H. W. Herrmann
A5001646843- Laser-Plasma Interactions and Diagnostics
- Nuclear Physics and Applications
- Magnetic confinement fusion research
- Radiation Detection and Scintillator Technologies
- Laser-induced spectroscopy and plasma
- Fusion materials and technologies
- High-pressure geophysics and materials
- Radioactive contamination and transfer
- Cold Fusion and Nuclear Reactions
- Plasma Diagnostics and Applications
- Nuclear reactor physics and engineering
- Atomic and Subatomic Physics Research
- Plasma Applications and Diagnostics
- Particle accelerators and beam dynamics
- Laser-Matter Interactions and Applications
- Laser Design and Applications
- Ionosphere and magnetosphere dynamics
- Atomic and Molecular Physics
- Combustion and Detonation Processes
- Particle Detector Development and Performance
- Nuclear Materials and Properties
- Radioactivity and Radon Measurements
- Electrohydrodynamics and Fluid Dynamics
- Nuclear physics research studies
- Ion-surface interactions and analysis
Los Alamos National Laboratory
2015-2024
Lawrence Livermore National Laboratory
2013-2022
Atomic Weapons Establishment
2008-2021
University of Rochester
2014-2019
Energetics (United States)
2014-2019
ETH Zurich
2009-2019
General Atomics (United States)
1997-2018
Massachusetts Institute of Technology
1997-2018
Indiana University Bloomington
2017-2018
Ohio University
2017-2018
The atmospheric pressure plasma jet (APPJ) [A. Schütze et al., IEEE Trans. Plasma Sci. 26, 1685 (1998)] is a nonthermal, high pressure, uniform glow discharge that produces velocity effluent stream of highly reactive chemical species. operates on feedstock gas (e.g., He/O2/H2O), which flows between an outer, grounded, cylindrical electrode and inner, coaxial powered at 13.56 MHz rf. While passing through the plasma, feedgas becomes excited, dissociated or ionized by electron impact. Once...
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...
The National Ignition Facility (NIF) at Lawrence Livermore Laboratory includes a precision laser system now capable of delivering 1.8 MJ 500 TW 0.35-μm light to target. NIF has been operational since March 2009. A variety experiments have completed in support NIF's mission areas: national security, fundamental science, and inertial fusion energy. capabilities infrastructure are place its missions with nearly 60 X-ray, optical, nuclear diagnostic systems. primary goal the Campaign (NIC) on...
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...
Discharge phenomena of a nonthermal atmospheric pressure plasma source have been studied. An jet (APPJ) operates using rf power and produces stable homogeneous discharge at pressure. After breakdown, the APPJ operation is divided into two regimes, “normal” operating mode when homogeneous, “failure” converts filamentary arc. Current voltage (I–V) characteristics spatially resolved emission intensity profiles measured during normal mode. These measurements show that an alpha (α) capacitive...
An atmospheric pressure plasma source operated by radio frequency power has been developed. This produces a unique discharge that is volumetric and homogeneous at with gas temperature below 300 °C. It also large quantity of oxygen atoms, ∼5×1015 cm−3, which important value for materials applications. A theoretical model shows electron densities 0.2–2×1011 cm−3 characteristic energies 2–4 eV helium discharges level 3–30 W cm−3.
Ignition requires precisely controlled, high convergence implosions to assemble a dense shell of deuterium-tritium (DT) fuel with ρR>∼1 g/cm2 surrounding 10 keV hot spot ρR ∼ 0.3 g/cm2. A working definition ignition has been yield ∼1 MJ. At this the α-particle energy deposited in would have ∼200 kJ, which is already ∼10 × more than kinetic typical implosion. The National Campaign includes low dudded layers study and optimize hydrodynamic assembly diagnostics rich environment. mixture...
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...
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...
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...
Gas breakdown is studied in an atmospheric pressure rf capacitive plasma source developed for materials applications. At a frequency of 13.56 MHz, voltage largely function the product and discharge gap spacing, approximating Paschen curve. However, varies substantially with due to change electron loss mechanism. A large increase observed when argon, oxygen, or nitrogen added helium despite their lower ionization potential. Discussion given optimal conditions at pressure.
Wall conditioning in the Tokamak Fusion Test Reactor (TFTR) [K. M. McGuire et al., Phys. Plasmas 2, 2176 (1995)] by injection of lithium pellets into plasma has resulted large improvements deuterium–tritium fusion power production (up to 10.7 MW), Lawson triple product 1021 m−3 s keV), and energy confinement time 330 ms). The maximum current for access high-performance supershots been increased from 1.9 2.7 MA, leading stable operation at stored values greater than 5 MJ. amount on limiter...
Peak fusion power production of 6.2\ifmmode\pm\else\textpm\fi{}0.4 MW has been achieved in TFTR plasmas heated by deuterium and tritium neutral beams at a total 29.5 MW. These have an inferred central alpha particle density 1.2\ifmmode\times\else\texttimes\fi{}${10}^{17}$ ${\mathrm{m}}^{\mathrm{\ensuremath{-}}3}$ without the appearance either disruptive magnetohydrodynamics events or detectable changes Alfv\'en wave activity. The measured loss rate energetic particles agreed with...
The gamma reaction history (GRH) diagnostic is a multichannel, time-resolved, energy-thresholded γ-ray spectrometer that provides high-bandwidth, direct-measurement of fusion in inertial confinement implosion experiments. 16.75 MeV deuterium+tritium (DT) γ-rays, with branching ratio the order 10(-5)γ/(14 n), are detected to determine fundamental burn parameters, such as nuclear bang time and width, critical achieving ignition at National Ignition Facility. During tritium/hydrogen/deuterium...
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...
High-energy γ rays generated from inertial confinement fusion (ICF) experiments have become an important signature for studying the dynamics of implosion processes. Due to their high-energy and penetrating nature, are most unperturbed products, which can preserve original birth information process. Fusion provide a direct measure nuclear reaction rates (unlike x rays) without being compromised by Doppler spreading neutrons). However, unambiguous γ-ray measurements ICF study further required...
Processing materials at atmospheric pressure provides clear advantages over traditional, vacuum-based plasma processing: in addition to reduction the capital cost of equipment and elimination constraints imposed by vacuum-compatibility, high low temperature processes offer unprecedented improvements for generation active chemical species, selectivity, minimal ion densities resulting surface damage treatment methods unattainable other means. We describe several variations this unique source...
A model for dense packings of disks rolling on each other is presented. This might have application turbulence, tectonic motion, and mechanical gearworks. full classification solutions with fourfold loops given. The fractal dimensions are calculated compare favorably Kolmogoroff scaling turbulence.
After many years of fusion research, the conditions needed for a D–T reactor have been approached on Tokamak Fusion Test Reactor (TFTR) [Fusion Technol. 21, 1324 (1992)]. For first time unique phenomena present in plasma are now being studied laboratory plasma. The magnetic experiments to study plasmas using nearly equal concentrations deuterium and tritium carried out TFTR. At maximum power 10.7 MW, 39.5 MW neutral-beam heating, supershot discharge 6.7 high-βp following current rampdown....
First results from the analysis of neutron image data collected on implosions cryogenically layered deuterium-tritium capsules during 2011-2012 National Ignition Campaign are reported. The span a variety experimental designs aimed at increasing stagnation pressure central hotspot and areal density surrounding fuel assembly. Images neutrons produced by deuterium–tritium fusion reactions in presented, as well images that scatter dense compared with 1D 2D model predictions, consistency checked...
Measurements of the $D(d,p)T$ ($dd$) and $T(t,2n)^{4}\mathrm{He}$ ($tt$) reaction yields have been compared with those $D(t,n)^{4}\mathrm{He}$ ($dt$) yield, using deuterium-tritium gas-filled inertial confinement fusion capsule implosions. In these experiments, carried out on OMEGA laser, absolute spectral measurements $dd$ protons $tt$ neutrons were obtained. From measurements, it was concluded that yield is anomalously low high relative to $dt$ an observation we conjecture be caused by a...
The National Ignition Facility has been used to compress deuterium-tritium an average areal density of ~1.0±0.1 g cm(-2), which is 67% the ignition requirement. These conditions were obtained using 192 laser beams with total energy 1-1.6 MJ and peak power up 420 TW create a hohlraum drive shaped profile, peaking at soft x-ray radiation temperature 275-300 eV. This pulse delivered series shocks that compressed capsule containing cryogenic radius 25-35 μm. Neutron images implosion estimate...
Hydrodynamic mix of the ablator into DT fuel layer and hot spot can be a critical performance limitation in inertial confinement fusion implosions. This results increased radiation loss, cooling spot, reduced neutron yield. To quantify level mix, we have developed simple model that infers contamination using ratio measured x-ray emission to The principal source for “low-foot” class implosions appears been mix. Lower convergence “high-foot” are found less susceptible allowing velocities...