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in subjects: "Ablation"

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RIMS diagnostics for laser desorption/laser ablation

Laser desorption mass spectrometry is a useful method for interrogating materials and events at or near surfaces. Laser desorption/ablation combined with Resonance Ionization Mass Spectrometry (RIMS) provides a powerful tool to obtain information on chemical composition and speciation and, in some cases, internal and translational energy distributions. The application of this technique to the interrogation of materials and interfaces is discussed for several systems, including the analysis of c… more

Date: January 1, 1986

Creator: Apel, E. C.; Nogar, N. S.; Miller, C. M. & Estler, R. C.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Results of hydrogen pellet injection into ISX-B

High speed pellet fueling experiments have been performed on the ISX-B device in a new regime characterized by large global density rise in both ohmic and neutral beam heated discharges. Hydrogen pellets of 1 mm in diameter were injected in the plasma midplane at velocities exceeding 1 km/s. In low temperature ohmic discharges, pellets penetrate beyond the magnetic axis, and in such cases a sharp decrease in ablation is observed as the pellet passes the plasma center. Density increases of appro… more

Date: September 1, 1980

Creator: Milora, S. L.; Foster, C. A. & Thomas, C. E.

Item Type: Report

Partner: UNT Libraries Government Documents Department

open access

Why plasma armature railguns don't work (and what can be done about it)

Plasma armature railguns have failed to achieve the high velocities predicted in the early 1980's. Only a few experiments in the last decade have exceeded the velocity of 5.9 km/s obtained by Rashleigh and Marshall in their pioneering plasma armature experiments. The apparent barrier at 6 to 7 km/s results from viscous and ablation drag on neutral and ionized material in the railgun bore. It has taken almost five years to understand and demonstrate clearly the inter-relation of ablation, viscou… more

Date: January 1, 1988

Creator: Parker, J. V.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Calculation of density profiles in tandem mirrors fueled by pellets

We have modified the LLNL radial transport code TMT to model reactor regime plasmas, fueled by pellets. The source profiles arising from pellet fueling are obtained from existing pellet ablation models. Because inward radial diffusion due to inverted profiles must compete with trapping of central cell ions in the transition region for tandem mirrors, pellets must penetrate fairly far into the plasma. In fact, based on our radial calculations, a pellet with a velocity of 10 km/sec cannot sustain… more

Date: December 2, 1983

Creator: Campbell, R. B. & Gilmore, J. M.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Space nuclear safety program. Progress report, August 1983

This technical monthly report covers studies related to the use of /sup 238/PuO/sub 2/ in radioisotope power systems carried out for the Office of Special Nuclear Projects of the US Department of Energy by Los Alamos National Laboratory. Most of the studies discussed here are ongoing. Results and conclusions described may change as the work continues.

Date: January 1, 1984

Creator: Bronisz, S. E.

Item Type: Report

Partner: UNT Libraries Government Documents Department

open access

Space Nuclear Safety Program. Progress report

Date: January 1, 1984

Creator: Bronisz, S. E.

Item Type: Report

Partner: UNT Libraries Government Documents Department

open access

Highly ionized plasma plume generation by long-pulse CO/sub 2/ laser irradiation of solid targets in strong axial magnetic fields

The present work utilizes high f number optics and is directed primarily at controlling the conditions in the magnetically confined plume. Typically, fully ionized carbon plasmas have been produced with 10/sup 18/ cm/sup -3/ electron densities and 100 to 150 eV electron temperatures. These carbon plasmas have been doped with high Z atoms in order to study ionization and emission rates at the above conditions.

Date: January 1, 1982

Creator: Hoffman, A L & Crawford, E A

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Uniform laser ablative acceleration of targets at 10/sup 14/ W/cm/sup 2/

We present the first detailed investigations of the ablative acceleration of planar targets while simultaneously using high irradiance (10/sup 14/ W/cm/sup 2/), large focal diameters (1 mm) and long laser pulse duration (3 nsec). Included are measurements of target preheat, ablation pressures and uniformity achieved under these conditions. Targets were accelerated to high velocities with velocity profile uniformity approaching that required for high gain pellet implosions.

Date: August 10, 1982

Creator: Obenschain, S. P.; Whitlock, R. R.; McLean, E. A.; Ripin, B. H.; Price, R. H.; Phillion, D. W. et al.

Item Type: Report

Partner: UNT Libraries Government Documents Department

open access

Improved understanding of first-mall vaporization-condensation in inertial confinement fusion reactors. Revision 1

We report approximate x-ray and debris spectra emanating from a region of compressed DT fuel representing the imploded configuration of a generic direct-drive ICF reactor pellet. We show how the spectra are modified by spherical lead shields of various thicknesses placed near the pellet, and show that it is not possible to lessen the ablation of the first wall or blanket of a low-pressure ICF reactor chamber through use of such shields. Then we report that the calculated x-ray spectra alone (i.… more

Date: August 1, 1986

Creator: Orth, C.D.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Heat transfer modelling of first walls subject to plasma disruption

A brief description of the plasma disruption problem and potential thermal consequences to the first wall is given. Thermal models reviewed include: a) melting of a solid with melt layer in place; b) melting of a solid with complete removal of melt (ablation); c) melting/vaporization of a solid; and d) vaporization of a solid but no phase change affecting the temperature profile.

Date: January 1, 1981

Creator: Fillo, J.A. & Makowitz, H.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

The SRS (Segmented Rail Surface) railgun: A new approach to restrike control. [Segmented rail surface]

A Segmented Rail Surface (SRS) structure is described that eliminates restrike arcs by progressively disconnecting segments of the rail surface after the plasma armature has passed. This technique has been demonstrated using the Los Alamos MIDI-2 railgun. Restrike was eliminated in a plasma armature acceleration experiment using metal-foil fuses as opening switches. A plasma velocity increase from 11 to 16 km/s was demonstrated using the SRS technique to eliminate the viscous drag losses associ… more

Date: January 1, 1988

Creator: J.V., Parker

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Streaked x-ray microscopy of laser-fusion targets

An ultrafast soft x-ray streak camera has been coupled to a Wolter axisymmetric x-ray microscope. This system was used to observe the dynamics of laser fusion targets both in self emission and backlit by laser produced x-ray sources. Spatial resolution was 7 ..mu..m and temporal resolution was 20 ps. Data is presented showing the ablative acceleration of foils to velocities near 10/sup 7/ cm/sec and the collision of an accelerated foil with a second foil, observed using 3 keV streaked x-ray bac… more

Date: August 1, 1982

Creator: Price, R. H.; Campbell, E. M.; Rosen, M. D.; Auerbach, J. M.; Phillion, D. W.; Whitlock, R. R. et al.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Investigation of multi-layer thin films for energy storage.

We investigate here the feasibility of increasing the energy density of thin-film capacitors by construction of a multi-layer capacitor device through ablation and redeposition of the capacitor materials using a high-power pulsed ion beam. The deposition experiments were conducted on the RHEPP-1 facility at Sandia National Laboratories. The dielectric capacitor filler material was a composition of Lead-Lanthanum-Zirconium-Titanium oxide (PLZT). The energy storage can be increased by using mater… more

Date: January 1, 2009

Creator: Renk, Timothy Jerome & Monson, Todd

Item Type: Report

Partner: UNT Libraries Government Documents Department

open access

Structural transformations in Sc/Si multilayers irradiated by EUVlasers

Multilayer mirrors for the extreme ultraviolet (EUV) are keyelements for numerous applications of coherent EUV sources such as newtabletop lasers and free-electron lasers. However the field ofapplications is limited by the radiation and thermal stability of themultilayers. Taking into account the growing power of EUV sources thestability of the optics becomes crucial. To overcome this problem it isnecessary to study the degradation of multilayers and try to increasetheir temporal and thermal st… more

Date: August 21, 2007

Creator: Voronov, D. L.; Zubarev, E. N.; Pershyn, Y. P.; Sevryukova, V. A.; Kondratenko, V. V.; Vinogradov, A. V. et al.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Ultra-fast Laser Synthesis of Nanopore Arrays in Silicon for Bio-molecule Separation and Detection

We demonstrate that interference of ultra-fast pulses of laser light can create regular patterns in thin silicon membranes that are compatible with the formation of a uniform array of nanopores. The spacing and size of these pores can be tuned by changing the laser energy, wavelength and number of ultra-short pulses. Short pulses and wavelengths ({approx}550 nm and smaller) are needed to define controllable nanoscale features in silicon. Energy must be localized in time and space to produce the… more

Date: February 7, 2008

Creator: Tringe, J. W.; Ileri, N.; Letant, S. E.; Stroeve, P.; Shirk, M.; Zaidi, S. et al.

Item Type: Report

Partner: UNT Libraries Government Documents Department

open access

Multi-Megajoule NIF: Ushering In a New Era in High Energy Density Science

This paper describes the status of the stadium-sized National Ignition Facility (NIF), the world's largest laser system and first operational multi-megajoule laser. The 192-beam NIF, located at Lawrence Livermore National Laboratory (LLNL), is 96% complete and scheduled for completion in March 2009. The NIF laser will produce nanosecond laser pulses with energies up to approximately 4 MJ in the infrared (laser wavelength = 1.053-{micro}m) and 2MJ in the ultraviolet (laser wavelength = 0.35-{mic… more

Date: April 30, 2008

Creator: Keane, C & Moses, E I

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

An analysis of molten-corium-induced failure of drain pipes in BWR Mark 2 containments

This study has focused on mechanistic simulation and analysis of potential failure modes for inpedestal drywell drain pipes in the Limerick boiling water reactor (BWR) Mark 2 containment. Physical phenomena related to surface tension breakdown, heatup, melting, ablation, crust formation and failure, and core material relocation into drain pipes with simultaneous melting of pipe walls were modeled and analyzed. The results of analysis have been used to assess the possibility of drain pipe failur… more

Date: January 1, 1991

Creator: Taleyarkhan, R. P. & Podowski, M. Z.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Ablation of material by front surface spallation

Laser irradiation can be utilized to remove (i.e., ablate) material in a controlled manner by a hydrodynamic process, referred to as front surface spallation. In this process, a thin layer next to a free surface is heated to a level (below vaporization) so rapidly that it cannot undergo thermal expansion during laser heating. This generates a stress pulse, which propagates both inward and toward the free surface, with an initial amplitude that can be calculated using the Grueneisen coefficient.… more

Date: January 1, 1991

Creator: Dingus, R. S. & Scammon, R. J.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Plutonium release from pressed plutonium oxide fuel pellets in aquatic environments

Plutonium oxide pellets (80% /sup 238/Pu, 40 g each) were exposed to fresh water and sea water at two temperatures for 3 y in enclosed glass chambers. The concentrations of plutonium observed in the waters increased linearly with time throughout the experiment. However, the observed release rates were inversely dependent on temperature and salinity, ranging from 160 ..mu..Ci/day for cold fresh water to 1.4 ..mu..Ci/day for warm sea water. The total releases, including the chamber residues, show… more

Date: December 1, 1983

Creator: Patterson, J. H.; Steinkruger, F. J.; Matlack, G. M.; Heaton, R. C.; Coffelt, K. P. & Herrera, B.

Item Type: Report

Partner: UNT Libraries Government Documents Department

open access

Wavelength scaling of implosion symmetry, ablation pressure, and hydrodynamic efficiency in laser fusion

We examine the scaling of implosion symmetry, ablation pressure, and hydrodynamic efficiency with the wavelength of the laser, using a recent theoretical analysis of ablative laser driven implosions as a tool. Symmetrization by a hot atmosphere is most effective for long wavelength lasers, whereas ablation pressure and hydrodynamic efficiency are best for shorter laser wavelengths.

Date: July 31, 1981

Creator: Max, C.E.; Lindl, J.D. & Mead, W.C.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Laser ablation mass spectrometry of levitated microparticles

No Description Available.

Date: January 1, 1991

Creator: Dale, J. M.; Whitten, W. B. & Ramsey, J. M.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Simple spherical ablative-implosion model

A simple model of the ablative implosion of a high-aspect-ratio (shell radius to shell thickness ratio) spherical shell is described. The model is similar in spirit to Rosenbluth's snowplow model. The scaling of the implosion time was determined in terms of the ablation pressure and the shell parameters such as diameter, wall thickness, and shell density, and compared these to complete hydrodynamic code calculations. The energy transfer efficiency from ablation pressure to shell implosion kinet… more

Date: June 23, 1980

Creator: Mayer, F. J.; Steele, J. T. & Larsen, J. T.

Item Type: Report

Partner: UNT Libraries Government Documents Department

open access

Annual dynamics within the active layer

We have continued our meteorological and hydrologic data collection in support of our process-oriented research. The six years of data collected to date is unique in its scope and continuity in a North Hemisphere Arctic setting. This valuable data base has allowed us to further our understanding of the interconnections and interactions between the atmosphere/hydrosphere/biosphere/lithosphere. The increased understanding of the heat and mass transfer processes has allowed us to increase our mode… more

Date: January 1, 1991

Item Type: Report

Partner: UNT Libraries Government Documents Department

open access

Space nuclear safety program. Progress report, July 1983

Date: November 1, 1983

Creator: Bronisz, S. E.

Item Type: Report

Partner: UNT Libraries Government Documents Department