Article
Physics, Fluids & Plasmas
V. A. Izzo
Summary: A study on dispersive shell pellet injections for disruption mitigation on the DIII-D tokamak was conducted using the 3D MHD code NIMROD. The simulations aimed to replicate a pellet velocity scan performed on the DIII-D tokamak, showing trends such as improved mitigation and increased likelihood of hot-tail runaway electron production with higher pellet speed. The simulations provided additional physics insights and discussed limitations of the current model and requirements for a predictive model.
PHYSICS OF PLASMAS
(2021)
Article
Physics, Fluids & Plasmas
Yueqiang Liu, L. Li, C. Paz-Soldan, P. B. Parks, L. L. Lao
Summary: The study found that the Rosenbluth-Putvinski model may underestimate the RE plateau current for circular-shaped plasmas, but can still predict strong runaway current avalanche production in elongated, higher current plasmas. The plasma shape, specifically elongation, has a significant impact on reducing RE avalanche production, while the effect of plasma triangularity is minor. The research reveals the complex dynamics and competing mechanisms involved in the RE avalanche process, shedding light on the foundation for future inclusion of MHD dynamics and RE amplification in modeling.
Article
Physics, Fluids & Plasmas
V. A. Izzo, I Pusztai, K. Saerkimaeki, A. Sundstrom, D. T. Garnier, D. Weisberg, R. A. Tinguely, C. Paz-Soldan, R. S. Granetz, R. Sweeney
Summary: The operation of a 3D coil driven by the current quench loop voltage for the deconfinement of runaway electrons is modeled and simulated for disruption scenarios in the SPARC and DIII-D tokamaks. Different codes are used to calculate transport coefficients and simulate the evolution of the runaway electrons. The results show that certain coil geometries can suppress the runaway current growth, but conservative transport assumptions are needed to fully suppress the current.
Article
Instruments & Instrumentation
C. Marini, J. A. Boedo, E. M. Hollmann, L. Chousal, J. Mills, Z. Popovic, I. Bykov
Summary: Two camera systems are installed on the DIII-D tokamak for viewing at 90 degrees and 225 degrees toroidal positions respectively, with different relay optics providing either stability or resolution. The cameras are shielded to reduce damage and interference, and equipped with an automated filter system and software suite for remote operation and data analysis. Spatial calibration is achieved using observable wall features with an accuracy of <= 2 cm.
REVIEW OF SCIENTIFIC INSTRUMENTS
(2023)
Article
Physics, Fluids & Plasmas
A. Lvovskiy, C. Paz-Soldan, N. W. Eidietis, A. Dal Molin, G. H. DeGrandchamp, E. M. Hollmann, J. B. Lestz, C. Liu, M. Nocente, D. Shiraki, X. D. Du
Summary: The dependencies of Alfvenic instabilities driven by runaway electrons (REs) during current quench in DIII-D on plasma and material injection parameters were investigated. The observed instabilities in the frequency range of 0.1-3 MHz are correlated with increased RE loss and may play a role in non-sustained RE beams.
Article
Physics, Fluids & Plasmas
F. Sciortino, N. T. Howard, T. Odstrcil, M. Austin, I Bykov, C. Chrystal, S. R. Haskey, J. D. Lore, A. Marinoni, E. S. Marmar, O. Meneghini, C. Paz-Soldan, P. Rodriguez-Fernandez, S. P. Smith, K. E. Thome
Summary: In this paper, the impurity transport in DIII-D diverted negative triangularity experiments is examined, and the diffusion and convection characteristics of impurities are analyzed through measurements and simulations. The results show that the negative triangularity discharges may have advantages in certain transport channels compared to L-mode, and may achieve a highly-radiative scenario with high core performance.
PLASMA PHYSICS AND CONTROLLED FUSION
(2022)
Article
Physics, Fluids & Plasmas
E. M. Hollmann, A. Bortolon, F. Effenberg, N. Eidietis, D. Shiraki, I. Bykov, B. E. Chapman, J. Chen, S. Haskey, J. Herfindal, A. Lvovskiy, C. Marini, A. McLean, T. O'Gorman, M. D. Pandya, C. Paz-Soldan, Z. Popovic
Summary: The first dynamic measurements of impurity ion diffusion coefficients in post-disruption runaway electron plateaus are presented. Results show that the diffusion coefficients in both the radial and parallel directions are larger than expected, possibly due to turbulent transport. The toroidal variation in electron density and toroidal rotation of impurity ions may also affect the radial diffusion rates.
PHYSICS OF PLASMAS
(2022)
Article
Physics, Fluids & Plasmas
E. M. Hollmann, D. Shiraki, L. Baylor, I Bykov, N. W. Eidietis, I Golovkin, J. L. Herfindal, A. Lvovskiy, A. McLean, R. A. Moyer, P. B. Parks, Z. Popovic
Summary: The formation of non-thermal electrons during the thermal quench of shattered pellet injection discharge shutdowns in the DIII-D tokamak has been studied, with indications of non-thermal electron generation during the thermal quench. The non-thermals have an effect on the deposition profile of the SPI pellets, especially at the end of the thermal quench, due to increased pellet ablation.
Article
Physics, Fluids & Plasmas
Yueqiang Liu, L. Li, C. C. Kim, L. L. Lao, P. B. Parks
Summary: Direct interactions between the n = 1 resistive internal kink instability and relativistic runaway electrons in a post thermal quench toroidal plasma were numerically investigated. The study found that runaway electrons can destabilize the resistive internal kink mode and lead to changes in the mode growth rate, affecting the RE drift orbits. The hybrid model used in the study showed less loss of relativistic electrons in the RE beam compared to the fluid model when perturbation level reaches equilibrium field.
Article
Physics, Fluids & Plasmas
J. L. Barr, B. Sammuli, D. A. Humphreys, E. Olofsson, X. D. Du, C. Rea, W. P. Wehner, M. D. Boyer, N. W. Eidietis, R. Granetz, A. Hyatt, T. Liu, N. C. Logan, S. Munaretto, E. Strait, Z. R. Wang, The DIII-D Team
Summary: Novel disruption prevention solutions, including real-time control algorithms, limited topology transitions during emergency shutdown, and emergency shutdown methods, have been developed and tested. These methods have successfully prevented vertical displacement events, improved the disruption risk during emergency shutdown after large tearing and locked modes, and developed a method to excite instabilities to form a warm, helical core post-thermal quench to avoid VDEs and runaway electron generation.
Article
Physics, Fluids & Plasmas
A. Lier, G. Papp, Ph. W. Lauber, O. Embreus, G. J. Wilkie, S. Braun
Summary: The study investigates the role of fusion-born alpha particles in driving Alfvenic instabilities in ITER disruption simulations, and explores their ability to expel runaway electron seed particles. Through simulations, it is found that the radial anisotropy of the alpha population during the disruption phase provides free energy to drive Alfvenic modes. The analysis suggests that the resulting mode amplitudes are predicted to be sufficiently large to allow for significant radial transport of runaway electrons.
Article
Physics, Fluids & Plasmas
E. M. Hollmann, L. Baylor, A. Boboc, P. Carvalho, N. W. Eidietis, J. L. Herfindal, S. Jachmich, A. Lvovskiy, C. Paz-Soldan, C. Reux, D. Shiraki, R. Sweeney
Summary: Experimental trends in thermal plasma partial recombination resulting from massive D-2 injection into high-Z (Ar) containing runaway electron (RE) plateaus in DIII-D and JET are studied. The study finds that thermal electron density drops by about 100x when partial recombination occurs, with a minimum at a D-2 density of 10(20)-10(21)m(-3). The results also show that achieving low electron density will be easier with Ar as a background impurity.
Article
Instruments & Instrumentation
A. Dal Molin, L. Fumagalli, M. Nocente, D. Rigamonti, M. Tardocchi, L. Giacomelli, E. Panontin, A. Lvovskiy, C. Paz-Soldan, N. W. Edietis, G. Gorini
Summary: The novel compact spectrometer optimized for measuring hard X rays generated by runaway electrons is designed for installation in the fan-shaped collimator of the gamma-ray imager diagnostic in the DIII-D tokamak. It features a detector based on cerium doped yttrium aluminum perovskite scintillator crystal coupled with a silicon photomultiplier, with a dynamic energy range exceeding 10 MeV and energy resolution of around 10% at 661.7 keV. The fast detector signal enables operation at counting rates over 1 MCps, with gain stability monitored in real time using a light-emitting diode. It is expected to be deployed in the upcoming DIII-D runaway electron experimental campaign.
REVIEW OF SCIENTIFIC INSTRUMENTS
(2021)
Article
Physics, Fluids & Plasmas
A. Marinoni, M. E. Austin, A. W. Hyatt, S. Saarelma, F. Scotti, Z. Yan, C. Chrystal, S. Coda, F. Glass, J. M. Hanson, A. G. McLean, D. C. Pace, C. Paz-Soldan, C. C. Petty, M. Porkolab, L. Schmitz, F. Sciortino, S. P. Smith, K. E. Thome, F. Turco
Summary: Discharges at negative triangularity on the DIII-D tokamak sustain normalized confinement and pressure levels typical of standard H-mode scenarios without developing an edge pressure pedestal, showing weaker power degradation of confinement compared to traditional scaling laws. This absence of an edge pedestal offers various benefits and technological advantages, making plasmas at negative triangularity potentially suitable for future fusion reactors.
Article
Physics, Fluids & Plasmas
J. M. Hanson, F. Turco, T. C. Luce, G. A. Navratil, E. J. Strait
Summary: Measurements of plasma response to external perturbations in DIII-D ITER baseline scenario demonstration discharges show increasing amplitude before disruption, with simulations and experimental data having some consistency, but the stability of experimental discharges is lower than expected.
PHYSICS OF PLASMAS
(2021)
Article
Physics, Fluids & Plasmas
V. A. Izzo, P. B. Parks, N. W. Eidietis, D. Shiraki, E. M. Hollmann, N. Commaux, R. S. Granetz, D. A. Humphreys, C. J. Lasnier, R. A. Moyer, C. Paz-Soldan, R. Raman, E. J. Strait
Article
Physics, Multidisciplinary
Mordechai Kornbluth, Chris A. Marianetti
PHYSICAL REVIEW LETTERS
(2015)
Article
Physics, Fluids & Plasmas
V. A. Izzo, P. B. Parks
PHYSICS OF PLASMAS
(2017)
Article
Nanoscience & Nanotechnology
Andrew S. Westover, Andrew K. Kercher, Mordechai Kornbluth, Michael Naguib, Max J. Palmer, David A. Cullen, Nancy J. Dudney
ACS APPLIED MATERIALS & INTERFACES
(2020)
Article
Physics, Fluids & Plasmas
V. A. Izzo
Article
Physics, Multidisciplinary
Nicola Molinari, Yu Xie, Ian Leifer, Aris Marcolongo, Mordechai Kornbluth, Boris Kozinsky
Summary: The method uses spectral decomposition of short-time ionic displacement covariance to accelerate computations of ionic conductivity and reduce uncertainty. It demonstrates robustness through mathematical and numerical proofs, and is applied to realistic electrolyte materials.
PHYSICAL REVIEW LETTERS
(2021)
Article
Physics, Fluids & Plasmas
V. A. Izzo
Summary: A study on dispersive shell pellet injections for disruption mitigation on the DIII-D tokamak was conducted using the 3D MHD code NIMROD. The simulations aimed to replicate a pellet velocity scan performed on the DIII-D tokamak, showing trends such as improved mitigation and increased likelihood of hot-tail runaway electron production with higher pellet speed. The simulations provided additional physics insights and discussed limitations of the current model and requirements for a predictive model.
PHYSICS OF PLASMAS
(2021)
Article
Chemistry, Physical
Cheol Woo Park, Mordechai Kornbluth, Jonathan Vandermause, Chris Wolverton, Boris Kozinsky, Jonathan P. Mailoa
Summary: GNNFF framework accurately predicts atomic forces using machine learning, achieving high performance and computational speed across various material systems, and accurately predicting the forces of large MD systems after training on smaller systems. The Li diffusion coefficient obtained through MD simulation using this framework shows good accuracy compared to AIMD.
NPJ COMPUTATIONAL MATERIALS
(2021)
Article
Multidisciplinary Sciences
Simon Batzner, Albert Musaelian, Lixin Sun, Mario Geiger, Jonathan P. Mailoa, Mordechai Kornbluth, Nicola Molinari, Tess E. Smidt, Boris Kozinsky
Summary: This paper introduces an E(3)-equivariant deep learning method for accelerating molecular dynamics simulations. The method shows state-of-the-art accuracy and remarkable sample efficiency in faithfully describing the dynamics of complex systems. The Neural Equivariant Interatomic Potentials (NequIP) approach employs E(3)-equivariant convolutions to interact with geometric tensors, resulting in a more information-rich and faithful representation of atomic environments. NequIP outperforms existing models with significantly fewer training data, challenging the commonly held belief about the necessity of massive training sets for deep neural networks.
NATURE COMMUNICATIONS
(2022)
Article
Physics, Fluids & Plasmas
V. A. Izzo, I Pusztai, K. Saerkimaeki, A. Sundstrom, D. T. Garnier, D. Weisberg, R. A. Tinguely, C. Paz-Soldan, R. S. Granetz, R. Sweeney
Summary: The operation of a 3D coil driven by the current quench loop voltage for the deconfinement of runaway electrons is modeled and simulated for disruption scenarios in the SPARC and DIII-D tokamaks. Different codes are used to calculate transport coefficients and simulate the evolution of the runaway electrons. The results show that certain coil geometries can suppress the runaway current growth, but conservative transport assumptions are needed to fully suppress the current.
Article
Multidisciplinary Sciences
Albert Musaelian, Simon Batzner, Anders Johansson, Lixin Sun, Cameron J. Owen, Mordechai Kornbluth, Boris Kozinsky
Summary: This study introduces Allegro, a local equivariant deep neural network interatomic potential architecture that achieves excellent accuracy and scalability in quantum chemistry and molecular simulations.
NATURE COMMUNICATIONS
(2023)
Article
Chemistry, Physical
Andrew S. Westover, Mordechai Kornbluth, Takeshi Egami, Jue Liu, Sergiy Kalnaus, Dong Ma, Andrew K. Kercher, Joerg C. Neuefeind, Michelle Everett, Victor Torres, Steve W. Martin, Boris Kozinsky, Nancy J. Dudney
Summary: In this study, the structure of amorphous ionic glasses LiPON and LiSiPON with high Li content was characterized. The materials were found to have an inverted structure with isolated polyanion tetrahedra or polyanion dimers in a Li+ matrix, as observed through ab initio molecular dynamics simulations. The inverted structure resulted in significant medium-range ordering, indicated by sharp diffraction peaks and periodic structural oscillation. Additionally, the addition of Si increased disorder in the polyanion substructure but enhanced ordering in the O substructure, resulting in a glassy material that is mechanically stiff and ductile on the nanoscale.
CHEMISTRY OF MATERIALS
(2023)
Article
Chemistry, Physical
Young-Woon Byeon, Jonathan Mailoa, Mordechai Kornbluth, Gi-Hyeok Lee, Zijian Cai, Yingzhi Sun, Wanli Yang, Christina Johnston, Jake Christensen, Soo Kim, Lei Cheng, Haegyeom Kim
Summary: This study suggests that Mg-Ti-O compounds in the chemical space exhibit high electrical conductivity and corrosion stability, making them potential catalyst supporters for polymer electrolyte membrane fuel cells.
JOURNAL OF MATERIALS CHEMISTRY A
(2022)
Article
Computer Science, Artificial Intelligence
Jonathan P. Mailoa, Mordechai Kornbluth, Simon Batzner, Georgy Samsonidze, Stephen T. Lam, Jonathan Vandermause, Chris Ablitt, Nicola Molinari, Boris Kozinsky
NATURE MACHINE INTELLIGENCE
(2019)
Article
Materials Science, Multidisciplinary
Lyuwen Fu, Mordechai Kornbluth, Zhengqian Cheng, Chris A. Marianetti