Jim Gaffney
A5056062979- Laser-Plasma Interactions and Diagnostics
- Laser-induced spectroscopy and plasma
- Nuclear Physics and Applications
- High-pressure geophysics and materials
- Energetic Materials and Combustion
- Laser-Matter Interactions and Applications
- Combustion and Detonation Processes
- Atomic and Molecular Physics
- Magnetic confinement fusion research
- Gaussian Processes and Bayesian Inference
- Model Reduction and Neural Networks
- Atomic and Subatomic Physics Research
- Computational Physics and Python Applications
- Generative Adversarial Networks and Image Synthesis
- Nuclear reactor physics and engineering
- Fusion materials and technologies
- Cell Image Analysis Techniques
- Gamma-ray bursts and supernovae
- Cold Fusion and Nuclear Reactions
- Ion-surface interactions and analysis
- Data Visualization and Analytics
- Topological and Geometric Data Analysis
- Scientific Computing and Data Management
- Advanced Optical Sensing Technologies
- Neural Networks and Applications
Lawrence Livermore National Laboratory
2013-2024
University of Rochester
2021
Energetics (United States)
2021
Purdue University System
2017
Hosparus
2017
Imperial College London
2009-2011
Abstract Obtaining a burning plasma is critical step towards self-sustaining fusion energy 1 . A one in which the reactions themselves are primary source of heating plasma, necessary to sustain and propagate burn, enabling high gain. After decades research, here we achieve burning-plasma state laboratory. These experiments were conducted at US National Ignition Facility, laser facility delivering up 1.9 megajoules pulses with peak powers 500 terawatts. We use lasers generate X-rays radiation...
High-harmonic generation is a universal response of matter to strong femtosecond laser fields, coherently upconverting light much shorter wavelengths. Optimizing the conversion into soft x-rays typically demands trade-off between two competing factors. Because reduced quantum diffusion radiating electron wave function, emission from each species highest when short-wavelength ultraviolet driving used. However, phase matching--the constructive addition x-ray waves large number atoms--favors...
Abstract In a burning plasma state 1–7 , alpha particles from deuterium–tritium fusion reactions redeposit their energy and are the dominant source of heating. This has recently been achieved at US National Ignition Facility 8 using indirect-drive inertial-confinement fusion. Our experiments use laser-generated radiation-filled cavity (a hohlraum) to spherically implode capsules containing deuterium tritium fuel in central hot spot where occur. We have developed more efficient hohlraums...
For many years, low mode asymmetry in inertially confined fusion (ICF) implosions has been recognized as a potential performance limiting factor, but analysis limited to using simulations and searching for data correlations. Herein, an analytically solvable model based upon the simple picture of asymmetric piston is presented. Asymmetry shell driving implosion, opposed hot-spot, key model. The provides unifying framework action mode-1 resulting connections between various diagnostic...
Data-driven science and technology offer transformative tools methods to science. This review article highlights the latest development progress in interdisciplinary field of data-driven plasma (DDPS), i.e., whose is driven strongly by data analyses. Plasma considered be most ubiquitous form observable matter universe. Data associated with plasmas can, therefore, cover extremely large spatial temporal scales, often provide essential information for other scientific disciplines. Thanks...
Abstract Indirect Drive Inertial Confinement Fusion Experiments on the National Ignition Facility (NIF) have achieved a burning plasma state with neutron yields exceeding 170 kJ, roughly 3 times prior record and necessary stage for igniting plasmas. The results are despite multiple sources of degradations that lead to high variability in performance. Results shown here, first time, include an empirical correction factor mode-2 asymmetry regime addition previously determined corrections...
The inertial confinement fusion program relies upon detailed simulations with (ICF) codes to design targets and interpret the experimental results. These treat as much physics from essential principles is practical, including laser deposition, cross beam energy transfer, x-ray production transport, nonlocal thermal equilibrium kinetics, hydrodynamic instabilities, thermonuclear burn, transport of reaction products. Improvements in radiation code capabilities vast increases computing power...
Machine learning is finding increasingly broad applications in the physical sciences. This most often involves building a model relationship between dependent, measurable output, and an associated set of controllable, but complicated, independent inputs. We present tutorial on current techniques machine learning—a jumping-off point for interested researchers to advance their work. focus deep neural networks with emphasis demystifying learning. begin background ideas some example from...
Computer models of inertial confinement fusion (ICF) implosions play an essential role in experimental design and interpretation as well our understanding fundamental physics under the most extreme conditions that can be reached laboratory. Building truly predictive is a significant challenge, with potential to greatly accelerate progress high yield ignition. One path more use data update underlying way extrapolated new experiments regimes. We describe statistical framework for calibration...
We describe the overall performance of major indirect-drive inertial confinement fusion campaigns executed at National Ignition Facility. With respect to proximity ignition, we can current experiments both in terms no-burn ignition metrics (metrics based on hydrodynamic targets absence alpha-particle heating) and thermodynamic properties hotspot dense fuel stagnation—in particular, pressure, temperature, areal density. a simple 1D isobaric model derive these quantities from experimental...
A simple 3D dynamic model for inertial confinement fusion (ICF) implosions has been developed and used to assess the impacts of low-mode asymmetry, aneurysms mix-induced radiative loss on capsule performance across ICF platforms. The model, while benchmarked against radiation hydrodynamics simulations, benefits from simplicity speed allow rapid assessment possible sources degradation as well help build intuition about relative importance different effects. Degradations in result areal...
We have developed an experimental platform for the National Ignition Facility that uses spherically converging shock waves absolute equation-of-state (EOS) measurements along principal Hugoniot. In this Letter, we present one indirect-drive implosion experiment with a polystyrene sample employs radiographic compression over range of pressures reaching up to 60 Mbar (6 TPa). This significantly exceeds previously published results obtained on Nova laser [R. Cauble et al., Phys. Rev. Lett. 80,...
Numerical simulations of high energy-density experiments require equation state (EOS) models that relate a material’s thermodynamic variables—specifically pressure, volume/density, energy, and temperature. EOS are typically constructed using semi-empirical parametric methodology, which assumes physics-informed functional form with many tunable parameters calibrated experimental/simulation data. Since there inherent uncertainties in the calibration data (parametric uncertainty) assumed (model...
In a novel experiment that images the momentum distribution of individual, isolated 100-nm-scale plasmas, we make first experimental observation shock waves in nanoplasmas. We demonstrate introduction heating pulse prior to main laser increases intensity wave, producing strong burst quasi-monochromatic ions with an energy spread less than 15%. Numerical hydrodynamic calculations confirm appearance accelerating waves, and provide mechanism for generation control these waves. This distinct...
The equation of state (EOS) materials at warm dense conditions poses significant challenges to both theory and experiment. We report a combined computational, modeling, experimental investigation leveraging new theoretical capabilities investigate warm-dense boron nitride (BN). simulation methodologies include path integral Monte Carlo (PIMC), several density functional (DFT) molecular dynamics methods [plane-wave pseudopotential, Fermi operator expansion (FOE), spectral quadrature (SQ)],...
We have developed an experimental platform at the National Ignition Facility that employs colliding planar shocks to produce warm dense matter with uniform conditions and enable high-precision equation of state measurements. The uses simultaneous x-ray Thomson scattering radiography measure density, electron temperature, ionization in matter. is designed create a large volume plasma (approximately 700×700×150μm3) pressures approaching 100 Mbar minimize distribution volume, significantly...
This manuscript examines the correlations between hot-spot velocity (an observable signature of residual kinetic energy), low-mode implosion asymmetries, and burn amplification in inertial confinement fusion implosions on National Ignition Facility (NIF). Using a combination two-dimensional axis-symmetric three-dimensional radiation-hydrodynamic simulations coupled to neutronics, we find that for typical NIF implosions, stagnation asymmetry multiplies observed anywhere from 80% 120%, while...
In order to understand how close current layered implosions in indirect-drive inertial confinement fusion are ignition, it is necessary measure the level of alpha heating present. To this end, pairs experiments were performed that consisted a low-yield tritium-hydrogen-deuterium (THD) implosion and high-yield deuterium-tritium (DT) validate experimentally simulation-based methods determining yield amplification. The THD capsules designed reduce simultaneously DT neutron (alpha heating)...
A method to study isochoric compression mass densities relevant for direct-drive fast ignition schemes is presented. The based on the combination of one-dimensional radiation-hydrodynamic simulations using code MULTI-IFE [Ramis and Meyer-ter Vehn, Comput. Phys. Commun. 203, 226 (2016)] a particle swarm optimization technique [Kennedy Eberhart, in Proceedings ICNN'95 - International Conference Neural Networks (IEEE, Perth, WA, Australia, 1995), Vol. 4, pp. 1942–1948]. fuel optimized through...
We make direct observations of localized light absorption in a single nanostructure irradiated by strong femtosecond laser field, developing and applying technique that we refer to as plasma explosion imaging. By imaging the photoion momentum distribution resulting from formation laser-irradiated nanostructure, map spatial location highly thereby image nanoscale absorption. Our method probes individual, isolated nanoparticles vacuum, which allows us observe how small variations composition,...