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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 163 records · Page 9
All sourcesNASA NTRSDOE OSTI
DOE OSTI2022

How transient effects can change the inferred plasma temperatures when using K-shell sulfur line ratios in a time dependent iron sulfide plasma

This paper describes how the steady state atomic kinetics approximation can underestimate the electron temperature determined from K-shell lines in ps-time-scale transient plasmas. In particular, we model the temperature determination of solid FeS targets used in opacity experiments at the Orion laser facility from the ratio of sulfur He-α to Ly-α lines. Such experiments use short-pulse lasers to heat a thin microdot of FeS buried in a plastic target to temperatures of more than 1 keV and densities of approximately 1–2 g/cm 3 . Using atomic kinetics calculations based on a temperature history from a radiation hydrodynamic simulation of the target evolution, the peak temperature inferred from the sulfur line ratios is 1.29 keV at 3.1 ps as compared with the input peak temperature of 1.41 keV at 2.0 ps. There is a time lag of 1.2 ps at the peak, and an overall 0.5 ps time lag in the temporal history of the temperature as the plasma cools over the next 10 ps.

Rilloraza, Francisco↗
DOE OSTI2020

2 H(p,γ) 3 He cross section measurement using high-energy-density plasmas

An absolute cross section for the radiative capture reaction 2 H(p,γ) 3 He has been measured at the OMEGA laser facility using inertially confined plasmas. These high-temperature plasmas are created by imploding a fuel-containing capsule using laser ablation, and are advantageous in that they better mimic astrophysical systems. We measure an S factor for this reaction of 0.429 ± 0.026 stat ± 0.072 sys eV b at E c.m . = 16.35 ± 0.40 keV, which is higher than the adopted evaluations. Furthermore, this reaction is important as a source of nuclear energy in protostars and brown dwarfs. It is also a critical reaction during big-bang nucleosynthesis, and an accurate cross section can be used as a constraint on cosmology.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2024

A Scalable, High-Efficiency, Low-Energy-Spread Laser Wakefield Accelerator Using a Tri-Plateau Plasma Channel

The emergence of multi-petawatt laser facilities is expected to push forward the maximum energy gain that can be achieved in a single stage of a laser wakefield acceleration (LWFA) to tens of giga-electron volts, which begs the question—is it likely to impact particle physics by providing a truly compact particle collider? Colliders have very stringent requirements on beam energy, acceleration efficiency, and beam quality. In this article, we propose an LWFA scheme that can for the first time simultaneously achieve hitherto unrealized acceleration efficiency from the laser to the electron beam of >20% and a sub-1% energy spread using a stepwise plasma structure and a nonlinearly chirped laser pulse. Three-dimensional high-fidelity simulations show that the nonlinear chirp can effectively mitigate the laser waveform distortion and lengthen the acceleration distance. This, combined with an interstage rephasing process in the stepwise plasma, can triple the beam energy gain compared to that in a uniform plasma for a fixed laser energy, thereby dramatically increasing the efficiency. A dynamic beam loading effect can almost perfectly cancel the energy chirp that arises during the acceleration, leading to the sub-percent energy spread. This scheme is highly scalable and can be applied to petawatt LWFA scenarios. Scaling laws are obtained, which suggest that electron beams with parameters relevant for a Higgs factory could be reached with the proposed high-efficiency, low-energy-spread scheme.

43 PARTICLE ACCELERATORS↗
DOE OSTI2022

Scaling of laser-driven electron and proton acceleration as a function of laser pulse duration, energy, and intensity in the multi-picosecond regime

A scaling study of short-pulse laser-driven proton and electron acceleration was conducted as a function of pulse duration, laser energy, and laser intensity in the multi-picosecond (ps) regime (∼0.8 ps–20 ps). Maximum proton energies significantly greater than established scaling laws were observed, consistent with observations at other multi-ps laser facilities. In addition, maximum proton energies and electron temperatures in this regime were found to be strongly dependent on the laser pulse duration and preplasma conditions. A modified proton scaling model is presented that is able to better represent the accelerated proton characteristics in this multi-ps regime.

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↗
DOE OSTI2022

On the control of electron heating for optimal laser radiation pressure ion acceleration

We study the onset of electron heating in intense laser–solid interactions and its impact on the spectral quality of radiation pressure accelerated ions in both hole boring and light sail regimes. Two- and three-dimensional particle-in-cell (PIC) simulations are performed over a wide range of laser and target parameters and reveal how the pulse duration, profile, polarization and target surface stability control the electron heating, the dominant ion acceleration mechanisms and the ion spectra. We find that the onset of strong electron heating is associated with the growth of the Rayleigh–Taylor-like instability at the front surface and must be controlled to produce high-quality ion beams, even when circularly polarized lasers are employed. We define a threshold condition for the maximum duration of the laser pulse that allows mitigation of electron heating and radiation pressure acceleration of narrow energy spread ion beams. The model is validated by three-dimensional PIC simulations, and the few experimental studies that reported low energy spread radiation pressure accelerated ion beams appear to meet the derived criteria. The understanding provided by our work will be important in guiding future experimental developments, for example for the ultrashort laser pulses becoming available at state-of-the-art laser facilities, for which we predict that proton beams with $\sim$ 150–250 MeV, $\sim$ 30% energy spread, and a total laser-to-proton conversion efficiency of $\sim$ 20% can be produced.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2025

Measurement of directional muon beams generated at the Berkeley Lab Laser Accelerator

We present the detection of directional muon beams produced using a PW laser facility at the Lawrence Berkeley National Laboratory. The muon source is a multi-GeV electron beam generated in a laser-plasma accelerator interacting with a high- converter target. The GeV photons resulting from the interaction are converted into a high-flux, directional muon beam via pair production. By employing scintillators to capture delayed events, we were able to identify the produced muons and characterize the source. Using theoretical knowledge of the muon production process combined with simulations that are in excellent agreement with the experiments, we demonstrate that laser-plasma accelerators have the capability of generating electron beams with characteristics suitable to produce GeV-scale muons that offer unique advantages with respect to the cosmic background. Laser-plasma-accelerator-based muon sources can therefore enhance muon imaging applications thanks to their compactness, directionality, and high yields, which reduce the exposure time by orders of magnitude compared to cosmic ray muons. Using the eant4-based simulation code we developed to gain insight into the experimental results, we can design future experiments and applications based on LPA-generated muons.

Terzani, Davide↗
DOE OSTI2022

Argon equation of state data to 1 TPa: Shock compression experiments and simulations

Argon is the most abundant noble gas on Earth and its noble, atomic fluid nature makes it an excellent candidate for comparison of experiment and theory at extreme conditions. For this study, we performed a combined computational and experimental study on shock compressed cryogenic liquid argon. Using Sandia's Z machine, we shock compressed liquid argon to 600 GPa and reshock states up to 950 GPa. Laser shock experiments at the Omega Laser facility extend the principal Hugoniot to 1000 GPa and provided temperature data along the principal Hugoniot. The plate impact experiments and laser shock experiments used well-characterized impedance matching standards and demonstrate consistent results between the two platforms over a common range. Density functional theory based molecular dynamics simulations provided additional data on the Hugoniot to 600 GPa. The combined experimental data and simulation results provide constraints on the development of new equation of state models at extreme conditions.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2021

Pump-depletion dynamics and saturation of stimulated Brillouin scattering in shock ignition relevant experiments

As an alternative inertial confinement fusion scheme, shock ignition requires a strong converging shock driven by a high-intensity laser pulse to ignite a pre-compressed fusion capsule. Understanding nonlinear laser-plasma instabilities is crucial to assess and improve the laser-shock energy coupling. Recent experiments conducted on the OMEGA EP laser facility have for the first time demonstrated that such instabilities can 100% deplete the first 0.5 ns of the high-intensity laser. Here, analyses of the observed laser-generated blast wave suggest that this pump-depletion starts at 0.02 critical density and progresses to 0.1-0.2 critical density, which is also confirmed by the time-resolved stimulated Raman backscattering spectra. The pump-depletion dynamics can be explained by the breaking of ion-acoustic waves in stimulated Brillouin scattering. Such pump-depletion would inhibit the collisional laser energy absorption but may benefit the generation of hot electrons with moderate temperatures for electron shock ignition.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2020

Demonstration of a 2 ps, 5 TW peak power, long-wave infrared laser based on chirped-pulse amplification with mixed-isotope CO 2 amplifiers 2 amplifiers

We report generation of 5 TW peak power in a 2 ps pulse at 9.2 µm via chirped-pulse amplification (CPA) in mixed-isotope high-pressure CO 2 laser amplifiers. This represents the highest peak power in a single picosecond pulse format and the shortest pulse at terawatt peak power ever achieved in the long-wave infrared (LWIR) spectral range. Maximum demonstrated energy of the compressed pulse is 14 J and minimum period between shots is 20 s. The successful implementation of the chirped pulse amplification technique in a short-pulse gas laser opens a route to development of LWIR laser facilities with tens of terawatts of peak power, thus approaching the number of photons per optical cycle of current near-infrared laser systems based on solid-state active media.

43 PARTICLE ACCELERATORS↗
DOE OSTI2023

Final Scientific Report on: Magnetized Shock Physics and Convergent Flows

The objective of this project was to study magnetized shocks in plasmas using the Omega Laser Facility to drive a solid foil into a magnetized gas, which would be preionized by the x-rays from the laser-solid interaction. The MIFEDS (magneto-inertial fusion electrical discharge system) provided the magnetic field. Magnetized shocks are of interest in magneto-inertial fusion, such as MagLIF and magnetized spherical implosions with both direct and indirect drive, space physics, heliophysics, and astrophysics. In magneto-inertial fusion the shocks of interest are collisional and perpendicular to the magnetic field lines, since the magnetic field needs to be compressed. In space, the shocks of interest are typically collisionless, due to the low plasma density, and both perpendicular and parallel to the magnetic field. The marginally collisionless regime between these is also of interest in both laboratory, fusion, and space plasmas, but has barely been investigated.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2022

Electron pulse train accelerated by a linearly polarized Laguerre–Gaussian laser beam

A linearly polarized Laguerre–Gaussian (LP-LG) laser beam with a twist index $l$ = –1 has field structure that fundamentally differs from the field structure of a conventional linearly polarized Gaussian beam. Close to the axis of the LP-LG beam, the longitudinal electric and magnetic fields dominate over the transverse components. This structure offers an attractive opportunity to accelerate electrons in vacuum. It is shown, using three-dimensional particle-in-cell simulations, that this scenario can be realized by reflecting an LP-LG laser off a plasma with a sharp density gradient. The simulations indicate that a 600 TW LP-LG laser beam effectively injects electrons into the beam during the reflection. The electrons that are injected close to the laser axis experience a prolonged longitudinal acceleration by the longitudinal laser electric field. The electrons form distinct monoenergetic bunches with a small divergence angle. The energy in the most energetic bunch is 0.29 GeV. The bunch charge is 6 pC and its duration is approximately 270 as. The divergence angle is just 0.57° (10 mrad). By using a linearly polarized rather than a circularly polarized Laguerre–Gaussian beam, our scheme makes it easier to demonstrate the electron acceleration experimentally at a high-power laser facility.

43 PARTICLE ACCELERATORS↗
DOE OSTI2026

Ionization and temperature measurements in warm dense copper using x-ray absorption spectroscopy

We detail experimental results inferring ionization and temperature for warm dense copper plasmas at several times solid density (15–25 g/cm 3 ) and temperatures of 10–21 eV. Experiments performed at the OMEGA Laser Facility generate uniform warm dense matter conditions via symmetric shock compression of a buried copper layer. The plasma is probed with a laser-generated x-ray source to collect the K-shell x-ray absorption spectrum. Fitting bound-bound absorption contributions from constituent charge states of copper provides an estimated $\overline{Z}$ of approximately 4–7 for these warm dense copper plasmas. We find that these partially ionized plasmas have K-edge shifts of 12–30 eV and bound-bound resonance 1s → 3p absorption shifts of 4–26 eV with respect to the cold K edge. This study provides necessary experimental data to improve ionization and opacity models in the warm dense matter regime.

42 ENGINEERING↗
NASA NTRS1990

Shuttle Laser Technology Experiment Facility (LTEF)-to-airplane lasercom experiment: Airplane considerations

NASA is considering the use of various airplanes for a Shuttle Laser Technology Experiment Facility (LTEF)-to-Airplane laser communications experiment. As supporting documentation, pertinent technical details are included about the potential use of airplanes located at Ames Research Center and Wallops Flight Facility. The effects and application of orbital mechanics considerations are also presented, including slant range, azimuth, elevation, and time. The pros and cons of an airplane equipped with a side port with a bubble window versus a top port with a dome are discussed.

Kalil, Ford↗
DOE OSTI2021

Expanded Capabilities and Opportunities for Virtual Beamline Code

In the 25 years since LLNL broke ground on the National Ignition Facility (NIF) - a cornerstone of the National Nuclear Security Administration’s Stockpile Stewardship Program - the NIF and Photon Science (NIF&PS) Directorate has steadily pushed the boundaries of laser physics, nonlinear optics, and photonics in service of inertial confinement fusion experiments, and advanced photon sources development. Beyond the 192 beamlines of the primary laser facility with its world-record energy and fusion yields, NIF&PS capabilities have expanded to include chirped-pulse amplification, kilojoule petawatt-class short-pulse systems to generate hard x-ray radiographic probes, high-average power lasers as secondary sources for generation or wake field particle acceleration along directed energy applications, and other scientific pursuits. The Computing Directorate partners with NIF&PS on numerous projects and technologies from diagnostic measurements and high performance control systems to data analysis, information technology infrastructure, and scientific simulation code development. “This strong collaboration enables cutting-edge science, particularly with regard to physics-based modeling and simulation,” says physicist Jean-Michel Di Nicola. One crucial capability for NIF&PS is the Virtual Beamline (VBL) laser simulation code. It can model all the major laser physics and technology involved in the design optimization, commissioning, and operations of advanced laser architectures from tabletop to NIF-scale. VBL provides researchers with high-fidelity models and high-resolution calculations of laser performance predictions—including for the entire NIF laser system, the Advanced Radiographic Capability, parts of the High Repetition-Rate Advanced Petawatt Laser System laser delivered to the Czech Republic, and the Optical Science Laser. After more than two decades of experimentally verified physics and computing enhancements, this unique workhorse code is wrapping up another major milestone: migration from Java to C++ with a flurry of user interface and optimization features, as well as laser physics and high-resolution enhancements thanks to parallel execution on Livermore Computing platforms.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
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↗
DOE OSTI2021

Electron energization during merging of self-magnetized, high-beta, laser-produced plasmas

Electron energization during merging of magnetized plasmas is studied using the OMEGA and OMEGA EP laser facilities by colliding two plasma plumes, each containing a Biermann-battery self-generated magnetic field. Two neighbouring plasma plumes are produced by intense laser beams, and the anti-parallel Biermann fields merge and reconnect in the process of the plumes’ expansion and collision. To isolate the merging as an acceleration source, the electron energy spectra obtained from two-plume collision shots are compared with the spectra from single-plume shots. Single-plume shots exhibit an energized electron tail with energies up to ${\sim }250\ \textrm {keV}$ . The electrons in merging experiments are additionally accelerated by ${\sim }50\text {--}100$ keV compared to single-plume shots.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2026

Suppression and enhancement of electromagnetic pulses from laser–target interactions by strong magnetic fields

Laser–target interactions generate intense electromagnetic pulses (EMPs) that can interfere with measurements and damage equipment. In this paper we show that applying a magnetic field to nanosecond pulse laser–target interactions decreases the magnitude of EMPs. We demonstrate this effect in two experiments with different geometries (spherical versus planar), laser intensities ( ∼10 13 versus ∼10 15 W/cm 2 ) and applied field strength (12 versus 0.1 T) that both observed suppression of EMPs in approximately the 1 GHz band (by factors of 0.65× and 0.32×, respectively). We then observe the opposite effect at high intensities with a picosecond pulse: for planar experiments with laser intensities of approximately 10 19 W/cm 2 and magnetic fields of 6–10 T, the magnitude of EMPs is increased by a factor of 1.75×. These results provide a benchmark for models of EMP generation, but suggest that magnetic fields are not a viable solution for mitigating EMPs in the high-intensity laser facilities where they are most damaging.

electromagnetic pulse↗