A5054202116- Laser-Plasma Interactions and Diagnostics
- Laser-induced spectroscopy and plasma
- Laser-Matter Interactions and Applications
- Ion-surface interactions and analysis
- Atomic and Molecular Physics
- Laser Design and Applications
- Energetic Materials and Combustion
- Pulsed Power Technology Applications
- Combustion and Detonation Processes
- Magnetic confinement fusion research
- Vacuum and Plasma Arcs
- Plasma Diagnostics and Applications
- Electromagnetic Launch and Propulsion Technology
- Integrated Circuits and Semiconductor Failure Analysis
- Particle accelerators and beam dynamics
- High-pressure geophysics and materials
- Surface Roughness and Optical Measurements
- Electrostatic Discharge in Electronics
- Electrohydrodynamics and Fluid Dynamics
- Diamond and Carbon-based Materials Research
- Magneto-Optical Properties and Applications
- Power Transformer Diagnostics and Insulation
- Laser Material Processing Techniques
- Particle Accelerators and Free-Electron Lasers
- Cold Atom Physics and Bose-Einstein Condensates
RTX (United States)
2012-2020
Defense Systems (United States)
2019
University of Nevada, Reno
1999-2018
University of Rochester
2017-2018
Energetics (United States)
2017-2018
United States Air Force Research Laboratory
2016
n&k Technology (United States)
2002-2010
Sandia National Laboratories
2002-2006
Sandia National Laboratories California
2004
University of Michigan
1998-2003
Using interferometry, we investigate the dynamics of interaction a relativistically intense 4-TW, 400-fs laser pulse with He gas jet. We observe stable plasma channel 1 mm long and less than 30 microm in diameter, radial gradient electron density approximately 5 x 10(22) cm(-4) an on-axis ten times its maximum value 8 10(19) cm(-3). A high velocity surrounding ionization 3.8 10(8) cm/s has been observed after formation, it is attributed to fast ions expelled from propagating radially...
We present observations for 20-MA wire-array z pinches of an extended wire ablation period 57%+/-3% the stagnation time array and non-thin-shell implosion trajectories. These experiments were performed with 20-mm-diam arrays used double- -pinch inertial confinement fusion [M. E. Cuneo, Phys. Rev. Lett. 88, 215004 (2002)] on Z accelerator [R. B. Spielman, Plasmas 5, 2105 (1998)]. This has smallest wire-wire gaps typically at 20 MA (209 microm ). The this indicates that two-dimensional (r-z)...
Experimental and computational investigations of nanosecond electrical explosion a thin Al wire in vacuum are presented. We have demonstrated that increasing the current rate leads to increased energy deposited before voltage collapse. The experimental evidence for synchronization expansion light emission with collapse is Hydrocarbons indicated optical spectra their influence on breakdown physics discussed. radial velocity low-density plasma reaches value approximately 100 km/s. possibility...
An on-axis plasma density depression channel was observed during and after the passage of a relativistically ponderomotively self-guided laser pulse through plasma. Optical interferometry used to produce time-resolved distributions, revealing formation waveguide. These results were complemented by guiding collinear trailing pulse.
Experimental evidence for a strong influence of the radial electric field on energy deposition into thin metal wires during their electrical explosion in vacuum is presented. Explosion wire with positive polarity when "pushes" electrons results twice as much deposited than negative "expels" from wires. Moreover, axial structure changes. This effect can be explained by electronic emission and vapor breakdown along surface.
Experiments show that an expanding metal wire core results from a nanosecond electrical explosion in vacuum consists primarily of three different states: solid, microdrop, and gas-plasma. The state the depends both on amount energy deposited before voltage breakdown heating conditions. For small amounts (on order solid-stage enthalpy), remains solid or is partially disintegrated. high level (more than vaporization energy) gas-plasma state. intermediate melting but less vaporization),...
This paper presents direct experimental proof of a significant increase energy deposition into metal core before voltage breakdown with the current rate for nanosecond exploding wires in vacuum. effect is demonstrated nine different refractory and nonrefractory metals. The strongest influence was tungsten wires. Increasing from 20 to 150 A/ns changes wire solid cluster-like state. For metals such as Ag, Al, Cu, Au, fast explosion allows inside 1.5–2.9 times atomization enthalpy breakdown....
We present the first comprehensive study of high wire-number, wire-array $Z$-pinch dynamics at 14--18 MA using x-ray backlighting and optical shadowgraphy diagnostics. The cylindrical arrays retain slowly expanding, dense wire cores initial position up to 60% total implosion time. Azimuthally correlated instabilities array edge appear during this stage which continue grow in amplitude wavelength after start bulk motion, resulting measurable trailing mass that does not arrive on axis before...
The two- and three-dimensional (2D 3D) versions of ALEGRA-HEDP [A. C. Robinson J. Garasi, “Three-dimensional Z-pinch wire array modeling,” Computer Physics Communications, submitted] have been utilized to simulate discrete effects including precursor formation in 2D (r-θ plane) nonuniform axial ablation (3D). Comparisons made between 3D simulations indicate that overestimate the mass rate by a factor 10–100 with respect case, causing pre-mature motion experimental data. Additionally, case...
The experiments demonstrate the full range of transformations an exploding tungsten wire core from a solid state to total vaporization. These states are correlated with value deposited energy before voltage breakdown. If is less than solid-state enthalpy, remains solid. between solid- and liquid-state disintegrates into macroscopic-sized pieces. breakdown happens during liquid state, expands. In this case, expansion velocity (0.1–1km∕s) almost linear function energy. expanding homogeneous...
The mass distribution and axial instability growth of wire-array Z-pinch implosions driven by 14–20 MA has been studied using high-resolution, monochromatic x-ray backlighting diagnostics. A delayed implosion is consistently observed in which persistent, dense wire cores continuously ablate plasma until they dissipate the main begins. In arrays with small interwire gaps, azimuthally correlated instabilities appear during ablation stage subsequently seed early magneto-Rayleigh–Taylor...
We present experimental evidence of corona-free electrical explosion dielectric-coated W wire in vacuum. A fast current rise approximately 150 A/ns and a coating 2 microm polyimide are both needed to achieve the regime explosion. Breakdown is absent explosion; remains resistive, this allows anomalously high energy deposition (approximately 20 times atomization enthalpy). MHD simulations reproduce main differences between corona explosions. can be useful for generation hot plasma column by...
Experiment demonstrates the first direct transformation of a tungsten wire core to plasma state by Joule heating during nanosecond electrical explosion in vacuum. Energy approximately 130 eV/atom was deposited into 12 microm W coated 2 polyimide 10 ns. All metal rapidly transformed highly ionized plasma, while surrounding coating remained primarily gaseous state. This totally suppressed corona formation. The expansion velocity 12-18 km/s, average ionization at 50 ns reached 67% with...
Nested tungsten wire arrays (20-mm on 12-mm diam.) are shown for the first time to operate in a current-transfer mode at 16-19 MA, even azimuthal interwire gaps of 0.2 mm that smallest typically used any array experiment. After current transfer, inner shows discrete ablation and implosion characteristics identical single array, such as axially nonuniform ablation, delayed acceleration, trailing mass current. The presence from outer may play role determining nested performance.
A method of thermodynamical calculation thin metal wire heating during its electrical explosion is discussed. The technique based on a Joule energy deposition taking into account the current wave form and temperature dependence resistivity heat capacity metal. Comparing to set exploding tungsten experiments demonstrates good agreement up time melting. Good also demonstrated with resistive magnetohydrodynamics simulation. similar for Mo, Ti, Ni, Fe, Al, Cu shows experimental data. useful...
Measurements within 10% accuracy of the dynamic dipole polarizabilities $\ensuremath{\alpha}(\ensuremath{\lambda})$ for five nonrefractory metal atoms (Mg, Ag, Al, Cu, and Au) at laser wavelengths $\ensuremath{\lambda}=532$ $1064\phantom{\rule{0.3em}{0ex}}\mathrm{nm}$ are presented using electrical explosion thin wires in vacuum a novel probing integrated-phase technique. The technique is based on single-wavelength interferometry does not require axial symmetry tested object. Theoretical...
We are studying the behavior of self-breaking, high-voltage water switches for Z refurbishment project. In Z-20, three or four in parallel charged to 4 MV /spl sim/220 ns. The gap between switch electrodes is 13-15 cm, and enhancement positive negative varied study time-evolution breakdown arcs, current sharing, simultaneity. addition standard electrical diagnostics (V,I), we looking at one more during phase with two optical diagnostics: a streak camera fast framing camera. has sim/1-ns...
The dynamics of mass transport were observed in a wire array implosion with multiframe laser probing. Plasma bubbles arise at breaks the wires. Interferometry shows that leading edge brings material to axis array. speed this was measured be > or =3 x 10(7) cm/s during implosion. A shock collision precursor. Faraday effect indicates current flowing on switches from imploding on-axis plasma column beginning x-ray pulse.
Using a two-frame intensified charge coupled device (iCCD) imaging system with 2 ns exposure time, we observed the dynamics of voltage breakdown and corona generation in experiments fast ns-time exploding fine Ni stainless-steel (SS) wires vacuum. These show that along wire surface is subjected to temporal-spatial inhomogeneity. For both metal wires, an initial bright cathode spot before ionization entire length. This does not expand time. 25.4 μm diameter SS explosions positive polarity,...
A Faraday rotation diagnostic was applied for the investigation of magnetic fields in plasma 1-MA wire arrays and X-pinches. Laser-probing diagnostics at Zebra generator include a four-channel polarointerferometer four-frame shadowgraphy. The consists shadow channels, shearing air-wedge interferometer, an additional schlieren channel. implosion dynamics were studied. current column Al low-wire number found by diagnostic. Optical showed turbulent bubblelike objects arrays. demonstrated...
Progress in understanding the physics of dynamic-hohlraums is reviewed for a system capable generating 13 TW axial radiation high temperature (>200 eV) radiation-flow experiments and ICF capsule implosions.
Experiments with electrically exploding fine Al and Ag wires in air demonstrate a strong dependence of the expanding metal core condition velocity on ambient pressure. Expansion wire varies by 23 times between ∼0.2 km/s ∼4.6 km/s. The shock-wave at atmospheric pressure is ∼5 increases to ∼6 when decreased 50 Torr. strongly dependent material whether it into vacuum or against for different surrounding pressures general agree Paschen's Law gap.
Laser shadowgrams of exploding metal wires in a vacuum show the anomalous transparency completely evaporated wire core for probe beam with wavelength 1064 nm. Simultaneous at 532 nm significant light attenuation. The laser radiation is highly likely due to Rayleigh scattering probing by atoms. Our experimental results can be explained under assumption strongly non-equilibrium state an expanding gas cylinder non-uniform density.
Electrical breakdown simulations for liquids, in response to a submicrosecond (~100-200 ns) voltage pulse, are carried out. It is shown that initiated by field emission at the interface of preexisting microbubbles. Impact ionization within microbubble gas then contributes plasma development, with cathode injection having delayed and secondary role. The model used this paper adequately explains experimentally observations prebreakdown current fluctuations, streamer propagation branching, as...