9 results on '"Z.J. Bergstrom"'
Search Results
2. Perspectives on multiscale modelling and experiments to accelerate materials development for fusion
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Brian D. Wirth, Sergei L. Dudarev, Enrique Martínez, Michael P. Short, Wahyu Setyawan, Daniel R. Mason, Shenyang Y. Hu, Tomohito Tsuru, Tomoaki Suzudo, M.J. Caturla, Yanwen Zhang, Emmanuelle A. Marquis, Steven J. Zinkle, Pär Olsson, David J. Senor, Mihai-Cosmin Marinica, Jason R. Trelewicz, R.J. Kurtz, Fei Gao, Gary S. Was, Z.J. Bergstrom, Xunxiang Hu, Andrey Litnovsky, Kazuto Arakawa, Li Yang, Yury N. Osetskiy, Mark R. Gilbert, Alexandra Goryaeva, Ba Nghiep Nguyen, Jaime Marian, Culham Centre for Fusion Energy (CCFE), Shimane University, The University of Tennessee [Knoxville], Universidad de Alicante, University of Michigan [Ann Arbor], University of Michigan System, Service de recherches de métallurgie physique (SRMP), Département des Matériaux pour le Nucléaire (DMN), CEA-Direction des Energies (ex-Direction de l'Energie Nucléaire) (CEA-DES (ex-DEN)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-CEA-Direction des Energies (ex-Direction de l'Energie Nucléaire) (CEA-DES (ex-DEN)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay, Pacific Northwest National Laboratory, Richland, WA, USA, Materials Science and Technology Division [Oak Ridge], Oak Ridge National Laboratory [Oak Ridge] (ORNL), UT-Battelle, LLC-UT-Battelle, LLC, Forschungszentrum Jülich GmbH | Centre de recherche de Juliers, Helmholtz-Gemeinschaft = Helmholtz Association, The National Research Nuclear University MEPhI (Moscow Engineering Physics Institute) [Moscow, Russia], University of California [Los Angeles] (UCLA), University of California, Clemson University, Royal Institute of Technology [Stockholm] (KTH ), Massachusetts Institute of Technology (MIT), Japan Atomic Energy Agency [Ibaraki] (JAEA), Stony Brook University [SUNY] (SBU), State University of New York (SUNY), UT-Battelle, LLC, European Project: 633053,H2020,EURATOM-Adhoc-2014-20,EUROfusion(2014), Universidad de Alicante. Departamento de Física Aplicada, Física de la Materia Condensada, Grupo de Nanofísica, and University of California (UC)
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Nuclear and High Energy Physics ,Computer science ,02 engineering and technology ,Fusion materials ,Experimental characterisation ,7. Clean energy ,01 natural sciences ,Hydrogen and helium ,010305 fluids & plasmas ,Multiscale modelling ,Radiation damage ,defect evolution ,Development (topology) ,Física Aplicada ,0103 physical sciences ,General Materials Science ,hydrogen and helium ,Cluster analysis ,Fusion ,experimental characterisation ,021001 nanoscience & nanotechnology ,First generation ,Nuclear Energy and Engineering ,13. Climate action ,radiation damage ,Systems engineering ,fusion materials ,[PHYS.COND.CM-MS]Physics [physics]/Condensed Matter [cond-mat]/Materials Science [cond-mat.mtrl-sci] ,multiscale modelling ,0210 nano-technology ,Defect evolution - Abstract
Prediction of material performance in fusion reactor environments relies on computational modelling, and will continue to do so until the first generation of fusion power plants come on line and allow long-term behaviour to be observed. In the meantime, the modelling is supported by experiments that attempt to replicate some aspects of the eventual operational conditions. In 2019, a group of leading experts met under the umbrella of the IEA to discuss the current position and ongoing challenges in modelling of fusion materials and how advanced experimental characterisation is aiding model improvement. This review draws from the discussions held during that workshop. Topics covering modelling of irradiation-induced defect production and fundamental properties, gas behaviour, clustering and segregation, defect evolution and interactions are discussed, as well as new and novel multiscale simulation approaches, and the latest efforts to link modelling to experiments through advanced observation and characterisation techniques. MRG, SLD, and DRM acknowledge funding by the RCUK Energy Programme [grant number EP/T012250/1]. Part of this work has been carried out within the framework of the EUROFusion Consortium and has received funding from the Euratom research and training programme 2014–2018 and 2019–2020 under grant Agreement No. 633053. The views and opinions expressed herein do not necessarily reflect those of the European Commission. JRT acknowledges funding from the US Department of Energy (DOE) through grant DE-SC0017899. ZB, LY,BDW, and SJZ acknowledge funding through the US DOE Fusion Energy Sciences grant DE-SC0006661ZB, LY and BDW also were partially supported from the US DOE Office of Science, Office of Fusion Energy Sciences and Office of Advanced Scientific Computing Research through the Scientific Discovery through Advanced Computing (SciDAC) project on Plasma-Surface Interactions. JMa acknowledges support from the US-DOEs Office of Fusion Energy Sciences (US-DOE), project DE-SC0019157. Pacific Northwest National Laboratory is operated by Battelle Memorial Institute for the US Department of Energy (DOE) under contract DE-AC05-76RL01830. YO and YZ were supported as part of the Energy Dissipation to Defect Evolution (EDDE), an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, Basic Energy Sciences under contract number DE-AC05-00OR22725. TS and TT are supported by JSPS KAKENHI Grant Number 19K05338.
- Published
- 2021
3. Effect of interatomic potential on the energetics of hydrogen and helium-vacancy complexes in bulk, or near surfaces of tungsten
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Li Yang, Z.J. Bergstrom, and Brian D. Wirth
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Nuclear and High Energy Physics ,Materials science ,Hydrogen ,Binding energy ,Thermodynamics ,chemistry.chemical_element ,Interatomic potential ,02 engineering and technology ,021001 nanoscience & nanotechnology ,01 natural sciences ,010305 fluids & plasmas ,Molecular dynamics ,Nuclear Energy and Engineering ,chemistry ,Vacancy defect ,0103 physical sciences ,Atom ,General Materials Science ,Density functional theory ,0210 nano-technology ,Embedded atom model - Abstract
Hydrogen (H) trapping by helium-vacancy (He V) complexes in bulk and the near surface region of tungsten (W) have been investigated by molecular statics calculations that evaluate two different W H interatomic potentials, which use the same W He, He He and He H potentials. One of the W H potentials is a bond-order potential (BOP) developed by Juslin et al., while the other is an embedding atom method (EAM) potential developed by Wang et al.. Both potentials overestimate the H binding energies to He clusters in bulk W, as compared to DFT calculations, but properly predict the functional form of the H binding energies to He clusters with increasing number of He and H. The BOP simulations reveal that H binding energies to HexV complexes generally increase with increasing number of He. However, the EAM results indicate that the H binding energy as a function of number of He depends on the number of H, and the H binding energies change slightly at high He content. Compared with available DFT data, both BOP and EAM underestimate the H binding energies to HexV2Hm complexes. The BOP reproduces the He formation energy below a W surface, while the EAM potential better reproduces the H formation energy and the interactions between H and He V complexes. Based on these comparisons, we determine that the EAM potential is more accurate than BOP for large-scale molecular dynamics simulations of W He H interactions. The EAM potential predicts that the difference in the average binding energies of H to stable He V complexes near the W surface is less than 0.2 eV and the difference decreases with increasing He content. Thus, the EAM potential indicates that the effect of surfaces on H binding energies to large He V complexes below the W surfaces can be ignored.
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- 2018
4. Experimental characterization of hydrogen adsorption sites for H/W(111) using low energy ion scattering
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Chun-Shang Wong, Brian D. Wirth, Z.J. Bergstrom, Robert Kolasinski, and Josh A. Whaley
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Physics ,Recoil ,Low-energy ion scattering ,Hydrogen ,chemistry ,Scattering ,chemistry.chemical_element ,Density functional theory ,Spectroscopy ,Molecular physics ,Atomic spacing ,Ion - Abstract
Low energy ion scattering (LEIS) and direct recoil spectroscopy (DRS) are among the few experimental techniques that allow for the direct detection of hydrogen on a surface. The interpretation of LEIS and DRS measurements, however, is often made difficult by complexities that can arise from complicated scattering processes. Previously, these complexities were successfully navigated to identify the exact binding configurations of hydrogen on a few surfaces using a simple channeling model for the projectile ion along the surface. For the W(111) surface structure, this simple channeling model breaks down due to the large lateral atomic spacing on the surface and small interlayer spacing. Instead, our observed hydrogen recoil signal can only be explained by considering not just channeling along the surface but also scattering from subsurface atoms. Using this more complete model, together with molecular dynamics (MD) simulations, we determine that hydrogen adsorbs to the bond-centered site for the W(111)$+\text{H}$(ads) system. Additional MD simulations were performed to further constrain the adsorption site to a height $h=1.0\ifmmode\pm\else\textpm\fi{}0.1\phantom{\rule{3.33333pt}{0ex}}\AA{}$ and a position ${d}_{\mathrm{BC}}=1.6\ifmmode\pm\else\textpm\fi{}0.1\phantom{\rule{3.33333pt}{0ex}}\AA{}$ along the bond between neighbors in first and second layers. Our determination of the hydrogen adsorption site is consistent with density functional theory simulation results in the literature.
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- 2019
5. The mobility of small, over-pressurized helium bubbles in tungsten at 2000 K
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Z.J. Bergstrom, Enrique Martínez, and Danny Perez
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Nuclear and High Energy Physics ,Range (particle radiation) ,Materials science ,Bubble ,Nucleation ,chemistry.chemical_element ,Tungsten ,Thermal diffusivity ,Molecular physics ,Nuclear Energy and Engineering ,chemistry ,Frenkel defect ,General Materials Science ,Diffusion (business) ,Helium - Abstract
Fusion reactor environments inevitably lead to the formation of high-pressure helium bubbles whose nucleation, growth, and diffusion strongly impact the performance of plasma-facing components. This research describes a diffusion mechanism of over-pressurized bubbles via a sequence of Frenkel pair nucleation, self-interstitial migration, and Frenkel pair annihilation. Molecular dynamics was used to simulate the diffusion of small bubbles in tungsten at 2000 K with helium-per-vacancy ratios in the range of 4.5 to 7. The diffusion coefficients are calculated and their dependence on helium content, number of vacancies, and number of attached self-interstitials is characterized. It is found that bubbles are most mobile when the nucleation/annihilation rates of Frenkel pairs are nearly equal and when the bubbles nucleate and annihilate a single self-interstitial. All bubbles experience a peak diffusivity, which can be as high as 10 − 11 m 2 /s decreasing with bubble size. The calculated diffusion coefficients provide valuable insight into the mobility of small, high-pressure bubbles, and can be used as input parameters in mesoscale models to improve predictions of plasma-surface interactions. (LA-UR-21-21881)
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- 2021
6. An ab-initio study of hydrogen trapping energetics at BCC tungsten metal-noble gas interfaces
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Brian D. Wirth, Z.J. Bergstrom, and Li Yang
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Nuclear and High Energy Physics ,Argon ,Materials science ,Hydrogen ,Physics::Instrumentation and Detectors ,Binding energy ,chemistry.chemical_element ,Noble gas ,02 engineering and technology ,Tungsten ,021001 nanoscience & nanotechnology ,01 natural sciences ,010305 fluids & plasmas ,Neon ,Nuclear Energy and Engineering ,chemistry ,Chemical physics ,0103 physical sciences ,Physics::Atomic and Molecular Clusters ,General Materials Science ,Density functional theory ,0210 nano-technology ,Helium - Abstract
Density functional theory (DFT) calculations have been performed to assess the trapping and segregation strength of hydrogen (H) to noble gas interfaces in tungsten (W). These calculations consist of a supercell containing a slab of BCC W and an initial lattice of FCC noble gas atoms. The interfaces included noble gases of helium, neon, and argon, with densities in the range of 1-4 atoms-per-vacancy (V), and W surface orientations of (100), (110), and (111). We report on the binding energy of H to these interfaces as well as the modification to the migration barriers in the W slab, which together provide information on the segregation strength and de-trapping energy for H at noble gas bubbles. These calculations indicate that the binding energy of H to W-noble gas interfaces varies with surface orientation and decreases with increasing gas density; whereas the H migration energy is sensitive to the noble gas density, surface orientation, and diffusion pathway, and typically increases with gas density. Together, the de-trapping energy of H to these interfaces is shown to depend less significantly on noble gas density. These DFT calculations provide valuable first-principles energetics necessary for mesoscale models, and provide insight into the temperatures required to de-trap tritium from He bubbles in fusion plasma facing components.
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- 2021
7. A Molecular Dynamics Study of Subsurface Hydrogen-Helium Bubbles in Tungsten
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Brian D. Wirth, Z.J. Bergstrom, and Mary Alice Cusentino
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010302 applied physics ,Nuclear and High Energy Physics ,Materials science ,Hydrogen ,Mechanical Engineering ,Divertor ,chemistry.chemical_element ,Tungsten ,Fusion power ,01 natural sciences ,Physics::Geophysics ,010305 fluids & plasmas ,Ion ,Molecular dynamics ,Nuclear Energy and Engineering ,chemistry ,Physics::Plasma Physics ,0103 physical sciences ,General Materials Science ,Physics::Atomic Physics ,Hydrogen bubble ,Atomic physics ,Helium ,Civil and Structural Engineering - Abstract
Fusion reactor materials experience high ion fluxes and operating temperatures, which will ultimately produce subsurface helium and hydrogen bubbles in the tungsten divertor that can cause surface ...
- Published
- 2017
8. Performance of the Versatile Array of Neutron Detectors at Low Energy (VANDLE)
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M. Matos, J. C. Blackmon, David Walter, F. Raiola, R. Ikeyama, J. Allen, S. V. Paulauskas, R. Grzywacz, D. W. Bardayan, N. T. Brewer, Catalin Matei, S. V. Ilyushkin, I. Spassova, Z.J. Bergstrom, W. A. Peters, E. Merino, R. L. Kozub, F. Sarazin, M. E. Howard, B. Manning, Carl R. Brune, M. Madurga, S. Taylor, C.S. Reingold, Patrick O'Malley, J.M. Allen, P. Copp, Jolie Cizewski, and T. N. Massey
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Physics ,Nuclear and High Energy Physics ,010308 nuclear & particles physics ,business.industry ,Detector ,Modular design ,01 natural sciences ,Neutron temperature ,Neutron spectroscopy ,Data acquisition ,0103 physical sciences ,Neutron detection ,Optoelectronics ,Neutron ,Electronics ,Nuclear Experiment ,010306 general physics ,business ,Instrumentation - Abstract
The Versatile Array of Neutron Detectors at Low Energy (VANDLE) is a new, highly efficient plastic-scintillator array constructed for decay and transfer reaction experimental setups that require neutron detection. The versatile and modular design allows for customizable experimental setups including beta-delayed neutron spectroscopy and (d,n) transfer reactions in normal and inverse kinematics. The neutron energy and prompt-photon discrimination is determined through the time of flight technique. Fully digital data acquisition electronics and integrated triggering logic enables some VANDLE modules to achieve an intrinsic efficiency over 70% for 300-keV neutrons, measured through two different methods. A custom Geant4 simulation models aspects of the detector array and the experimental setups to determine efficiency and detector response. A low detection threshold, due to the trigger logic and digitizing data acquisition, allowed us to measure the light-yield response curve from elastically scattered carbon nuclei inside the scintillating plastic from incident neutrons with kinetic energies below 2 MeV.
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- 2016
9. Hydrogen interactions with low-index surface orientations of tungsten
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Brian D. Wirth, Congyi Li, Z.J. Bergstrom, Blas P. Uberuaga, and German D. Samolyuk
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Materials science ,Hydrogen ,Refractory metals ,chemistry.chemical_element ,02 engineering and technology ,Tungsten ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,01 natural sciences ,Dissociation (chemistry) ,Adsorption ,chemistry ,Transition metal ,Chemical physics ,0103 physical sciences ,Molecule ,General Materials Science ,Density functional theory ,010306 general physics ,0210 nano-technology - Abstract
We report on density functional theory calculations that have been performed to systematically investigate the hydrogen-surface interaction as a function of surface orientation. The interactions that were analyzed include stable atomic adsorption sites, molecular hydrogen dissociation and absorption energies, migration pathways and barriers on tungsten surfaces, and the saturation coverage limits on the (1 1 1) surface. Stable hydrogen adsorption sites were found for all surfaces. For the reconstructed W(1 0 0), there are two primary adsorption sites: namely, the long-bridge and short-bridge sites. The threefold hollow site (3F) was found to be the most stable for W(1 1 0), while the bond-centered site between the first and second layer was found to be most stable for the W(1 1 1) surface. No bound adsorption sites for H2 molecules were found for the W surfaces. Hydrogen (H) migration on both the (1 0 0) and (1 1 0) surfaces is found to have preferred pathways for 1D motion, whereas the smallest migration barrier for net migration of H on the W(1 1 1) surface leads to 2D migration. Although weaker H interactions are predicted for the W(1 1 1) surface compared to the (1 0 0) or (1 1 0) surfaces, we observe higher H surface concentrations of Θ = 4.0 at zero K, possibly due to the corrugated surface structure. These results provide insight into H adsorption, surface saturation coverage and migration mechanisms necessary to describe the evolution from the dilute limit to concentrated coverages of H.
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- 2019
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