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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 37 records · Page 2
All sourcesNASA NTRSDOE OSTI
DOE OSTI2021

Proton beam quality enhancement by spectral phase control of a PW-class laser system

We report on experimental investigations of proton acceleration from solid foils irradiated with PW-class laser-pulses, where highest proton cut-off energies were achieved for temporal pulse parameters that varied significantly from those of an ideally Fourier transform limited (FTL) pulse. Controlled spectral phase modulation of the driver laser by means of an acousto-optic programmable dispersive filter enabled us to manipulate the temporal shape of the last picoseconds around the main pulse and to study the effect on proton acceleration from thin foil targets. The results show that applying positive third order dispersion values to short pulses is favourable for proton acceleration and can lead to maximum energies of 70 MeV in target normal direction at 18 J laser energy for thin plastic foils, significantly enhancing the maximum energy compared to ideally compressed FTL pulses. The paper further proves the robustness and applicability of this enhancement effect for the use of different target materials and thicknesses as well as laser energy and temporal intensity contrast settings. We demonstrate that application relevant proton beam quality was reliably achieved over many months of operation with appropriate control of spectral phase and temporal contrast conditions using a state-of-the-art high-repetition rate PW laser system.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2024

Design, tuning, and blackbox optimization of laser systems

Chirped pulse amplification (CPA) and subsequent nonlinear optical (NLO) systems constitute the backbone of myriad advancements in semiconductor manufacturing, communications, biology, defense, and beyond. Accurately and efficiently modeling CPA+NLO-based laser systems is challenging because of the complex coupled processes and diverse simulation frameworks. Our modular start-to-end model unlocks the potential for exciting new optimization and inverse design approaches reliant on data-driven machine learning methods, providing a means to create tailored CPA+NLO systems unattainable with current models. To demonstrate this new, to our knowledge, technical capability, we present a study on the LCLS-II photo-injector laser, representative of a high-power and spectro-temporally non-trivial CPA+NLO system.

47 OTHER INSTRUMENTATION↗
DOE OSTI2025

Identification of contamination in the pulse-compression chamber of the OMEGA EP Laser System originating from clean room garments

The contamination of optical components with microscopic particles strongly impacts their ability to handle high-power or high-intensity laser pulses via an array of mechanisms. This work explores the nature and origin of a subset of contamination particles found inside the pulse-compression chamber of the OMEGA EP Laser System. Using Raman microscopy accompanied by other analytical methods, it was shown that sodium nitrate constitutes a significant fraction of the particles that possess diameters on the order of a few micrometers. Further investigation aiming to reveal the origin of these particles suggests that these sodium nitrate particles are deposited via shedding from the reusable clean room garments worn in the Laser Bay and compression chamber. Raman microscopy also revealed various plastic particles such as polystyrene, polyethylene, and poly(diallyl isophthalate).

Raman spectroscopy↗
DOE OSTI2022

Demonstration of a side-pumped cross-seeded thin-slab pre-amplifier for high-power Ti:Sa laser systems

Here, we demonstrate a room-temperature Ti:Sapphire (Ti:Sa) amplifier that uses a cross pump-seed geometry (cross-thin-slab) to generate 30-mJ output pulses at 0.5-kHz repetition rate, and 25 mJ at 1 kHz when pumped by 100-mJ, 515-nm pulses from a diode-pumped Yb:YAG laser. The geometry allows to maintain a crystal temperature of ~30°C using cooling water at 10°C. The amplifier is an attractive solution for use in the first stages of amplification in high peak and high average power chirped pulse amplification laser systems.

47 OTHER INSTRUMENTATION↗
DOE OSTI2020

A method to determine the electric field of liquid argon time projection chambers using a UV laser system and its application in MicroBooNE

Liquid argon time projection chambers (LArTPCs) are now a standard detector technology for making accelerator neutrino measurements, due to their high material density, precise tracking, and calorimetric capabilities. An electric field (E-field) is required in such detectors to 2020 JINST 15 P07010 drift ionization electrons to the anode where they are collected. The E-field of a TPC is often approximated to be uniform between the anode and the cathode planes. However, significant distortions can appear from effects such as mechanical deformations, electrode failures, or the accumulation of space charge generated by cosmic rays. The latter effect is particularly relevant for detectors placed near the Earth’s surface and with large drift distances and long drift time. To determine the E-field in situ, an ultraviolet (UV) laser system is installed in the MicroBooNE experiment at Fermi National Accelerator Laboratory. The purpose of this system is to provide precise measurements of the E-field, and to make it possible to correct for 3D spatial distortions due to E-field non-uniformities. Here we describe the methodology developed for deriving spatial distortions, the drift velocity and the E-field from UV-laser measurements.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2024

A six degrees of freedom femtosecond laser system for fabrication of small-scale mechanical property specimens

Here, we present the details of a novel ultra-short pulsed laser machining workstation that has been employed for high-throughput laser machining of small-scale mechanical property specimens. This system employs a six degrees of freedom hexapod positioning stage capable of macroscopic movements at high positional accuracy. We developed a methodology that uses quantitative image analysis to measure key parameters required to minimize the hexapod positioning and rotational error. Application of this system to laser machining of small-scale 316L stainless steel tensile specimens and ultra-high molecular weight polyethylene compressive specimens using eucentric tilt and rotation about the specimen axis will be shown, where serial laser milling at a specimen tilt angle of 10° was used to effectively eliminate any taper in the sample cross section that is typically found in laser machining.

47 OTHER INSTRUMENTATION↗
DOE OSTI2022

Mitigation of the harmful effects of stray-light reflections in high-energy laser systems

Reduction or elimination of negative consequences of reflected stray light from lens surfaces is achieved by propagating a laser beam through an eccentric pupil that excludes the optical axis of the system, which is rotationally symmetric. In such systems, stray light reflections eventually are focused onto the unique optical axis of the system, in either a real or virtual focal region. By using an eccentric pupil, all damage due to focusing of the stray light lies outside of the beam. These focal regions can, e.g., be physically blocked to eliminate beam paths that lead to optical damage, re-pulse beams and parasitic lasing.

Seppala, Lynn G.↗
DOE OSTI2025

The advent of third-harmonic-generation laser systems: personal recollections

In the mid to late 1970s there was considerable debate as to which laser technology should be pursued—glass lasers (1-μm wavelength) or CO 2 lasers (10 μm). Based on target-physics considerations, theorists were advocating for shorter wavelengths. The physics understanding was confirmed by exciting results from the group at the École Polytechnique, who observed close to 100% target absorption with just a few joules of fourth-harmonic energy. These results motivated the leadership at LLE to plan similar experiments at the third harmonic, with a few more joules. This presentation covers a small time period from 1979 to 1980 during which highly efficient Third-Harmonic Generation (THG) became understood theoretically and demonstrated experimentally, leading to the worldwide adoption of THG with glass lasers for fusion research.

47 OTHER INSTRUMENTATION↗
DOE OSTI2023

High-resolution laser system for the S 3 -Low Energy Branch

Here, in this paper we present the first high-resolution laser spectroscopy results obtained at the GISELE laser laboratory of the GANIL-SPIRAL2 facility, in preparation for the first experiments with the S 3 -Low Energy Branch. Studies of neutron-deficient radioactive isotopes of erbium and tin represent the first physics cases to be studied at S 3 . The measured isotope-shift and hyperfine structure data are presented for stable isotopes of these elements. The erbium isotopes were studied using the 4f 12 6s 2 3 H 6 → 4f 12 ( 3 H)6s6p J = 5 atomic transition (415 nm) and the tin isotopes were studied by the 5s 2 5p 2 ( 3 P 0 ) → 5s 2 5p6s( 3 P 1 ) atomic transition (286.4 nm), and are used as a benchmark of the laser setup. Additionally, the tin isotopes were studied by the 5s 2 5p6s( 3 P 1 ) → 5s 2 5p6p( 3 P 2 ) atomic transition (811.6 nm), for which new isotope-shift data was obtained and the corresponding field-shift F 812 and mass-shift M 812 factors are presented.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2022

Demonstration of plasma mirror capability for the OMEGA Extended Performance laser system

A plasma mirror platform was developed for the OMEGA-EP facility to redirect beams, thus enabling more flexible experimental configurations as well as a platform that can be used in the future to improve laser contrast. The plasma mirror reflected a short pulse focusing beam at 22.5° angle of incidence onto a 12.5 μm thick Cu foil, generating Bremsstrahlung and k α x rays, and accelerating ions and relativistic electrons. By measuring these secondary sources, the plasma mirror key performance metrics of integrated reflectivity and optical quality are inferred. It is shown that for a 5 ± 2 ps, 310 J laser pulse, the plasma mirror integrated reflectivity was 62 ± 13% at an operating fluence of 1670 J cm –2 , and that the resultant short pulse driven particle acceleration and x-ray generation indicate that the on target intensity was 3.1 × 10 18 W cm –2 , which is indicative of a good post-plasma mirror interaction beam optical quality. By deriving the plasma mirror performance metrics from the secondary source scalings, it was simultaneously demonstrated that the plasma mirror is ready for adoption in short pulse particle acceleration and high energy photon generation experiments using the OMEGA-EP system.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗