# Publications

## 2023

- C. J. McDevitt, X. Z. Tang, C. J. Fontes, P. Sharma, and H. K. Chung.
The constraint of plasma power balance on runaway avoidance.
*Nuclear Fusion*, 63:024001.**2023**. - G. A. Wimmer and X. Tang.
Structure preserving transport stabilized compatible finite element methods for magnetohydrodynamics.
*submitted*.**2023**. - G. A. Wimmer, B. S. Southworth, T. J. Gregory, and X. Tang.
A fast algebraic multigrid solver and accurate discretization for highly anisotropic heat flux I: open field lines.
*submitted*.**2023**. - B. Zhu, X.-q. Xu, and X.-Z. Tang.
Electromagnetic turbulence simulation of tokamak edge plasma dynamics and divertor heat load during thermal quench.
*submitted*.**2023**. - Y. Li, B. Srinivasan, Y. Zhang, and X.-Z. Tang.
The plasma-sheath transition and Bohm criterion in a high recycling divertor.
*Physics of Plasmas*, 30:063505.**2023**. - Z. Jorti, Q. Tang, K. Lipnikov, and X.-Z. Tang.
A mimetic finite difference based quasi-static magnetohydrodynamic solver for force-free plasmas in tokamak disruptions.
*submitted*.**2023**. - J.-U. Chen, S. Kang, T. Bui-Thanh, and J. N. Shadid.
UNIFIED HP-HDG FRAMEWORKS FOR FRIEDRICHS' PDE SYSTEMS.
*Computers & Mathematics with Applications*, submitted.**2023**. - J. Li, Y. Zhang, and X.-Z. Tang.
Staged cooling of a fusion-grade plasma in a tokamak thermal quench.
*Nuclear Fusion*, 63:066030.**2023**. - Y. Zhang, Y. Li, B. Srinivasan, and X. Z. Tang.
Resolving the mystery of electron perpendicular temperature spike in the plasma sheath.
*Physics of Plasmas*, 30:033504.**2023**. - Y. Zhang and X. Z. Tang.
On the collisional damping of plasma velocity space instabilities.
*Physics of Plasmas*, 30:030701.**2023**. - Y. Zhang, J. Li, and X. Z. Tang.
Cooling flow regime of a plasma thermal quench.
*Europhysics Letters*, 141:54002.**2023**. - J. Rudi, M. Heldman, E. M. Constantinescu, Q. Tang, and X.-Z. Tang.
Scalable Implicit Solvers with Dynamic Mesh Adaptation for a Relativistic Drift-Kinetic Fokker-Planck-Boltzmann Model.
*submitted*.**2023**. - M. M. Crockatt and J. N. Shadid.
A Non-neutral Generalized Ohm's Law Model for Magnetohydrodynamics in the Two-Fluid Regime.
*Physics of Plasmas,*, 30:053902.**2023**. - M. Maier, J. N. Shadid, and I. Tomas.
Local-in-time structure-preserving finite-element schemes for the Euler-Poisson equations.
*Communications in Computational Physics,*, to appear.**2023**. - S. Muralikrishnan, S. Shannon, T. Bui-Thanh, and J. N. Shadid.
A multilevel block preconditioner for the HDG trace system applied to incompressible resistive MHD.
*Computer Methods in Applied Mechanics and Engineering*, 404.**2023**.

## 2022

- R. M. Park, W. Kupets, M. C. Zammit, J. Colgan, C. J. Fontes, B. S. Scheiner, E. Timmermans, X. Z. Tang, L. H. Scarlett, D. V. Fursa, I. Bray, and N. A. Garland.
Anisotropic angular scattering models of elastic electron-neutral collisions for Monte Carlo plasma simulations.
*Plasma Sources Science and Technology*, 31:065013.**2022**. - K. Lee, H. C. Elman, C. E. Powell, and D. Lee.
Enhanced alternating energy minimization methods for stochastic Galerkin matrix equations.
*BIT Numerical Mathematics*, 62:965–994.**2022**. - B. Sousedik, H. C. Elman, K. Lee, and R. Price.
On surrogate learning for linear stability assessment of Navier-Stokes equations with stochastic viscosity.
*Applications of Mathematics*, 67:727–749.**2022**. - C. J. McDevitt and X.-Z. Tang.
Runaway electron current reconstitution after a non-axisymmetric magnetohydrodynamic flush.
*submitted*.**2022**. - Y. Li, B. Srinivasan, Y. Zhang, and X.-Z. Tang.
Bohm criterion of plasma sheaths away from asymptotic limits.
*Physical Review Letters*, 128:085002.**2022**. - Y. Li, B. Srinivasan, Y. Zhang, and X.-Z. Tang.
Transport physics dependence of Bohm speed in presheath–sheath transition.
*Physics of Plasmas*, 29:113509.**2022**. - N. A. Garland, R. Maulik, Q. Tang, X. Z. Tang, and P. Balaprakash.
Efficient data acquisition and training of collisional-radiative model artificial neural network surrogates through adaptive parameter space sampling.
*Machine Learning: Science and Technology*, 3:045003.**2022**. - J. J. Lee, T. Bui-Thanh, U. Villa, and O. Ghattas.
Forward and inverse modeling of fault transmissibility in subsurface flows.
*Computers and Mathematics with Applications*, 128:354–367.**2022**. - A. H. Boozer.
Local analysis of fast magnetic reconnection.
*Physics of Plasmas*, 29:052104.**2022**. - I. Fekete, S. Conde, and J. N. Shadid.
Embedded pairs for optimal explicit strong stability preserving Runge–Kutta methods.
*Journal of Computational and Applied Mathematics*, 412:114325.**2022**. - P. Ohm, T. A. Wiesner, E. C. Cyr, J. J. Hu, J. N. Shadid, and R. S. Tuminaro.
A monolithic algebraic multigrid framework for multiphysics applications with examples from resistive MHD.
*Electronic Transactions on Numerical Analysis*, 55:365–390.**2022**. - A. H. Boozer.
Magnetic field evolution and reconnection in low resistivity plasmas.
*Submitted*.**2022**. - M. M. Crockatt, S. Mabuza, J. N. Shadid, S. Conde, T. M. Smith, and R. P. Pawlowski.
An implicit monolithic AFC stabilization method for the CG finite element discretization of the fully-ionized ideal multifluid electromagnetic plasma system.
*Journal of Computational Physics*, 464.**2022**. - M. G. Yoo, W. X. Wang, E. Startsev, C. H. Ma, S. Ethier, J. Chen, and X. Z. Tang.
The 3D magnetic topology and plasma dynamics in open stochastic magnetic field lines.
*Physics of Plasmas*, 29.**2022**. - T. Bui-Thanh, Q. Li, and L. Zepeda-Nunez.
Bridging and Improving Theoretical and Computational Electric Impedance Tomography via Data Completion.
*SIAM Journal on Scientific Computing*, 44:B668–B693.**2022**. - N. A. Garland, H. K. Chung, M. C. Zammit, C. J. McDevitt, J. Colgan, C. J. Fontes, and X. Z. Tang.
Understanding how minority relativistic electron populations may dominate charge state balance and radiative cooling of a post-thermal quench tokamak plasma.
*Physics of Plasmas*, 29.**2022**. - A. H. Boozer.
The rapid destruction of toroidal magnetic surfaces.
*Physics of Plasmas*, 29.**2022**. - Q. Tang, L. Chacón, T. V. Kolev, J. N. Shadid, and X. Z. Tang.
An adaptive scalable fully implicit algorithm based on stabilized finite element for reduced visco-resistive MHD.
*Journal of Computational Physics*, 454.**2022**. - H. C. Elman, J. Liang, and T. Sánchez-Vizuet.
Surrogate approximation of the Grad–Shafranov free boundary problem via stochastic collocation on sparse grids.
*Journal of Computational Physics*, 448.**2022**.

## 2021

- H. Goh, S. Sheriffdeen, J. Wittmer, T. Bui-Thanh, J. Bruna, J. S. Hesthaven, and L. Zdeborova.
Solving Bayesian Inverse Problems via Variational Autoencoders.
*Proceedings of Machine Learning Research*, 145:386–425.**2021**. - W. Zhang, G. Rossini, T. Bui-Thanh, and M. Sacks.
The integration of structure and high-fidelity material models in heart valve simulations using machine learning, International Journal for Numerical Methods in Biomedical Engineering.
*International Journal for Numerical Methods in Biomedical Engineering*, 37:e3438.**2021**. - H. Nguyen and T. Bui-Thanh.
Model-Constrained Deep Learning Approaches for Inverse Problems.
*submitted*.**2021**. - T. Bui-Thanh.
The Optimality of Bayes' Theorem.
*SIAM News*.**2021**. - N. A. Garland, R. Maulik, Q. Tang, X.-Z. Tang, and P. Balaprakash.
Efficient training of artificial neural network surrogates for a collisional-radiative model through adaptive parameter space sampling.
*Submitted*.**2021**. - S. Liu, Q. Tang, and X. Z. Tang.
A parallel cut-cell algorithm for the free-boundary Grad-Shafranov problem.
*SIAM Journal on Scientific Computing*, 43:B1198–B1225.**2021**. - A. Myers, A. H. Thiéry, K. Wang, and T. Bui-Thanh.
Sequential ensemble transform for Bayesian inverse problems.
*Journal of Computational Physics*, 427.**2021**. - M. G. Yoo, W. X. Wang, E. Startsev, C. H. Ma, S. Ethier, J. Chen, and X. Z. Tang.
Collisionless plasma transport mechanisms in stochastic open magnetic field lines in tokamaks.
*Nuclear Fusion*, 61.**2021**. - S. Kang and T. Bui-Thanh.
A scalable exponential-DG approach for nonlinear conservation laws: With application to Burger and Euler equations.
*Computer Methods in Applied Mechanics and Engineering*, 385.**2021**. - J. Wittmer and T. Bui-Thanh.
Data-Informed Regularization for Inverse and Imaging Problems.
*Handbook of Mathematical Models and Algorithms in Computer Vision and Imaging*, 1–38.**2021**. - B. Zhu, H. Seto, X. qiao Xu, and M. Yagi.
Drift reduced Landau fluid model for magnetized plasma turbulence simulations in BOUT++ framework.
*Computer Physics Communications*, 267.**2021**. - M. Crockatt and J. Shadid.
Development, Implementation, and Verification of Partially-Ionized Collisional Multifluid Plasma Models in Drekar.
*Sandia National Laboratories Technical report*, SAND2021–7427.**2021**. - A. H. Boozer.
The interaction of the ITER first wall with magnetic perturbations.
*Nuclear Fusion*, 61.**2021**. - P. Cagas, A. H. Hakim, and B. Srinivasan.
A boundary value "reservoir problem" and boundary conditions for multi-moment multifluid simulations of sheaths.
*Physics of Plasmas*, 28.**2021**. - N. M. Li, X. Q. Xu, R. J. Goldston, J. Z. Sun, and D. Z. Wang.
Impact of plasma density/collisionality on divertor heat flux width.
*Nuclear Fusion*, 61.**2021**. - J. W. Burby, Q. Tang, and R. Maulik.
Fast neural Poincaré maps for toroidal magnetic fields.
*Plasma Physics and Controlled Fusion*, 63.**2021**. - A. H. Boozer.
Plasma steering to avoid disruptions in ITER and tokamak power plants.
*Nuclear Fusion*, 61.**2021**. - I. Tomas, J. Shadid, M. Crockatt, M. Maier, J.-L. Guermond, and R. Pawlowski.
Final report of activities for the LDRD-express project #223796 titled: “Fluid models of charged species transport: numerical methods with mathematically guaranteed properties”, PI: Ignacio Tomas, Co-PI: John Shadid.
*Sandia National Laboratories Technical report*, SAND2021–11481.**2021**. - J. H. Chaudhry, A. E. Rappaport, and J. N. Shadid.
An a Posteriori error analysis for the equations of stationary incompressible magnetohydrodynamics.
*SIAM Journal on Scientific Computing*, 43:B354–B380.**2021**.

## 2020

- R. Maulik, N. A. Garland, J. W. Burby, X. Z. Tang, and P. Balaprakash.
Neural network representability of fully ionized plasma fluid model closures.
*Physics of Plasmas*, 27.**2020**. - S. Mabuza, J. N. Shadid, E. C. Cyr, R. P. Pawlowski, and D. Kuzmin.
A linearity preserving nodal variation limiting algorithm for continuous Galerkin discretization of ideal MHD equations.
*Journal of Computational Physics*, 410.**2020**. - S. Kang, F. X. Giraldo, and T. Bui-Thanh.
IMEX HDG-DG: A coupled implicit hybridized discontinuous Galerkin and explicit discontinuous Galerkin approach for shallow water systems.
*Journal of Computational Physics*, 401.**2020**. - N. A. Garland, H. K. Chung, C. J. Fontes, M. C. Zammit, J. Colgan, T. Elder, C. J. McDevitt, T. M. Wildey, and X. Z. Tang.
Impact of a minority relativistic electron tail interacting with a thermal plasma containing high-atomic-number impurities.
*Physics of Plasmas*, 27.**2020**. - Z. PENG, Q. TANG, and X. Z. TANG.
An adaptive discontinuous petrov-galerkin method for the grad-shafranov equation.
*SIAM Journal on Scientific Computing*, 42:B1227–B1249.**2020**. - S. Muralikrishnan, T. Bui-Thanh, and J. N. Shadid.
A multilevel approach for trace system in HDG discretizations.
*Journal of Computational Physics*, 407.**2020**. - N. M. Li, X. Q. Xu, J. W. Hughes, J. L. Terry, J. Z. Sun, and D. Z. Wang.
Simulations of divertor heat flux width using transport code with cross-field drifts under the BOUT++ framework.
*AIP Advances*, 10.**2020**. - I. Ambartsumyan, W. Boukaram, T. Bui-Thanh, O. Ghattas, D. Keyes, G. Stadler, G. Turkiyyah, and S. Zampini.
Hierarchical matrix approximations of hessians arising in inverse problems governed by PDEs.
*SIAM Journal on Scientific Computing*, 42:A3397–A3426.**2020**. - L. Wang, X. Q. Xu, B. Zhu, C. Ma, and Y. A. Lei.
Deep learning surrogate model for kinetic Landau-fluid closure with collision.
*AIP Advances*, 10.**2020**. - A. H. Boozer.
Flattening of the tokamak current profile by a fast magnetic reconnection with implications for the solar corona.
*Physics of Plasmas*, 27.**2020**. - C. Ma, B. Zhu, X. Q. Xu, and W. Wang.
Machine learning surrogate models for Landau fluid closure.
*Physics of Plasmas*, 27.**2020**.

## 2019

- H. Goh, S. Sheriffdeen, J. Wittmer, and T. Bui-Thanh.
Solving Bayesian Inverse Problems via Variational Autoencoders.
*Submitted*.**2019**. - S. Sheriffdeen, J. C. Ragusa, J. E. Morel, M. L. Adams, and T. Bui-Thanh.
Accelerating PDE-constrained Inverse Solutions with Deep Learning and Reduced Order Models.
*Submitted*.**2019**. - X. Q. Xu, N. M. Li, Z. Y. Li, B. Chen, T. Y. Xia, T. F. Tang, B. Zhu, and V. S. Chan.
Simulations of tokamak boundary plasma turbulence transport in setting the divertor heat flux width.
*Nuclear Fusion*, 59.**2019**. - Z. Guo, C. McDevitt, and X. Tang.
Toroidal effect on runaway vortex and avalanche growth rate.
*Physics of Plasmas*, 26.**2019**. - N. Alger, V. Rao, A. Myers, T. Bui-Thanh, and O. Ghattas.
Scalable matrix-free adaptive product-convolution approximation for locally translation-invariant operators∗.
*SIAM Journal on Scientific Computing*, 41:A2296–A2328.**2019**. - T. Wildey, S. Muralikrishnan, and T. Bui-Thanh.
Unified geometric multigrid algorithm for hybridized high-order finite element methods.
*SIAM Journal on Scientific Computing*, 41:S172–S195.**2019**. - W. X. Wang, T. S. Hahm, E. A. Startsev, S. Ethier, J. Chen, M. G. Yoo, and C. H. Ma.
Self-driven current generation in turbulent fusion plasmas.
*Nuclear Fusion*, 59.**2019**. - L. Wang, B. Zhu, X. Q. Xu, and B. Li.
A Landau-fluid closure for arbitrary frequency response.
*AIP Advances*, 9.**2019**. - C. J. McDevitt, Z. Guo, and X. Z. Tang.
Spatial transport of runaway electrons in axisymmetric tokamak plasmas.
*Plasma Physics and Controlled Fusion*, 61.**2019**. - C. J. McDevitt and X. Z. Tang.
Runaway electron generation in axisymmetric tokamak geometry.
*EPL*, 127.**2019**. - J. G. Chen, X. Q. Xu, and Y. A. Lei.
Extension of Landau-fluid closure to weakly collisional plasma regime.
*Computer Physics Communications*, 236:128–134.**2019**. - C. J. McDevitt, Z. Guo, and X. Z. Tang.
Avalanche mechanism for runaway electron amplification in a tokamak plasma.
*Plasma Physics and Controlled Fusion*, 61.**2019**. - J. J. Lee, S. J. Shannon, T. Bui-Thanh, and J. N. Shadid.
Analysis of an hdg method for linearized incompressible resistive MHD equations.
*SIAM Journal on Numerical Analysis*, 57:1697–1722.**2019**.

## 2018

- C. J. McDevitt, Z. Guo, and X. Z. Tang.
Relation of the runaway avalanche threshold to momentum space topology.
*Plasma Physics and Controlled Fusion*, 60.**2018**. - Z. Guo, C. J. McDevitt, and X. Z. Tang.
Control of runaway electron energy using externally injected whistler waves.
*Physics of Plasmas*, 25.**2018**.