric. The pulse width also gives the slope of the target. The ultimate detection scheme is to digitize the received waveform and calculate the centroid as the pulse arrival time. The centroid detection always gives unbiased measurement even for asymmetric pulses. In this report, we analyze the laser altimeter ranging errors for these three detection schemes using the Mars Orbital Laser Altimeter (MOLA) as an example.

Davidson, Frederic M.↗
DOE OSTI2021

Picosecond laser generated plasma as a source of singly charged ions for external injection into an EBIS

The focus of this paper is on practical aspects of ion generation by picosecond lasers as a source of low charge state ions for external injection of ions into an electron beam ion source (EBIS). For a ps-laser, compared to a ns-laser currently used at Relativistic Heavy Ion Collier Electron Beam Ion Source (RHIC EBIS), the influence of heat conductivity in the solid target is almost negligible, which results in a lower target consumption rate and less vacuum pressure rise. By using a laser with high repetition rate, it is possible to produce quasi continuous 1+ ion beams for periods of tens of milliseconds, making it possible to take advantage of the ability of the EBIS to accumulate ions in the “slow” injection capture mode. Producing such an ion pulse train is now feasible since ps-lasers with pulse energy up to 10 mJ and rep-rate up to 10 kHz have recently become commercially available. The advantages of this lower current accumulation scheme include: (1) easier beam transport due to lower space charge of lower beam currents required compared to the present single pulse fast injection scheme, (2) better EBIS pulse to pulse ion output stability since pulse to pulse ion variations of the laser source are averaged over a long train of laser pulses, and (3) the possible addition of an isotope separator in which rare beams could be produced and selected at run time from less expensive (unenriched) targets. We studied the properties of plasmas generated by a ps-laser with 1.27 mJ energy within an 8 ps pulse and a repetition rate up to 400 Hz at Argonne National Laboratory to investigate feasibility and specify parameters for a laser ion source for RHIC EBIS using a “slow” injection mode. Al, Ti, Cu, Nb, and Ta targets were tested with various target translation speeds. Here, we demonstrated that a both “slow” and “fast” injection modes are accessible with a single ion source geometry and single injection line, providing the most attractive option for an ion source for external injection into RHIC EBIS trap based on a ps-laser.

43 PARTICLE ACCELERATORS↗
NASA NTRS2008

Range Imaging without Moving Parts

Range-imaging instruments of a type now under development are intended to generate the equivalent of three-dimensional images from measurements of the round-trip times of flight of laser pulses along known directions. These instruments could also provide information on characteristics of targets, including roughnesses and reflectivities of surfaces and optical densities of such semi-solid objects as trees and clouds. Unlike in prior range-imaging instruments based on times of flight along known directions, there would be no moving parts; aiming of the laser beams along the known directions would not be accomplished by mechanical scanning of mirrors, prisms, or other optical components. Instead, aiming would be accomplished by using solid-state devices to switch input and output beams along different fiber-optic paths. Because of the lack of moving parts, these instruments could be extraordinarily reliable, rugged, and long-lasting. An instrument of this type would include an optical transmitter that would send out a laser pulse along a chosen direction to a target. An optical receiver coaligned with the transmitter would measure the temporally varying intensity of laser light reflected from the target to determine the distance and surface characteristics of the target. The transmitter would be a combination of devices for generating precise directional laser illumination. It would include a pulsed laser, the output of which would be coupled into a fiber-optic cable with a fan-out and solid-state optical switches that would enable switching of the laser beam onto one or more optical fibers terminated at known locations in an array on a face at the focal plane of a telescope. The array would be imaged by the telescope onto the target space. The receiver optical system could share the aforementioned telescope with the transmitter or could include a separate telescope aimed in the same direction as that of the transmitting telescope. In either case, light reflected from the target would be focused by the receiver optical system onto an array of optical fibers matching the array in the transmitter. These optical fibers would couple the received light to one or more photodetector( s). Optionally, the receiver could include solid-state optical switches for choosing which optical fiber(s) would couple light to the photodetector(s). This instrument architecture is flexible and can be optimized for a wide variety of applications and levels of performance. For example, it is scalable to any number of pixels and pixel resolutions and is compatible with a variety of ranging and photodetection methodologies, including, for example, ranging by use of modulated (including pulsed and encoded) light signals. The use of fixed arrays of optical fibers to generate controlled illumination patterns would eliminate the mechanical complexity and much of the bulk of optomechanical scanning assemblies. Furthermore, digital control of the selection of the fiber-optic pathways for the transmitted beams could afford capabilities not seen in previous three-dimensional range-imaging systems. Instruments of this type could be specialized for use as, for example, proximity detectors, three-dimensional robotic vision systems, airborne terrain-mapping systems, and inspection systems.

Blair, J. Bryan↗
NASA NTRS1996

Soft X-Ray Optics by Pulsed Laser Deposition

Mo/Si and C/Co multilayers for soft x-ray optics were designed for spectral regions of interest in possible applications. Fabrication was effected by Pulsed Laser Deposition using Nd:YAG (355 nm) or excimer (248 nm) lasers in order to evaluate the suitability of this technique. Results for Mo/Si structures were not considered satisfactory due mainly to problems with particulate production and target surface modification during Si ablation. These problems may be alleviated by a two-wavelength approach, using separate lasers for each target. Results for C/Co multilayers are much more encouraging, since indication of good layering was observed for extremely thin layers. We expect to continue investigating this possibility. In order to compete with traditional PVD techniques, it is necessary to achieve film coverage uniformity over large enough areas. It was shown that this is feasible, and novel means of achieving it were devised.

Fernandez, Felix E.↗
DOE OSTI2021

Measurements of dynamic surface changes by digital holography for in situ plasma erosion applications

There are currently few viable diagnostic techniques for in situ measurement of plasma facing component erosion. Digital holography is intended to fill this gap. Progress on the development of single and dual CO 2 laser digital holography diagnostics for in situ plasma facing component erosion is discussed. The dual laser mode’s synthetic wavelength allows the measurable range to be expanded by a factor of ~400 compared to single laser digital holography. This allows the diagnostic to measure surface height changes of up to 4.5 μm in single laser mode and up to 2 mm in dual laser mode. Results include ex situ measurements of plasma eroded targets and also dynamic measurements of nm and μm scale motion of a target mounted on a precision translation stage. Dynamic measurements have successfully been made with the system operating in both single and dual laser modes, from ~50 nm to ~4 μm in single laser mode and up to ~400 μm in dual laser mode (limited only by the stage speed and camera acquisition duration). These results demonstrate the feasibility of using digital holography to characterize plasma facing component erosion dynamically, i.e., during plasma exposure. Results of proof-of-principle in situ digital holographic measurements of targets exposed to an electrothermal arc plasma source are presented.

Smith, Cary↗
DOE OSTI2023

Collisionless relativistic magnetic reconnection driven by electron vortices in laser-plasma interaction

Magnetic reconnection (MR) is a fundamental process in space and laboratory plasmas. The appearance of high power lasers opens a new way to investigate MR under the relativistic condition. In this paper, relativistic collisionless MR driven by two ultra-intense lasers and a pair of asymmetric targets is studied numerically via the kinetic simulations. The static magnetic fields produced by the electron vortex structures with opposite magnetic polarities approach each other driven by the magnetic pressure and the density gradient. The antiparallel magnetic fields annihilate accompanied with the topological variation and the corresponding magnetic field energy is being dissipated to the kinetic energy of the nonthermal charged particles. Besides the outflows along the current sheet, a fast particle bunch is accelerated perpendicularly contributed by the displacement current.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗