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in subjects: "Ablation"

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Feasibility Study of Microsecond Pulsed Microwave Ablation Using a Minimally Invasive Antenna

Article establishing the feasibility of producing localized ablation zones using microsecond pulsed microwave ablation (MWA) as an alternative to conventional continuous wave (CW) MWA. Results open the opportunity for developing a coupled MWA treatment and imaging system using pulsed MWA and microwave-induced thermoacoustic signals for real-time monitoring of MWA.

Date: February 16, 2021

Creator: Evans, Audrey L.; Sawicki, James F.; Luyen, Hung; Mohtashami, Yahya; Behdad, Nader & Hagness, Susan C.

Item Type: Article

Partner: UNT College of Engineering

open access

Facies of ion bombarded surfaces of brittle materials. [Protons, deuterons, He ions]

Materials were bombarded by protons, deuterons, and helium ions. The materials investigated were quartz; glasses; carbides and borides (SiC, B/sub 4/C, TiB/sub 2/); oxides and nitrides (magnorite, sapphire, spinel, Al/sub 2/O/sub 3/, Si/sub 3/N/sub 4/, ZrO/sub 2/, BaTiO/sub 3/); and miscellaneous (graphite, LiNbO/sub 3/, copper). Oberservations were of growth, reflectivity, blistering, surface ablation, and swelling. Calculations were made of the effects of a layer, of its gradual transformatio… more

Date: December 1, 1975

Creator: Primak, W.

Item Type: Report

Partner: UNT Libraries Government Documents Department

open access

Preliminary model for core/concrete interactions. [PWR and BWR]

A preliminary model is described for computing the rate of penetration of concrete by a molten LWR core. Among the phenomena included are convective stirring of the melt by evolved gases, admixture of concrete decomposition products to the melt, chemical reactions, radiative heat loss, and variation of heat transfer coefficients with local pressure. The model is most applicable to a two-phase melt (metallic plus oxidic) having a fairly high metallic content.

Date: August 1, 1977

Creator: Murfin, W. B.

Item Type: Report

Partner: UNT Libraries Government Documents Department

open access

2-MW plasmajet facility thermal tests of concrete. [PWR and BWR]

A test was made in the 2-Megawatt Plasmajet Facility to obtain experimental data relative to the thermal response of concrete to incident heat flux. 14.6 cm diameter by 8.0 cm long concrete cylinders were positioned in a supersonic flow of heated nitrogen from an arc heater. The end of the concrete cylinders impacted by the flow were subjected to heat fluxes in the range of 0.13 to 0.35 kW/cm/sup 2/. Measurements included cold wall surface heat flux and pressure distributions, surface and indep… more

Date: July 1, 1977

Creator: Goin, Kenneth L.

Item Type: Report

Partner: UNT Libraries Government Documents Department

open access

ORNL neutral gas shielding model for pellet-plasma interactions

A revised neutral molecule ablation model is derived to describe the evaporation of a solid hydrogen pellet in a tokamak plasma. The approach taken is based on the theory of Parks, Turnbull, and Foster who postulate that a cloud of molecular hydrogen surrounding the pellet shields the surface from incoming energetic electrons and, in so doing, regulates the evaporation rate. This treatment differs from an earlier model in that the hydrodynamic behavior of the molecular cloud is treated in a sel… more

Date: May 1, 1977

Creator: Milora, S. L & Foster, C. A.

Item Type: Report

Partner: UNT Libraries Government Documents Department

open access

Symmetry and illumination uniformity requirements for high density laser-driven implosions

As laser capabilities increase, implosions will be performed to achieve high densities. Criteria are discussed for formation of a low-density corona, preheated supersonically, which increases the tolerance of high convergence implosions to non-uniform illumination by utilizing thermal smoothing. We compare optimized double shell target designs without and with atmosphere production. Two significant penalties are incurred with atmosphere production using 1 ..mu..m laser light. First, a large ini… more

Date: October 22, 1976

Creator: Mead, W. C. & Lindl, J. D.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Commercial application of laser fusion

The fundamentals of laser-induced fusion, some laser-fusion reactor concepts, and attendant means of utilizing the thermonuclear energy for commercial electric power generation are discussed. Theoretical fusion-pellet microexplosion energy release characteristics are described and the effects of pellet design options on pellet-microexplosion characteristics are discussed. The results of analyses to assess the engineering feasibility of reactor cavities for which protection of cavity components … more

Date: January 1, 1976

Creator: Booth, L. A.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Effects of density gradient modification on fluid instability in thermonuclear micro-implosions

The presence of hydrodynamic fluid instability at the ablation surface puts constraints on the kinds of targets, surface finish, and energy sources that one can use for thermonuclear micro-implosions. If Taylor-like modes grow at near the classical value, one is limited to low aspect ratio shells and surface finishes of 10-100 A. These surface finish requirements can be reduced by 1 to 2 orders of magnitude by exploiting density gradient modification techniques to obtain a shallow density gradi… more

Date: September 24, 1976

Creator: Lindl, J. D.; Bangerter, R. O.; Nuckolls, J. H.; Mead, W. C. & Thomson, J. J.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Plasma flows in the conduction region of a spherical laser target

Analytic solutions are dervied for plasma flows in a spherical laser target, emphasizing the region which lies between the ablation surface and the critical density surface. Electron thermal conductivity dominates the heat transport in this zone. Both classical electron thermal conduction and flux-limited conduction are treated in which the finite electron thermal velocity provides an upper bound to the heat flux. These analytic solutions are compared with computational results from 1-D hydrody… more

Date: October 21, 1976

Creator: Max, C. E.; McKee, C. F. & Mead, W. C.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Some effects of laser irradiation on aluminum

Ten samples of aluminum were irradiated by a 1.06-..mu..m mode-locked laser (25 ps) to various energy levels. The excavations were examined by optical and scanning electron microscopy. Rough computations of the mass of metal removed indicated a relationship of energy of the laser shot to the mass removed as about 9 J/mole. In some cases there is good evidence to indicate compression of the metal, but no values for this compression could be obtained.

Date: December 1, 1975

Creator: Hoffman, C. G.

Item Type: Report

Partner: UNT Libraries Government Documents Department

open access

Roll torque evaluation (RTE) vehicle postflight test report. [Spin effect of tape wrapped heat shield]

Results of analyses of the roll torque evaluation (RTE) vehicle, a reentry configuration which was flight-tested during May 1974 at the Sandia Laboratories Tonopah Test Range are presented. The purpose of the test program was to evaluate, in a controlled environment, the roll-torque-producing effect of an ablating tape-wrapped carbon phenolic (TWCP) heat shield. The boost system, a Talos-Terrier-Recruit (TATER) rocket, delivered the reentry configuration to conditions approximating the latter p… more

Date: March 1, 1976

Creator: Kryvoruka, J. K.

Item Type: Report

Partner: UNT Libraries Government Documents Department

open access

Experimental screening of carbon-base materials for impact members in isotopic heat sources

Fourteen C/C composites and three reentry-grade bulk graphites were evaluated experimentally to determine their applicability for impact member use in radioisotope heat sources. The composites included the following generic types: (1) 2-D cloth lay-ups; (2) 2-D and 3-D felts; (3) 3-D weaves; (4) 3-D pierced fabrics; (5) 7-D weave; and (6) coarse polar weave. Also included was the 2-D randomly wound, resin-impregnated C/C material presently used as the impact member in the MHW RTG and commonly d… more

Date: November 1, 1976

Creator: Bansal, G. K. & Duckworth, W. H.

Item Type: Report

Partner: UNT Libraries Government Documents Department

open access

Laser-driven ICF experiments: Laboratory Report No. 223

Laser irradiation uniformity is a key issue and is treated in some detail. The basic irradiation uniformity requirements and practical ways of achieving these requirements are both discussed, along with two beam-smoothing techniques: induced spatial incoherence (ISI), and smoothing by spectral dispersion (SSD). Experiments to measure and control the irradiation uniformity are also highlighted. Following the discussion of irradiation uniformity, a brief review of coronal physics is given, includ… more

Date: April 1, 1991

Creator: McCrory, R. L.

Item Type: Report

Partner: UNT Libraries Government Documents Department

open access

An Evaluation of the Failure of a PWR Lower Head During a Core Meltdown Accident

This paper presents an analysis of ablation of lower vessel head during a core meltdown accident. The analysis if limited to PWR systems with no penetration tubes attached to the lower vessel head. The case considered is characterized by the discharge of a corium jet at a relatively slow rate into the lower plenum. The assumption of the breakup of the jet stream results in the solidification of debris particles and the formation of a debris bed thermally attacking the lower head wall. Detailed … more

Date: January 1, 1992

Creator: Yang, J. W.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Initial boronization of PBX-M using ablation of solid boronized probes

The initial boronization of PBX-M was performed using the sequential ablation of two types of solid target probes. Probe-1 in a mushroom shape consisted of a 10.7% boronized 2-D C-C composite containing 3.6 g of boron in a B[sub 4]C binder. Probe-2 in a rectangular shape consisted of an 86% boronized graphite felt composite containing 19.5 g of 40 [mu] boron particles. After boronization with Probe-1, the loop voltage during 1 MW neutral beam heated plasmas decreased 27% and volt-sec consumptio… more

Date: May 1, 1993

Creator: Kugel, H. W.; Hirooka, Y.; Kaita, R.; Kaye, S.; Khandagle, M. (California Univ., Los Angeles, CA (United States). Inst. of Plasma and Fusion Research); Timberlake, J. et al.

Item Type: Report

Partner: UNT Libraries Government Documents Department

open access

Analyses in Support of Z-IFE: LLNL Progress Report for FY-04

During the last quarter of FY2004, Lawrence Livermore National Laboratory (LLNL) conducted a brief study of power plant options for a z-pinch-based inertial fusion energy (Z-IFE) power plant. Areas that were covered include chamber design, thick-liquid response, neutronics and activation, and systems studies. This report summarizes the progress made in each of these areas, provides recommendations for improvements to the basic design concept, and identifies future work that is needed. As a star… more

Date: October 6, 2004

Creator: Meier, W; Abbott, R; Latkowski, J; Moir, R; Reyes, S & Schmitt, R

Item Type: Report

Partner: UNT Libraries Government Documents Department

open access

Comparison of Machining with Long-Pulse Green and Ultrashort Pulse Lasers

(1) LLNL measured the material removal rate from stainless steel, silicon carbide, rhenium, N5, hastalloy X, and titanium as a function of pulse fluence at a wavelength of 810 nm for pulse durations of 150 fs, 1.5 ps, 20 ps, and 500 ps. The spot size of the beam used was 150 microns in diameter and the nominal material thickness was 1-2 mm. These experiments were performed on the existing 1 kHz laser system. Holes of different penetration depths were obtained to ascertain change in removal rate… more

Date: May 18, 2001

Creator: Wynne, A E & Stuart, B C

Item Type: Report

Partner: UNT Libraries Government Documents Department

open access

Computational Simulations of High Intensity X-Ray Matter Interaction

Free electron lasers have the promise of producing extremely high-intensity short pulses of coherent, monochromatic radiation in the 1-10 keV energy range. For example, the Linac Coherent Light Source at Stanford is being designed to produce an output intensity of 2 x 10{sup 14} W/cm{sup 2} in a 230 fs pulse. These sources will open the door to many novel research studies. However, the intense x-ray pulses may damage the optical components necessary for studying and controlling the output. At t… more

Date: August 2, 2001

Creator: London, R. A.; Rionta, R.; Tatchyn, R. & Roessler, S.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Rep-Rated X-ray Damage and Ablation Experiments for IFE and ICF Applications

The response of materials to high-dose x-ray exposures needs to be understood for inertial fusion energy (IFE) and inertial confinement fusion applications, where the requirements for IFE are considerably more stringent. In the IFE context, x-ray damage and/or small levels of ablation are of importance for component survivability, generation of debris, and contamination. Ablation quantities of even 1 angstrom per shot would result in material removal of more than 1 cm per year of operation. If … more

Date: September 8, 2003

Creator: Latkowski, J. F.; Abbott, R. P.; Payne, S. A.; Reyes, S.; Schmitt, R. C. & Speth, J. A.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Effect of stress-triaxiality on void growth in dynamic fracture of metals: a molecular dynamics study

The effect of stress-triaxiality on growth of a void in a three dimensional single-crystal face-centered-cubic (FCC) lattice has been studied. Molecular dynamics (MD) simulations using an embedded-atom (EAM) potential for copper have been performed at room temperature and using strain controlling with high strain rates ranging from 10{sup 7}/sec to 10{sup 10}/sec. Strain-rates of these magnitudes can be studied experimentally, e.g. using shock waves induced by laser ablation. Void growth has be… more

Date: October 7, 2003

Creator: Seppala, E T; Belak, J & Rudd, R E

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Hydro-Coupling Effects on Compression Symmetry in Gas-Filled Hohlraum Experiments at the Omega Laser

Ignition hohlraum designs use low Z gas fill to slow down the inward progress of high Z ablated plasma from the hohlraum walls preventing large laser spot motion and capsule drive asymmetries. In order to optimize the ignition design, the gas hydro-coupling effect to a fusion capsule asymmetry is presently being assessed in experiments at the Omega laser facility with gas filled hohlraums and foam balls. Our experiments measure the effects of the pressure spike that is generated by direct gas h… more

Date: August 26, 2003

Creator: Dewalds, E. L.; Pollaine, S. W.; Landen, O. L.; Amendt, P. A.; Turner, R. E.; Wallace, R. et al.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Simulating Marvel with the Stun Code

MARVEL, a nuclear-driven shock-tube experiment, consisted of a 2.2 kiloton nuclear explosive detonated 176 meters underground at one end of a 122-meter long, 1-meter diameter horizontal tunnel. Vaporization of material in the immediate vicinity of the explosive provided the source of high-energy driver gas. The driven gas was the ambient atmospheric air in the tunnel. The event was staged as an experimental and calculational study of the time dependent .ow of energy in the tunnel and surroundin… more

Date: May 23, 2001

Creator: Glenn, L A

Item Type: Report

Partner: UNT Libraries Government Documents Department

open access

Material ejection from shock-loaded free surfaces of aluminum and lead

A discussion is presented regarding interferometer experiments conducted on free surfaces which are impulsively loaded with high amplitude shock waves. It is shown that material ejection from shocked surfaces can significantly degrade interferometer experiments. In particular, loss of both light intensity and contrast of interferometer signals can result from various scattering and absorption processes occurring in a cloud of ejected material. An experimental technique is presented which allows… more

Date: October 1, 1976

Creator: Asay, J. R.

Item Type: Report

Partner: UNT Libraries Government Documents Department

open access

Laser desorption/ablation studies by resonance ionization mass spectrometry

Theory and results are presented for RIMS diagnostics of a variety of laser-materials interactions. 5 refs. 3 figs.

Date: 1988~

Creator: Nogar, N. S.; Estler, R. C.; Rowe, M. W.; Fearey, B. L. & Miller, C. M.

Item Type: Article

Partner: UNT Libraries Government Documents Department