A5029747880- Atomic and Molecular Physics
- Laser-Plasma Interactions and Diagnostics
- Laser-induced spectroscopy and plasma
- Plasma Diagnostics and Applications
- X-ray Spectroscopy and Fluorescence Analysis
- Ion-surface interactions and analysis
- Advanced Chemical Physics Studies
- Laser Design and Applications
- Combustion and Detonation Processes
- Nuclear Physics and Applications
- Mass Spectrometry Techniques and Applications
- Magnetic confinement fusion research
- Pulsed Power Technology Applications
- Laser-Matter Interactions and Applications
- Gas Dynamics and Kinetic Theory
- Ionosphere and magnetosphere dynamics
- Electron and X-Ray Spectroscopy Techniques
- Energetic Materials and Combustion
- Electrostatic Discharge in Electronics
- Particle accelerators and beam dynamics
- Advanced X-ray Imaging Techniques
- Particle Accelerators and Free-Electron Lasers
- Integrated Circuits and Semiconductor Failure Analysis
- Metal and Thin Film Mechanics
- Astro and Planetary Science
United States Naval Research Laboratory
2014-2024
United States Navy
2023
Sandia National Laboratories
2014-2022
Engility (United States)
2014
LightMachinery (Canada)
2010
Bharat Heavy Electricals (India)
1997-2010
Naval Research Laboratory Plasma Physics Division
1990-2007
Goddard Space Flight Center
1984-1985
National Aeronautics and Space Administration
1984-1985
Pulsed power accelerators compress electrical energy in space and time to provide versatile experimental platforms for high density inertial confinement fusion science. The 80-TW “Z” pulsed facility at Sandia National Laboratories is the largest device world today. Z discharges up 22 MJ of stored its capacitor banks into a current pulse that rises 100 ns peaks as 30 MA low-inductance cylindrical targets. Considerable progress has been made over past 15 years use precision scientific tool....
Electron-impact excitation of $\mathrm{Ar}\mathrm{}\mathrm{I}$ from the ground ${3p}^{6}{}^{1}{S}_{0}$ as well two metastable levels ${3p}^{5}4s$ ${(}^{3}{P}_{2}$ and ${}^{3}{P}_{0})$ configuration to all ten ${3p}^{5}4p$ excited are calculated in distorted-wave approximation. Polarization state is explicitly included by adding a polarization potential calculation. Unitarization scattering matrix $\mathbf{S}$ carried out including elastic terms, effects unitarization $\mathrm{LS}$...
The scattering of electrons from argon atoms is studied by the method polarized orbitals. 3p\ensuremath{\rightarrow}d perturbed orbital calculated using Sternheimer approximation gives polarizability 14.29${a}_{0}^{3}$. perturbation orbitals 1s, 2s, 2p, and 3s taken into account renormalizing to give experimental value 11.06${a}_{0}^{3}$. Using only modified in total wave function, phase shifts for various partial waves have been exchange, exchange-adiabatic, polarized-orbital...
Imploding wire arrays on the 20 MA Z generator have recently provided some of most powerful and energetic laboratory sources multi-keV photons, including ∼375 kJ Al K-shell emission (hν ∼ 1–2 keV), ∼80 stainless steel 5–9 keV) a kJ-level Mo 17 keV). While global implosion dynamics these different are very similar, physical process that dominates from x-ray fall into three broad categories. produce column plasma with densities up to ∼3 × 1021 ions/cm3, where opacity inhibits escape photons....
A comprehensive gas puff capability is being developed on the Z pulsed power generator. We describe methodology employed for developing a load Z, which combines characterization and modeling of neutral mass flow from supersonic nozzle, numerical implosion this profile, experimental evaluation these magnetic implosions Z. are beginning multiyear science program to study z-pinch physics at high current, starting with an 8-cm diameter double-shell delivers column Ar that imploded by machine's...
The dynamics of Xe clusters with initial radius between 10 and 100 Å irradiated by an IR subpicosecond laser pulse is investigated. evolution the cluster modeled a relativistic time-dependent three-dimensional particle simulation model. focus this investigation to understand energy absorption how absorbed distributed among various degrees freedom. consequence on energy, average charge per atom, mean electron ion energies, ionization, removal electrons from cluster, expansion was studied....
Nested stainless steel wire array variations were investigated on the 20MA Z machine [R. B. Spielman et al., Phys. Plasmas 5, 2105 (1998)]. In order to reach experimentally observed electron temperatures near 3.8keV and excite K shell, these ∼6.7keV photon energy x-ray sources must be of large initial diameter (45–80mm) which poses a concern for magnetic Rayleigh–Taylor instability growth. We discuss implosion dynamics in arrays, including an analysis ablation phase indicating that prefill...
Argon gas puffs have produced 330 kJ ± 9% of x-ray radiation above 3 keV photon energy in fast z-pinch implosions, with remarkably reproducible K-shell spectra and power pulses. This reproducibility production is particularly significant light the variations instability evolution observed between experiments. Soft measurements line ratios from a time-resolved spectrum at peak suggest that plasma gradients these high-mass pinches may limit radiating mass, power, yield high-current puffs.
The electron deposition in an Ar–Kr–F2 mixture, based on a solution of the Boltzmann equation, is presented. model relevant to electron-beam generated KrF* laser amplifier at atmospheric pressure. Sets cross sections for Ar, Kr, and F2 have been compiled. Calculations performed determine energy distribution function, per electron–ion pair ionization excitation rates. It found that inclusion inner shell subsequent Auger emission are essential matching known results both Wei stopping power...
A relativistic time-dependent three-dimensional particle simulation model has been developed to study the interaction of intense ultrashort KrF laser pulses with small Xe clusters. The trajectories electrons and ions are treated classically according equation motion. applied a different regime ultrahigh intensities extending . In particular, behavior clusters from sufficient for transition so-called ``collective oscillation model'' explored. At peak below , all removed cluster form plasma....
Scattering of electrons from neon atoms is investigated by the polarized-orbital method. The perturbed orbitals calculated with use Sternheimer approximation lead to polarizability $2.803{a}_{0}^{3}$, in fairly good agreement experimental value $2.66{a}_{0}^{3}$. Phase shifts for various partial waves are exchange, exchange-adiabatic, and approximations. They compared previous results. elastic differential, total, momentum-transfer cross sections polarizedorbital yields results which show...
The difference between the ion thermal and effective temperatures is investigated through simulations of Ne gas puff z-pinch reported by Kroupp et al. [Phys. Rev. Lett. 107, 105001 (2011)]. Calculations are performed using a 2D, radiation-magnetohydrodynamic code with Tabular Collisional-Radiative Equilibrium, namely Mach2-TCRE [Thornhill al., Phys. Plasmas 8, 3480 (2001)]. extensive data set imaging K-shell spectroscopy from experiments provides challenging validation test for simulations....
Recent experiments on the Z accelerator have produced high-energy (17 keV) inner-shell K-alpha emission from molybdenum wire array z-pinches. Extensive absolute power and spectroscopic diagnostics along with collisional-radiative modeling enable detailed investigation into roles of thermal, hot electron, fluorescence processes in production x-rays. We show that changing dimensions arrays can impact proportion thermal non-thermal K-shell
We present collisional-radiative-equilibrium (CRE) gain calculations for the important J=2-1 and J=0-1 3p-3s transitions of neonlike selenium using an extensive set accurate excited-state couplings self-consistently calculated ionization abundances. An atomic model was put together containing all most significant processes impacting calculation these in order to determine sensitivity ratio lines monopole excitation cross sections CRE. It is seen that variations a factor 2 or 3 are needed...
Theoretical results from multistate semirelativistic Breit-Pauli R-matrix calculations and two first-order distorted-wave are presented for electron-impact excitation of krypton the ${(4p}^{5}5s)$ $J=0,2$ metastable states to ${(4p}^{5}5p)$ manifolds. Except a few cases, in which method account relativistic effects becomes surprisingly critical, fair overall agreement between predictions various theoretical models is achieved intermediate high energies. However, significant discrepancies...
We review spectroscopic methods developed for the determination of magnetic fields in high-energy-density (HED) plasmas. In such plasmas, common Zeeman-splitting magnetic-field diagnostics are often impeded by various broadening mechanisms atomic transitions. The described, encompassing transitions visible and ultraviolet spectral regions, applied to study imploding plasmas (in a Z-pinch configuration) with without pre-embedded fields, relativistic-electron focusing diodes, plasma-opening...
The influence of intense picosecond heating and time-dependent ionization on the population dynamics Ne-like selenium is investigated. We find that highly nonequilibrium plasma conditions a large gain coefficient >500 ${\mathrm{cm}}^{\mathrm{\ensuremath{-}}1}$ can be generated for J=0--1 line at 182 \AA{} KrF laser intensities >3\ifmmode\times\else\texttimes\fi{}${10}^{16}$ W/${\mathrm{cm}}^{2}$. Thus, observation x-ray lasing or near critical surface short-pulse, heated appears...
The atomic xenon laser is among the most efficient and powerful of near-infrared gas lasers, especially when pumped by molecular ions in an $\mathrm{Ar}\text{\ensuremath{-}}\mathrm{Xe}$ mixture. Accurate transition probabilities for transitions are critical developing a fundamental understanding inversion dynamics, gain, power extraction this device. We compare results from several methods calculating six lines ranging wavelength $1.733$ to...
The Ar–Xe infrared laser has been investigated in several series of experiments carried out on the Naval Research Laboratory’s Electra generator. Our primary goals were to optimize efficiency (within Electra’s capabilities) and gain understanding main physical processes underlying laser’s output as a function controllable parameters such Xe fraction, power deposition, gas pressure. We find that intrinsic maximizes at ∼3% total pressure 2.5 atm, fraction 1%, electron beam deposition density...
Electron-impact excitation of the ${4p}^{5}5s$ and ${4p}^{5}5p$ levels Kr I has been investigated in detail by calculating cross sections using distorted-wave close-coupling approaches. The results are presented from thresholds up to 50 eV incident energy. They contrasted among different calculations compared with other theoretical predictions experimental data. Significant disagreement is found many recent data Chilton et al. [Phys. Rev. A 62, 032714 (2000)].
Calculations for electron deposition in beam generated KrF laser at atmospheric pressure have been performed. The impact of the Ar/Kr/F2 gas mixture on energy distribution function, density, and mean energy, per electron–ion pair, attachment, dissociation, excitation, ionization rates investigated. F2 abundance controls low (≲9 eV) component while both fluorine krypton mole fraction affect midenergy domain (9 to ∼25 eV). Consequently, attachment rate coefficient varies with (xF2) such that...