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Dynamic response of single crystalline copper subjected to quasi-isentropic laser and gas-gun driven loading

Description: Single crystalline copper was subjected to quasi-isentropic compression via gas-gun and laser loading at pressures between 18 GPa and 59 GPa. The deformation substructure was analyzed via transmission electron microscopy (TEM). Twins and laths were evident at the highest pressures, and stacking faults and dislocation cells in the intermediate and lowest pressures, respectively. The Preston-Tonks-Wallace (PTW) constitutive description was used to model the slip-twinning process in both cases.
Date: May 22, 2006
Creator: Meyers, M; Jarmakani, H; McNaney, J; Schneider, M; Nguyen, J & Kad, B
Partner: UNT Libraries Government Documents Department

Transitions of Dislocation Glide to Twinning and Shear Transformation in Shock-Deformed Tantalum

Description: Recent TEM studies of deformation substructures developed in tantalum and tantalum-tungsten alloys shock-deformed at a peak pressure {approx}45 GPa have revealed the occurrence of shock-induced phase transformation [i.e., {alpha} (bcc) {yields} {omega} (hexagonal) transition] in addition to shock-induced deformation twinning. The volume fraction of twin and {omega} domains increases with increasing content of tungsten. A controversy arises since tantalum exhibits no clear equilibrium solid-state phase transformation under hydrostatic pressures up to 174 GPa. It is known that phase stability of a material system under different temperatures and pressures is determined by system free energy. That is, a structural phase that has the lowest free energy will be stable. For pressure-induced phase transformation under hydrostatic-pressure conditions, tantalum may undergo phase transition when the free energy of a competing phase {omega} becomes smaller than that of the parent phase {alpha} above a critical pressure (P{sub eq}), i.e., the equilibrium {alpha} {yields} {omega} transition occurs when the pressure increases above P{sub eq}. However, it is also known that material shocked under dynamic pressure can lead to a considerable increase in temperature, and the higher the applied pressure the higher the overheat temperature. This means a higher pressure is required to achieve an equivalent volume (or density) in dynamic-pressure conditions than in hydrostatic-pressure conditions. Accordingly, P{sub eq} for {alpha} {yields} {omega} transition is anticipated to increase under dynamic-pressure conditions as a result of the temperature effect. Although no clear equilibrium transition pressure under hydrostatic-pressure conditions is reported for tantalum, it is reasonable to assume that Peq under dynamic-pressure conditions will be considerably higher than that under hydrostatic-pressure conditions if there is a pressure-induced {alpha} {yields} {omega} transition in tantalum. The observation of {alpha} {yields} {omega} transition in shock-compressed tantalum and tantalum-tungsten alloys at {approx}45 GPa in fact reveals the occurrence of a non-equilibrium phase ...
Date: October 19, 2009
Creator: Hsiung, L L; Campbell, G H & McNaney, J M
Partner: UNT Libraries Government Documents Department

Materials Response under extreme conditions

Description: Solid state experiments at extreme pressures, 10-100 GPa (0.1-1 Mbar) and strain rates (10{sup 6}-10{sup 8} s{sup -1}) are being developed on high-energy laser facilities. The goal is an experimental capability to test constitutive models for high-pressure, solid-state strength for a variety of materials. Relevant constitutive models are discussed, and our progress in developing a quasi-isentropic, ramped-pressure, shockless drive is given. Designs to test the constitutive models with experiments measuring perturbation growth due to the Rayleigh-Taylor instability in solid-state samples are presented.
Date: October 6, 2005
Creator: Remington, B A; Lorenz, K T; Pollaine, S & McNaney, J M
Partner: UNT Libraries Government Documents Department

Study of the neutron damage on electronics at the National Ignition Facility

Description: The NIF environment is very complex leading to a large and non trivial radiation background. A shield surrounding the electronics is required to lower the neutron background to less than 1e7 n/cm{sup 2}. Moving electronics to behind the 6 foot-thick target bay wall is the best shield.
Date: October 28, 2010
Creator: Dauffy, L S; Mcnaney, J M & Khater, H Y
Partner: UNT Libraries Government Documents Department

Deformation of nanocrystalline materials at ultrahigh strain rates - microstructure perspective in nanocrystalline nickel

Description: Nanocrystalline materials with grain sizes smaller than 100 nm have attracted extensive research in the past decade. Due to their high strength, these materials are good candidates for high pressure shock loading experiments. In this paper, we investigated the microstructural evolutions of nanocrystalline nickel with grain sizes of 10-50 nm, shock-loaded in a range of pressures (20-70 GPa). A laser-driven isentropic compression process was applied to achieve high shock-pressures in a timescale of nanoseconds and thus the high-strain-rate deformation of nanocrystalline nickel. Postmortem transmission electron microscopy (TEM) examinations reveal that the nanocrystalline structures survive the shock deformation and that dislocation activity is the prevalent deformation mechanism when the grain sizes are larger than 30 nm, without any twinning activity at twice the stress threshold for twin formation in micrometer-sized polycrystals. However, deformation twinning becomes an important deformation mode for 10-20 nm grain-sized samples.
Date: April 10, 2006
Creator: Wang, Y; Bringa, E; Victoria, M; Caro, A; McNaney, J; Smith, R et al.
Partner: UNT Libraries Government Documents Department

DYNAMIC RESPONSE OF COPPER SUBJECTED TO QUASI-ISENTROPIC, GAS-GUN DRIVEN LOADING

Description: A transmission electron microscopy study of quasi-isentropic high-pressure loading (peak pressures between 18 GPa and 52 GPa) of polycrystalline and monocrystalline copper was carried out. Deformation mechanisms and defect substructures at different pressures were analyzed. Current evidence suggests a deformation substructure consisting of twinning at the higher pressures and heavily dislocated laths and dislocation cells at the intermediate and lower pressures, respectively. Evidence of stacking faults at the intermediate pressures was also found. Dislocation cell sizes decreased with increasing pressure and increased with distance away from the surface of impact.
Date: September 29, 2005
Creator: Jarmakani, H; McNaney, J M; Schneider, M S; Orlikowski, D; Nguyen, J H; Kad, B et al.
Partner: UNT Libraries Government Documents Department

DEFORMATION SUBSTRUCTURES AND THEIR TRANSITIONS IN LASER SHOCK-COMPRESSED COPPER-ALUMINUM ALLOYS

Description: It is shown that the short pulse durations (0.1-10 ns) in laser shock compression ensure a rapid decay of the pulse and quenching of the shocked sample in times that are orders of magnitude lower than in conventional explosively driven plate impact experiments. Thus, laser compression, by virtue of a much more rapid cooling, enables the retention of a deformation structure closer to the one existing during shock. The smaller pulse length also decreases the propensity for localization. Copper and copper aluminum (2 and 6 wt% Al) with orientations [001] and [{bar 1}34] were subjected to high intensity laser pulses with energy levels of 70 to 300 J delivered in an initial pulse duration of approximately 3 ns. The [001] and [{bar 1}34] orientations were chosen since they respectively maximize and minimize the number of slip systems with highest resolved shear stresses. Systematic differences of the defect substructure were observed as a function of pressure, stacking-fault energy and crystalline orientation. The changes in the mechanical properties for each condition were compared using micro- and nano-hardness measurements and correlated well with observations of the defect substructure. Three regimes of plastic deformation were identified and their transitions modeled: dislocation cells, stacking-faults, and twins. An existing constitutive description of the slip to twinning transition, based on the critical shear stress, was expanded to incorporate the effect of stacking-fault energy. A new physically-based criterion accounting for stacking-fault energy was developed that describes the transition from perfect loop to partial loop homogeneous nucleation, and consequently from cells to stacking-faults. These calculations predict transitions that are in qualitative agreement with the effect of SFE.
Date: October 17, 2007
Creator: Meyers, M A; Schneider, M S; Jarmakani, H; Kad, B; Remington, B A; Kalantar, D H et al.
Partner: UNT Libraries Government Documents Department

Ultrafast, In Situ Probing of Shocked Solids at the Mesoscale and Beyond: A New Paradigm for Materials Dynamics

Description: Understanding material response under dynamic conditions and extreme pressures at the lattice level is important for being able to generate predictive models of material response. Despite many decades of study, material behavior is primarily inferred from bulk measurements on dynamically loaded samples or the microstructure from recovery experiments and not determined from lattice level measurements made in-situ at the relevant length scale of the governing physics. In the work described here, we report on progress made in advancing this frontier with research conducted under LDRD 04-ERD-071. Specifically, we present advances in, and applications of, dynamic x-ray diffraction, Extended X-ray Absorption Fine Structure and dynamic transmission electron microscopy.
Date: February 15, 2007
Creator: Lorenzana, H; Belak, J; Campbell, G; King, W; Nikkel, D; Bradley, K et al.
Partner: UNT Libraries Government Documents Department

ULTRA-HIGH STRENGTH IN NANOCRYSTALLINE MATERIALS UNDER SHOCK LOADING

Description: Molecular dynamics simulations of nanocrystalline (nc) copper under shock loading show an unexpected ultra-high strength behind the shock front. The strength at high pressure can be up to twice the value at low pressure, for all grain sizes studied here (5-50 nm grains, with up to {approx}4 10{sup 8} atoms). Partial and perfect dislocations, twinning, and debris from dislocation interactions are found behind the shock front. Results are interpreted in terms of the pressure dependence of both deformation mechanisms active at these grain sizes, namely dislocation plasticity and grain boundary sliding. These simulations, together with new shock experiments on nc nickel, raise the possibility of achieving ultra-hard materials during and after shock loading.
Date: April 11, 2005
Creator: Bringa, E M; Caro, A; Wang, Y M; Victoria, M; McNaney, J; Remington, B A et al.
Partner: UNT Libraries Government Documents Department

Evaluation of Mo-SiO{sub 2} continuous FGM`s. Final report

Description: The TOTO sponsored program at LBL involved characterization of continuous Mo-SiO{sub 2} FGMs in terms of microstructure, mechanical and thermal properties and corrosion resistance which would relate to the steady state, high temperature performance as well as the heating and cooling transients that occur at the beginning and end of operation in various applications.
Date: September 1, 1997
Creator: Tomsia, A.P.; Cannon, R.M.; McNaney, J.M.; Ishibashi, H.; Saiz, E.; MoberlyChan, W. et al.
Partner: UNT Libraries Government Documents Department

In-situ probing of lattice response in shock compressed materials using x-ray diffraction

Description: Lattice level measurements of material response under extreme conditions are required to build a phenomenological understanding of the shock response of solids. We have successfully used laser produced plasma x-ray sources coincident with laser driven shock waves to make in-situ measurements of the lattice response during shock compression for both single crystal and polycrystalline materials. Using a detailed analysis of shocked single crystal iron which has undergone the {alpha} - {var_epsilon} phase transition we can constrain the transition mechanism to be consistent with a compression and shuffle of alternate lattice planes.
Date: July 17, 2007
Creator: Hawreliak, J; Butterfield, M; Davies, H; El-Dasher, B; Higginbotham, A; Kalantar, D et al.
Partner: UNT Libraries Government Documents Department

Epithermal Neutron Source for Neutron Resonance Spectroscopy (NRS) using High Intensity, Short Pulse Lasers

Description: A neutron source for neutron resonance spectroscopy (NRS) has been developed using high intensity, short pulse lasers. This measurement technique will allow for robust measurements of interior ion temperature of laser-shocked materials and provide insight into equation of state (EOS) measurements. The neutron generation technique uses protons accelerated by lasers off of Cu foils to create neutrons in LiF, through (p,n) reactions with {sup 7}Li and {sup 19}F. The distribution of the incident proton beam has been diagnosed using radiochromic film (RCF). This distribution is used as the input for a (p,n) neturon prediction code which is compared to experimentally measured neutron yields. From this calculation, a total fluence of 1.8 x 10{sup 9} neutrons is infered, which is shown to be a reasonable amount for NRS temperature measurement.
Date: April 22, 2010
Creator: Higginson, D P; McNaney, J M; Swift, D C; Bartal, T; Hey, D S; Pape, S L et al.
Partner: UNT Libraries Government Documents Department

High aspect ratio hard x-ray (> 100 keV) imager to measure hot electron preheat for indirectly driven capsule implosions on the National Ignition Facility

Description: We have fielded a multi-pinhole, hard x-ray (> 100 keV) imager to measure the spatially-resolved bremsstrahlung emission from energetic electrons slowing in a plastic ablator shell during indirectly driven implosions at the National Ignition Facility. These electrons are generated in laser plasma interactions, and are a source of preheat to the deuterium-tritium fuel that could limit the compressibility required for ignition and burn. Our hard x-ray imaging measurements allow to set an upper limit to the DT fuel preheat, which we find is acceptable in current capsule implosions on the NIF.
Date: May 1, 2012
Creator: Doppner, T; Dewald, E; Divol, L; Burns, S; Izumi, N; Kline, J et al.
Partner: UNT Libraries Government Documents Department

Studies of dynamic properties of shock compressed single crystals by in situ dynamic x-ray diffraction and sample recovery

Description: Laser compression provides pressures ranging from a few to hundreds of GPa at pulse durations of the order of nanoseconds or fractions thereof. The short duration ensures a rapid decay of the pulse and quenching of shocked sample in times that are orders of magnitude lower than in conventional explosively driven plate impact experiments. Systematic experiments carried out in specimens well suited for transmission electron microscopy characterization are revealing that laser compression, by virtue of a much more rapid cooling, enables the retention of a deformation structure closer to the one existing during shock. The smaller pulse length decreases the propensity for localization. Copper and copper aluminum (2 and 6 wt% Al) with orientations [001] and [ ] were subjected to high intensity laser pulses with energy levels of 70 to 300 J delivered in a pulse duration of approximately 3 ns. Systematic differences of the defect substructure were observed as a function of pressure and stacking fault energy. The changes in the mechanical properties for each condition were compared using micro- and nano-hardness measurements and correlated well with observations of the defect substructure. Three regimes of plastic deformation were identified and their transitions modeled: dislocation cells, stacking faults, and twins. An existing constitutive description of the slip to twinning transition, based on the critical shear stress, was expanded to incorporate the effect of stacking-fault energy. A new physically-based criterion accounting for stacking fault energy was developed that describes the transition from perfect loop to partial loop homogeneous nucleation, and consequently from cells to stacking faults. These calculations predict transitions that are in qualitative agreement with the effect of SFE.
Date: May 5, 2007
Creator: Meyers1, M. A.; Schneider, M. S.; Jarmakani, H.; Kad, B.; Remington2, B. A.; Kalantar, D. H. et al.
Partner: UNT Libraries Government Documents Department

National Ignition Facility (NIF) Neutron time-of-flight (nTOF) Measurements

Description: The first three of eighteen neutron time-of-flight (nTOF) channels have been installed at the National Ignition Facility (NIF). The role of these detectors includes yield, temperature, and bang time measurements. This article focuses on nTOF data analysis and quality of results obtained for the first set of experiments to use all 192 NIF beams. Targets produced up to 2 x 10{sup 10} 2.45-MeV neutrons for initial testing of the nTOF detectors. Differences in neutron scattering at the OMEGA laser facility where the detectors were calibrated and at NIF result in different response functions at the two facilities. Monte Carlo modeling shows this difference. The nTOF performance on these early experiments indicates the nTOF system with its full complement of detectors should perform well in future measurements of yield, temperature, and bang time.
Date: May 13, 2010
Creator: Lerche, R A; Glebov, V Y; Moran, M J; McNaney, J M; Kilkenny, J D; Eckart, M et al.
Partner: UNT Libraries Government Documents Department