K. Widmann
A5062346760- Laser-induced spectroscopy and plasma
- Laser-Plasma Interactions and Diagnostics
- Atomic and Molecular Physics
- High-pressure geophysics and materials
- X-ray Spectroscopy and Fluorescence Analysis
- Laser-Matter Interactions and Applications
- Mass Spectrometry Techniques and Applications
- Nuclear Physics and Applications
- Laser Design and Applications
- Magnetic confinement fusion research
- Combustion and Detonation Processes
- Advanced Chemical Physics Studies
- Laser Material Processing Techniques
- Ion-surface interactions and analysis
- Plasma Diagnostics and Applications
- Advanced X-ray Imaging Techniques
- Radiation Detection and Scintillator Technologies
- Energetic Materials and Combustion
- Electron and X-Ray Spectroscopy Techniques
- Cold Fusion and Nuclear Reactions
- Particle accelerators and beam dynamics
- Particle Accelerators and Free-Electron Lasers
- Advanced X-ray and CT Imaging
- Calibration and Measurement Techniques
- Diamond and Carbon-based Materials Research
Lawrence Livermore National Laboratory
2016-2025
University Medical Center Utrecht
2025
Atomic Weapons Establishment
2012-2021
General Atomics (United States)
2010-2018
Massachusetts Institute of Technology
2012-2018
International Atomic Energy Agency
2017
Los Alamos National Laboratory
2010-2017
Princeton Plasma Physics Laboratory
2017
University of Nevada, Reno
1995-2017
CEA Cadarache
2017
We present the first collective x-ray scattering measurements of plasmons in solid-density plasmas. The forward spectra a laser-produced narrow-band line from isochorically heated beryllium show that plasmon frequency is sensitive measure electron density. Dynamic structure calculations include collisions and detailed balance match measured spectrum indicating this technique will enable new applications to determine equation state compressibility dense matter.
Indirect-drive hohlraum experiments at the National Ignition Facility have demonstrated symmetric capsule implosions unprecedented laser drive energies of 0.7 megajoule. One hundred and ninety-two simultaneously fired beams heat ignition-emulate hohlraums to radiation temperatures 3.3 million kelvin, compressing 1.8-millimeter-diameter capsules by soft x-rays produced hohlraum. Self-generated plasma optics gratings on either end tune power distribution in hohlraum, which produces a x-ray as...
We report the first direct measurements of total absorption short laser pulses on solid targets in ultrarelativistic regime. The data show an enhanced at intensities above 10(20) W/cm(2), reaching 60% for near-normal incidence and 80%-90% 45 degrees incidence. Two-dimensional particle-in-cell simulations demonstrate that such high is consistent with both interaction preplasma hole boring by intense pulse. A large redshift second harmonic indicates a surface recession velocity 0.035c.
The Hohlraum energetics experimental campaign started in the summer of 2009 on National Ignition Facility (NIF) [E. I. Moses et al., Phys. Plasmas 16, 041006 (2009)]. These experiments showed good coupling laser energy into targets [N. Meezan 17, 056304 (2010)]. They have also demonstrated controlled crossed-beam transfer between beams as an efficient and robust tool to tune implosion symmetry ignition capsules, predicted by earlier calculations [P. Michel Rev. Lett. 102, 025004 A new linear...
The “High-Foot” platform manipulates the laser pulse-shape coming from National Ignition Facility to create an indirect drive 3-shock implosion that is significantly more robust against instability growth involving ablator and also modestly reduces convergence ratio. This strategy gives up on theoretical high-gain in inertial confinement fusion order obtain better control of bring experimental performance in-line with calculated performance, yet keeps absolute capsule relatively high. In...
Measurements have been made of the in-flight dynamics imploding capsules indirectly driven by laser energies 1–1.7 MJ at National Ignition Facility [Miller et al., Nucl. Fusion 44, 228 (2004)]. These experiments were part Campaign [Landen Phys. Plasmas 18, 051002 (2011)] to iteratively optimize inputs required achieve thermonuclear ignition in laboratory. Using gated or streaked hard x-ray radiography, a suite ablator performance parameters, including time-resolved radius, velocity, mass,...
Capsule implosions on the National Ignition Facility (NIF) [Lindl et al., Phys. Plasmas 11, 339 (2004)] are underway with goal of compressing deuterium-tritium (DT) fuel to a sufficiently high areal density (ρR) sustain self-propagating burn wave required for fusion power gain greater than unity. These driven carefully tailored sequence four shock waves that must be timed very precision in order keep DT low adiabat. Initial experiments measure strength and relative timing these shocks have...
The first series of experiments the National Ignition Facility (NIF) [E. I. Moses et al., Phys. Plasmas 16, 041006 (2009)] tested ignition Hohlraum “energetics,” a term described by four broad goals: (1) measurement laser absorption Hohlraum; (2) x-ray radiation flux (TRAD4) on surrogate capsule; (3) quantitative understanding and resultant flux; (4) determining whether initial performance is consistent with requirements for ignition. This paper summarizes status NIF energetics experiments....
A detailed simulation-based model of the June 2011 National Ignition Campaign cryogenic DT experiments is presented. The based on integrated hohlraum-capsule simulations that utilize best available models for hohlraum wall, ablator, and equations state opacities. calculated radiation drive was adjusted by changing input laser power to match experimentally measured shock speeds, merger times, peak implosion velocity, bangtime. crossbeam energy transfer tuned time-dependent symmetry. Mid-mode...
We report on the first layered deuterium-tritium (DT) capsule implosions indirectly driven by a "high-foot" laser pulse that were fielded in depleted uranium hohlraums at National Ignition Facility. Recently, high-foot have demonstrated improved resistance to ablation-front Rayleigh-Taylor instability induced mixing of ablator material into DT hot spot [Hurricane et al., Nature (London) 506, 343 (2014)]. Uranium provide higher albedo and thus an increased drive equivalent additional 25 TW...
Ignition experiments have shown an anomalous susceptibility to hydrodynamic instability growth. To help understand these results, the first growth measurements in indirectly driven implosions on National Facility were performed at ignition conditions with peak radiation temperatures up ∼300 eV. Plastic capsules two-dimensional preimposed, sinusoidal outer surface modulations of initial wavelengths 240 (corresponding a Legendre mode number 30), 120 (mode 60), and 80 μm 90) imploded by using...
We report on record brightness from Ag x-ray emission obtained using a novel laser-produced plasma source. The reported K-shell conversion efficiency of nearly 1% with radiant energy ≈0.6 kJ/sr ions is the highest presently recorded and about twofold greater than more conventional metal-lined cavity targets. He-like are dominant radiators at ≈22.7 keV, which contrast sources other pulse power facilities that produce x-rays Auger processes in near-neutral driven by nonthermal hot electrons...
A measurement of the ${2s}_{1/2}\ensuremath{-}{2p}_{3/2}$ x-ray transition in trapped Li-like ${\mathrm{Bi}}^{80+}$ ions was made that resolved $0.820\ifmmode\pm\else\textpm\fi{}0.026\mathrm{eV}$ hyperfine splitting $({1s}^{2}2s{)}_{F\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}4,5}$ ground configuration, providing first such a multielectron highly charged ion. The intensity ratio two components is shown to be new electron density diagnostic. statistically averaged...
We report the first direct laboratory measurement of spontaneous emission due to hyperfine splitting ground state a highly charged hydrogenlike ion excited by electron collisions. The transition between $F\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}4$ and $F\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}3$ levels $1s^{2}S_{1/2}$ configuration $^{165}H{o}^{65+}$ was observed its wavelength determined $5726.4\ifmmode\pm\else\textpm\fi{}1.5\AA{}$. After taking into account...
Ignition implosions on the National Facility [J. D. Lindl et al., Phys. Plasmas 11, 339 (2004)] are underway with goal of compressing deuterium-tritium fuel to a sufficiently high areal density (ρR) sustain self-propagating burn wave required for fusion power gain greater than unity. These driven very carefully tailored sequence four shock waves that must be timed precision keep entropy and adiabat low ρR high. The first series tuning experiments Facility, which use optical diagnostics...
Indirect drive experiments at the National Ignition Facility are designed to achieve fusion by imploding a fuel capsule with x rays from laser-driven hohlraum. Previous have been unable determine whether deficit in measured ablator implosion velocity relative simulations is due inadequate models of hohlraum or physics. ViewFactor allow for first time direct measure x-ray point view. The show 15%--25% and thus explain nearly all disagreement data. In addition, data this open geometry provide...
Backscattered light via laser-plasma instabilities has been measured in early NIF hohlraum experiments on two beam quads using a suite of detectors. A full aperture backscatter system and near imager (NBI) instrument separately measure the stimulated Brillouin Raman scattered light. Both instruments work conjunction to determine total backscattered power an accuracy ∼15%. In order achieve we have added time-resolution NBI for first time. This capability provides temporally resolved spatial...
Achieving inertial confinement fusion ignition requires a symmetric, high velocity implosion. Experiments show that we can reach 95 ± 5% of the required by using 420 TW, 1.6 MJ laser pulse. In addition, experiments with depleted uranium hohlraum an increase in capsule performance which suggests additional 18 5 μm/ns hohlraums over gold hohlraums. Combining these two would give 99 velocity. have ability to tune symmetry crossbeam transfer. We control second Legendre mode (P2) changing...
Hydrodynamic instabilities are a major obstacle in the quest to achieve ignition as they cause preexisting capsule defects grow and ultimately quench fusion burn experiments at National Ignition Facility. Unstable growth ablation front has been dramatically reduced implosions with ``high-foot'' drives measured using x-ray radiography of modulations most dangerous wavelengths (Legendre mode numbers 30--90). These reductions have helped improve performance layered DT reported by O. A....
A $200\text{ }\text{ }\ensuremath{\mu}\mathrm{m}$ radius hot spot at more than 2 keV temperature, $1\text{ }\mathrm{g}/{\mathrm{cm}}^{3}$ density has been achieved on the National Ignition Facility using a near vacuum hohlraum. The implosion exhibits ideal one-dimensional behavior and 99% laser-to-hohlraum coupling. low opacity of remaining shell bang time allows for measurement x-ray emission reflected central shock in deuterium plasma. Comparison with 1D hydrodynamic simulations puts...
Advances in hohlraums for inertial confinement fusion at the National Ignition Facility (NIF) were made this past year hohlraum efficiency, dynamic shape control, and hot electron x-ray preheat control. Recent experiments are exploring behavior over a large landscape of parameters by changing shape, gas-fill, laser pulse. Radiation hydrodynamic modeling, which uses measured backscatter, shows that gas-filled utilize between 60% 75% power to match bang-time, whereas near-vacuum 98%....
The linear polarization of the 1s2p${\mathrm{}}^{1}$${\mathit{P}}_{1}$\ensuremath{\rightarrow}1${\mathit{s}}^{2}$${\mathrm{}}^{1}$${\mathit{S}}_{0}$ resonance line, 1s2p${\mathrm{}}^{3}$${\mathit{P}}_{1,2}$\ensuremath{\rightarrow}1${\mathit{s}}^{2}$${\mathrm{}}^{1}$${\mathit{S}}_{0}$ intercombination lines, and 1s2s${\mathrm{}}^{3}$${\mathit{S}}_{1}$\ensuremath{\rightarrow}1${\mathit{s}}^{2}$${\mathrm{}}^{1}$${\mathit{S}}_{0}$ forbidden line was measured in heliumlike Fe XXV excited near...