Present Position
PSFC Theory Group and PSFC Magnetic Fusion Energy Collaboration/DIII-D Facility
MIT Plasma Science and Fusion Center
Interests
Theory, simulation, and experiments to develop magnetic fusion as a viable energy source. Much of my work focuses on turbulent transport in tokamak fusion plasmas and experiments developing new operating scenarios for future machines.
I frequently present invited papers at international conferences, to audiences ranging from 100 to 700 scientists (27 to date), over 100 refereed publications.
Email: dernst@psfc.mit.edu
Website: https://sites.mit.edu/darinernst
Phone: 617.253.0478
Bio
Education
| 1997 | Ph.D. Physics Massachusetts Institute of Technology 1998 APS Rosenbluth Award for Outstanding Doctoral Thesis in Plasma Physics |
| 1994 – 1995 | Exchange Scholar, Graduate Physics Princeton University |
| 1988 | B.S. Electrical Engineering, completing additional Majors in Mathematics and Physics University of Wisconsin-Madison Chancellor’s Men’s Honorary, 4 years, 30 members campus-wide |
Experience
| 2002 – present | Scientist, MIT Plasma Science and Fusion Center Theory Group and MFE/DIII-D Collaboration |
| 1998 – 2001 | Associate Research Physicist, Princeton Plasma Physics Laboratory |
| 1997 – 1998 | Research Associate, Princeton Plasma Physics Laboratory |
Research
My research focuses on large scale parallel gyrokinetic simulations of plasma microturbulence, analytic theory, and code development. I perform direct comparisons with experiments, using synthetic diagnostics for gyrokinetic codes, including full-wave simulations of microwave fluctuation diagnostics. I do fundamental theory, such as develop and implement the first ever gyrokinetic exact Landau collision operator (recently released in the gyrokinetic code GENE 3.0). I also develop neoclassical pedestal codes and reduced models of multiscale turbulence spanning electron and ion scales. I have led experiments on the MIT Alcator C-Mod tokamak (now ended) and on the General Atomics DIII-D tokamak, the largest U.S. magnetic fusion facility — (14) DIII-D experiments to date. I am actively involved in the DIII-D program and travel to San Diego often. Much of my work focuses on developing advanced operating regimes where turbulence regulates the edge, with the benefit of improved confinement, no ELMs to erode the divertor, reduced divertor heat loads, and promising compatibility with future burning plasmas.
I supervise postdoctoral researchers as the MIT Principal Investigator for the DOE SciDAC Partnership for Multiscale Gyrokinetic Turbulence, collaborating with leading gyrokinetic turbulence theorists and code developers around the world, as well as the FASTMath SciDAC Institute on multiscale numerical algorithms.
- Overall coordinator, U.S. Dept. of Energy Office of Fusion Energy Sciences 2022 National Joint Research Target, “Intrinsically Non-ELMing Enhanced Confinement Regimes”, with 45 researchers from institutions around the U.S. involved in 5 working groups (co-led three of the working groups).
- Co-led the experimental Thrust area, “Develop Non-ELMing High Performance Regimes” in the DIII-D National Fusion program, based at General Atomics in San Diego, with 9 run-days and 13 experiments allocated 2022-2023.
- Co-developed and co-managed the MIT PSFC parallel supercomputing cluster (100 users). Developed analysis and simulation software used by other researchers (>50 users). Received MIT Infinite Mile Award for Outstanding Achievement, Issued by MIT Offices of the Dean for Graduate Education, Provost, and Vice President for Research, for work on the PSFC parallel clusters (2013).
- Lately doing new global simulations of both collisional and turbulent transport in the plasma edge region, which is extremely important, but little understood.
Featured
Our exact GK operator was released Dec. 11, 2023 in GENE-3.0 for general use, making it the only gyrokinetic code with an exact Landau operator including finite gyroradius effects.
Importance of gyrokinetic exact Fokker-Planck collisions in fusion plasma turbulence
Gyrokinetic simulations of turbulence are fundamental to understanding and predicting particle and energy loss in magnetic fusion devices. Previous works have used model collision operators with approximate field-particle terms of unknown accuracy and/or have neglected collisional finite Larmor radius effects. This work moves beyond models to demonstrate important corrections using a gyrokinetic Fokker-Planck collision operator with the exact field-particle terms, in realistic simulations of turbulence in magnetically confined fusion plasmas. The exact operator shows significant corrections for temperature-gradient-driven trapped electron mode turbulence and zonal flow damping, and for microtearing modes in a Joint European Torus pedestal under ITER-like wall conditions. Analysis of the corrections using parameter scans motivates an accurate model which closely reproduces the exact results while reducing computational demands.
Q. Pan, D. R. Ernst and D. Hatch, Phys. Rev. E Letters, 103 L051202 (2021).
Results of the 2022 U.S. Joint Research Target on Intrinsically Non-ELMing Enhanced Confinement Regimes
The 2022 U. S. Joint Research Target focused the efforts of 45 researchers in 5 working groups to carry out extensive simulations and new experiments to advance stable, high performance confinement regimes without edge localized mode transients, which would cause too much material erosion in burning plasmas. These are advanced operating regimes which have multiple advantages, including favorable confinement scalings, reduced divertor heat loads, and promising compatibility with future burning plasmas.
Invited overviews of the results were presented at the 2023 European Physical Society Conference on Plasma Physics, and at the 2023 American Physical Society Division of Plasma Physics Meeting. The 2022 JRT Final Report was submitted and will be released by DOE (165 pages & 100 figures).
D. R. Ernst, A. Bortolon, Xi Chen, J. King, A. O. Nelson, D. Battaglia, A. Hubbard and the 2022 U.S. Joint Research Target Working Groups
Recent Paper published:
D. R. Ernst, A. Bortolon, C. S. Chang, S. Ku, F. Scotti, D. Truong, H. Q. Wang, J. Watkins, Z. Yan, J. Chen, C. Chrystal, F. Glass, R. Hager, S. Haskey, F. Laggner, Z. Li, G. R. McKee and T. L. Rhodes, Broadening of the divertor heat flux profile in high confinement tokamak fusion plasmas with edge pedestals limited by turbulence in DIII-D, Physical Review Letters 132, 235102 (2024).
Video of APS-DPP ITER oral talk:
D. R. Ernst et al., UO06:12: ITER-Relevant Turbulence Broadening of the Divertor Heat Flux Width in DIII-D Quiescent H-Mode Plasmas Featuring Turbulence-Limited Pedestals, MFE: Research in Support of ITER, 66th Annual Meeting of the APS Division of Plasma Physics, October 28-November 1, 2024.
Reduced Model for Interacting Toroidal Ion and Electron Scale Temperature Gradient Driven Turbulence
Electron scale turbulence is important in the plasma core and in the pedestal, where it can account for 30% of the electron heat loss. Direct multiscale simulations show that electron turbulence has an unexpectedly large impact on ion scales, but these simulations require tens of millions of CPU core-hours. In the Partnership for Multiscale Gyrokinetic Turbulence, in collaboration with our FASTMath partners, we developed and implemented multi-rate additive Runge-Kutta methods to periodically sub-cycle electron scale simulations. We have formulated and implemented a reduced toroidal multiscale gyrofluid model, retaining full FLR effects via Bessel functions, using a modified field equation with appropriate electron response at ion and electron scales. The 2D MuSHrooM code closely matches GENE 2D single scale toroidal linear and nonlinear ITG simulations over a wide range of temperature gradients. Using the reduced model, multi-scale toroidal ITG/ETG simulations have been completed in 50 to 100 times less CPU time than 3D gyrokinetic simulations, i.e, with resources characteristic of single scale 3D ITG gyrokinetic turbulence simulations.
M. Francisquez, D. R. Ernst, D. Reynolds and C. Balos, “A 2D gyrofluid model for multiscale turbulence and its comparison to gyrokinetics,” 63rd Annual Meeting of the APS Division of Plasma Physics, November 8-12, 2021.
D. R. Ernst, M. Francisquez, D. Reynolds, C. Balos and C. Woodward, “Reduced model and algorithmic test-bed for cross-scale interactions in multi-scale ITG/ETG turbulence,” 2022 International Sherwood Fusion Theory Conference, Santa Rosa, April 4-6, 2022.
Ian Gill, Darin Ernst, Dan Reynolds, Manaure Francisquez, Cody Balos , Carol Woodward, Progress in Speeding Up Multiscale Simulations of Coupled Toroidal ITG/ETG Turbulence, CP12:106, 66th Annual Meeting of the APS Division of Plasma Physics, October 28-November 1, 2024.
