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At least 37 records · Page 2

High-energy X-ray radiography with apodized petawatt laser beams

We have produced laser wakefield-accelerated electron beams with energies of 2 GeV in Target Area 1 of the ZEUS facility. These electron beams oscillate in the accelerating structure that is produced in the wake of an ultrashort laser pulse (25 fs). These ’betatron’ oscillations result in the emission of a collimated (4 mrad divergence) beam of high-energy X-ray/gamma photons (on the order of several hundred keV). In this work, we demonstrate the capabilities of the ZEUS laser system by showing that apodizing the laser beam in the near field allows for the production of high-quality betatron X-rays for radiography purposes. This demonstrates that a high-power, large-aperture laser beam could be split into multiple parts to drive betatron X-ray sources from multiple angles or temporal delays into a High Energy Density (HED) target to be probed, enabling pump-probe measurements at multiple temporal delays or tomography on a single shot.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗

Z-Petawatt Laser Highlights for FY21

We’re happy to report that the full-aperture upgrade project, started in FY18, is now complete and short-pulse target experiments are underway. The table below lists the present performance level of ZPW. Additional laser improvements are in progress to increase the laser energy and pulse contrast along with implementing a correction for achromatic aberrations to reduce the focused spot size and pulse width.

47 OTHER INSTRUMENTATION↗

Designing Damage-Resistant Multilayer Dielectric Gratings for Petawatt-Class Lasers

We have successfully developed high efficiency dielectric gratings for chirped pulse amplification (CPA) pulse compression with a focus on improving damage thresholds for high peak power. Specifically, we focused on developing first-of-kind designs that operate at TM polarization. Unpublished modeling within our group shows that the electric field enhancement in the solid material for gratings operating at TM can be significantly less than for TE. Subsequently, the laser damage threshold of TM gratings should be higher by potentially a factor of 2X.

42 ENGINEERING↗

Particle Beam Acceleration Using 3 Petawatt Laser Pulses

The Zettawatt-Equivalent Ultrashort pulse laser System (ZEUS) is presently operational at the Gerard Mourou Center for Ultrafast Optical Science (CUOS) at the University of Michigan. ZEUS is a significant upgrade of the previous high power laser systems at CUOS and consists of two beamlines thatoperate in perfect synchronization. The 500 TW beamline became operational in 2023, 2 PW operation started in 2025 and full 3 PW power levels will be available in 2026. It is presently the highest power laser system in the US. In this grant the high field science group at CUOS has leveraged this unique high power laser facility to investigate laser wake field acceleration (LWFA) in ultra-high power laser plasma interactions and have shown how this can scale for future electron–positron colliders at high energy. The dual beam experimental configuration enables flexibility for many frontier experiments in laser-driven acceleration research, in particular, enabling extended channelling/acceleration experiments, positron generation/acceleration experiments and proof-of-principle transverse pumping “dephasingless” electron acceleration experiment and theory. LWFA may be able to miniaturize particle accelerators for high energy physics and also enable new sources of ultrafast, extreme brightness and precise x-rays for a wide variety of applications. In laser wake field acceleration, an electron bunch “surfs” on the electron plasma wave (the “wake field”) generated by the ponderomotive force of an intense laser. The plasma wave has a strong longitudinal electric field that stays in phase with the relativistic driver. A relativistic charged particle may, therefore, remain in phase with the accelerating field over long distances and gain ultra-relativistic energies. The accelerating electric field strength that the plasma wave can support can be many orders of magnitude higher than that of conventional accelerators, which makes laser wakefield acceleration an exciting prospect as an advanced accelerator concept. In this research project we have investigated the scaling of this mechanism to laser powers of 2 PW and have measured the x-ray emission and radio frequency emission resulting from the acceleration process. We have also performed theoretical investigation of mechanisms to scale laser driven accelerators to much higher energy using dephasingless acceleration processes.

43 PARTICLE ACCELERATORS↗

Laser Network US Experiments at the University of Texas at Austin

Under Subcontract B638654, The University of Texas at Austin (UT Austin) Center for High Energy Density Science supported three Laser Network US experiments and conducted upgrade planning for the Texas Petawatt Laser Facility. For the experiment “Investigation of the physics of MeV X-ray and particle generation using Compound Parabolic Concentrators” led by Dr. Andrew Mackinnon of Lawrence Livermore National Laboratory, UT Austin provided postdoctoral associate support in the person of Dr. Ganesh Tiwari. For the experiments “Megatesla magnetic fields and enhanced gamma-ray beam generation” led by Hans Rinderknecht of LLE, University of Rochester (experiment) and Alexey Arefiev of UC San Diego (theory) and “High resolution imaging of resonately accelerated electrons under tight focusing” led by Deepak Kumar of ELI-Beamlines, Czech Republic, UT Austin provided the Texas Petawatt Laser staff and a prorated share of the materials and supplies approximately equal to the average of those required for one 5-week experimental campaign. Summaries of these three experiments are provided in this report. Two staff members were hired—Dr. Sandra Bruce at 40% and Dr. Erhard Gaul at 50% time—to support Texas Petawatt Laser maintenance and operations and to plan for the Texas Relativistic Intensity Ultrafast Multi-beam Plasma Facility (TRIUMPF).

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗

X-ray Conversion Efficiencies for Diffraction Experiments on Z

We have used a deep-depletion CCD camera in single-hit mode to measure X-ray conversion efficiencies with Z-Beamlet and Z-Petawatt. Z-Petawatt is superior to Z-Beamlet for X-rays harder than 10 keV. For diffraction samples with Z > 42, we likely require X-rays with 15 keV or higher photon energy (Z-Petawatt). We are developing a robust, reproducible setup for X-ray polycapillaries as a part for X-ray diffraction experiments (XRD).

Geissel, Matthias↗

Pointing stabilization of a 1 Hz high-power laser via machine learning

Abstract High-power lasers are vital for particle acceleration, imaging, fusion and materials processing, requiring precise control and high-energy delivery. Laser plasma accelerators (LPAs) demand laser positional stability at focus to ensure consistent electron beams in applications such as X-ray free-electron lasers and high-energy colliders. Achieving this stability is especially challenging for the low-repetition-rate lasers in current LPAs. We present a machine learning method that predicts and corrects laser pointing instabilities in real-time using a high-frequency pilot beam. By preemptively adjusting a correction mirror, this approach overcomes traditional feedback limits. Demonstrated on the BELLA petawatt laser operating at the terawatt level (30 mJ amplification), our method achieved root mean square pointing stabilization of 0.34 and 0.59 $\unicode{x3bc} \mathrm{rad}$ in the x and y directions, reducing jitter by 65% and 47%, respectively. This is the first successful application of predictive control for shot-to-shot stabilization in low-repetition-rate laser systems, paving the way for full-energy petawatt lasers and transformative advances across science, industry and security.

Amodio, Alessio↗

LaserNetUS. Final report

In this proposal we have formed a consortium in response to a request from the DoE Office of Fusion Energy Sciences to establish a national network of Petawatt-class laser systems to act as domestic user facilities that can enable a broad range of frontier scientific research. This new entity is called LaserNet US. The network formed here is directly responsive to recommendations made in a recently released National Academy of Sciences Report with regard to US strategy for high intensity laser research, “Opportunities in Intense Ultrafast Lasers: Reaching for the Brightest Light”. As detailed in this report, the research in this area has the potential to transform science in a number of research fields and to open up new areas of fundamental research. High field science was initiated in the US in the 1990’s, and subsequently Europe and Asia have embraced this research field, investing more than a billion dollars in this area over the past several years. Our network includes five academic and two national lab-based high intensity laser facilities. These facilities are distributed geographically throughout the US and the network provides access to complementary facilities which have unique world-class laser and experimental capabilities. LaserNet US will make these existing Petawatt-class laser facilities available to users from around the country who until now have not had regular access to such machines. Consequently, the network, which will develop over time, will also become a key element in driving forward national research in high field and high energy density plasma science. In particular, the University of Michigan provides access to the Hercules laser facility and the T-cubed laser facility for collaborative experiments as part of the first year operation. In the second year - to begin in summer 2019 - the experiments will be chosen via proposal submission and review by an outside panel formed by DOE.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗

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↗

Towards High-Repetition-Rate Fast Neutron Sources Using Novel Enabling Technologies

High-flux, high-repetition-rate neutron sources are of interest in studying neutron-induced damage processes in materials relevant to fusion, ultimately guiding designs for future fusion reactors. Existing and upcoming petawatt laser systems show great potential to fulfill this need. Here, we present a platform for producing laser-driven neutron beams based on a high-repetition-rate cryogenic liquid jet target and an adaptable stacked lithium and beryllium converter. Selected ion and neutron diagnostics enable monitoring of the key parameters of both beams. A first single-shot proof-of-principle experiment successfully implemented the presented platform at the Texas Petawatt Laser facility, achieving efficient generation of a forward-directed neutron beam. This work lays the foundation for future high-repetition-rate experiments towards pulsed, high-flux, fast neutron sources for radiation-induced effect studies relevant for fusion science and applications that require neutron beams with short pulse duration.

47 OTHER INSTRUMENTATION↗

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↗

Multi-probe meeting with Harwell II: A discussion of potential areas of cooperation for mutual benefit by the LANL Multi-probe Radiography team [Slides]

In this presentation, we continue a discussion begun in September 2023, with staff from the University of Manchester and the Central Laser Facility-Harwell in the UK exploring the possibilities for cooperative work of mutual interest in the technology underpinning petawatt laser driven Multi-Probe radiography. Since the September Seminar, the US and UK staff have exchanged lists of ideas for possible cooperation and this presentation comprises brief descriptions of five topics that LANL staff would offer for consideration in the area of laser driven radiation sources, applications of machine learning and experiments at Omega (in the US) and Gemini (in the UK).

62 RADIOLOGY AND NUCLEAR MEDICINE↗

High-power non-perturbative laser delivery diagnostics at the final focus of 100-TW-class laser pulses

Controlling the delivery of multi-terawatt and petawatt laser pulses to final focus, both in position and angle, is critical to many laser applications such as optical guiding, laser–plasma acceleration, and laser-produced secondary radiation. We present an online, non-destructive laser diagnostic, capable of measuring the transverse position and pointing angle at focus. The diagnostic is based on a unique double-surface-coated wedged-mirror design for the final steering optic in the laser line, producing a witness beam highly correlated with the main beam. By propagating low-power kilohertz pulses to focus, we observed spectra of focus position and pointing angle fluctuations dominated by frequencies below 70 Hz. The setup was also used to characterize the excellent position and pointing angle correlation of the 1 Hz high-power laser pulses to this low-power kilohertz pulse train, opening a promising path to fast non-perturbative feedback concepts even on few-hertz-class high-power laser systems.

47 OTHER INSTRUMENTATION↗

MTW-OPAL: a technology development platform for ultra-intense optical parametric chirped-pulse amplification systems

Optical parametric chirped-pulse amplification implemented using multikilojoule Nd:glass pump lasers is a promising approach for producing ultra-intense pulses (>10 23 W/cm 2 ). We report on the MTW-OPAL Laser System, an optical parametric amplifier line (OPAL) pumped by the Nd:doped portion of the multi-terawatt (MTW) laser. This midscale prototype was designed to produce 0.5-PW pulses with technologies scalable to tens of petawatts. Technology choices made for MTW-OPAL were guided by the longer-term goal of two full-scale OPALs pumped by the OMEGA EP to produce 2 × 25-PW beams that would be co-located with kilojoule–nanosecond ultraviolet beams. Several MTW-OPAL campaigns that have been completed since “first light” in March 2020 show that the laser design is fundamentally sound, and optimization continues as we prepare for “first-focus” campaigns later this year.

42 ENGINEERING↗

Laser-driven x-ray and proton micro-source and application to simultaneous single-shot bi-modal radiographic imaging

Radiographic imaging with x-rays and protons is an omnipresent tool in basic research and applications in industry, material science and medical diagnostics. The information contained in both modalities can often be valuable in principle, but difficult to access simultaneously. Laser-driven solid-density plasma-sources deliver both kinds of radiation, but mostly single modalities have been explored for applications. Their potential for bi-modal radiographic imaging has never been fully realized, due to problems in generating appropriate sources and separating image modalities. Here, we report on the generation of proton and x-ray micro-sources in laser-plasma interactions of the focused Texas Petawatt laser with solid-density, micrometer-sized tungsten needles. We apply them for bi-modal radiographic imaging of biological and technological objects in a single laser shot. Thereby, advantages of laser-driven sources could be enriched beyond their small footprint by embracing their additional unique properties, including the spectral bandwidth, small source size and multi-mode emission.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗

Ultra-short pulse laser acceleration of protons to 80 MeV from cryogenic hydrogen jets tailored to near-critical density

Laser plasma-based particle accelerators attract great interest in fields where conventional accelerators reach limits based on size, cost or beam parameters. Despite the fact that particle in cell simulations have predicted several advantageous ion acceleration schemes, laser accelerators have not yet reached their full potential in producing simultaneous high-radiation doses at high particle energies. The most stringent limitation is the lack of a suitable high-repetition rate target that also provides a high degree of control of the plasma conditions required to access these advanced regimes. Here, we demonstrate that the interaction of petawatt-class laser pulses with a pre-formed micrometer-sized cryogenic hydrogen jet plasma overcomes these limitations enabling tailored density scans from the solid to the underdense regime. Our proof-of-concept experiment demonstrates that the near-critical plasma density profile produces proton energies of up to 80 MeV. Based on hydrodynamic and three-dimensional particle in cell simulations, transition between different acceleration schemes are shown, suggesting enhanced proton acceleration at the relativistic transparency front for the optimal case.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗