Article
Physics, Fluids & Plasmas
J. Citrin, S. Maeyama, C. Angioni, N. Bonanomi, C. Bourdelle, F. J. Casson, E. Fable, T. Goerler, P. Mantica, A. Mariani, M. Sertoli, G. Staebler, T. Watanabe
Summary: Previous studies suggested that ETG turbulence could lead to an anti-gyroBohm isotope scaling in JET high-performance hybrid H-mode scenarios. However, a comparison study with higher-fidelity turbulence modeling invalidates this claim and shows that ion-scale turbulence with magnetic field perturbations can match the power balance fluxes within temperature gradient error margins. Multiscale gyrokinetic simulations from two distinct codes also demonstrate the absence of significant ETG heat flux, indicating that simple rules-of-thumb are insufficient criteria for its onset.
Article
Physics, Fluids & Plasmas
B. S. Patel, D. Dickinson, C. M. Roach, H. R. Wilson
Summary: This study analyzed a spherical tokamak plasma equilibrium with a power of 1 GW and identified the dominant micro-instabilities that may occur. A marginally stable state was found at θ(0) = 0.0. This research is important for understanding turbulent transport in high beta STs.
Article
Physics, Fluids & Plasmas
G. Brochard, J. Bao, C. Liu, N. Gorelenkov, G. Choi, G. Dong, P. Liu, J. Mc Clenaghan, J. H. Nicolau, F. Wang, W. H. Wang, X. Wei, W. L. Zhang, W. Heidbrink, J. P. Graves, Z. Lin, H. Lutjens
Summary: Verification and linear validation of the internal kink instability have been performed in tokamak using gyrokinetic and kinetic-MHD codes. The simulations show that kinetic effects and magnetic perturbations strongly affect the growth rate and mode structure of the internal kink instability.
Article
Physics, Fluids & Plasmas
Ehab Hassan, D. R. Hatch, M. R. Halfmoon, M. Curie, M. T. Kotchenreuther, S. M. Mahajan, G. Merlo, R. J. Groebner, A. O. Nelson, A. Diallo
Summary: This study presents a simulation of microtearing mode (MTM) in the H-mode pedestal of an ELMy H-mode DIII-D discharge. The simulations show distinct frequency bands in the magnetic spectrogram, which correspond closely with the MTMs centered at the peak of the omega* profile. The study highlights the importance of global treatment for accurately reproducing the detailed band gaps of the low-n fluctuations.
Article
Physics, Fluids & Plasmas
T. M. Wilks, L. A. Morton, D. M. Kriete, M. Knolker, P. B. Snyder, K. Barada, C. Paz-Soldan, T. Rhodes, K. H. Burrell, X. Chen, J. W. Hughes
Summary: Experiments on the DIII-D tokamak have pushed the operational limits of wide pedestal quiescent H-mode plasmas towards increased ITER relevance by demonstrating well-matched plasma shape and zero injected torque. Wide pedestal QH-modes, with enhanced edge transport generated by turbulence or a limit cycle oscillation, are seen as a promising regime for future power producing devices.
Article
Physics, Fluids & Plasmas
Philipp Ulbl, Thomas Body, Wladimir Zholobenko, Andreas Stegmeir, Jan Pfennig, Frank Jenko
Summary: Understanding and predicting turbulent transport in fusion devices' edge and scrape-off layer is crucial. The latest improvements to the GENE-X turbulence code are validated against experimental results in the TCV tokamak. GENE-X features a full-f electromagnetic gyrokinetic model and can model collisions using either a basic BGK or a more sophisticated LBD collision operator. The accuracy of the collision model significantly improves the match to experimental measurements.
PHYSICS OF PLASMAS
(2023)
Article
Physics, Fluids & Plasmas
M. T. Curie, D. R. Hatch, M. Halfmoon, J. Chen, D. L. Brower, E. Hassan, M. Kotschenreuther, S. M. Mahajan, R. J. Groebner
Summary: In this study, the experimental data on electromagnetic fluctuations in DIII-D was compared with detailed gyrokinetic simulations using GENE. The unique capability of the Faraday-effect radial interferometer-polarimeter (RIP) diagnostic in measuring internal fluctuations of magnetic fields was utilized.
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
G. M. Staebler, E. A. Belli, J. Candy, J. E. Kinsey, H. Dudding, B. Patel
Summary: This paper verifies and calibrates a new quasi-linear transport model based on a large database of gyrokinetic turbulence simulations. The modification of a key parameter in the model is found to be necessary for better fitting temperature and density gradients. The new model shows significantly improved fit in electron and ion energy fluxes compared to previous saturation models, leading to revisions in related models.
Article
Physics, Fluids & Plasmas
T. N. Bernard, F. D. Halpern, M. Francisquez, N. R. Mandell, J. Juno, G. W. Hammett, A. Hakim, G. J. Wilkie, J. Guterl
Summary: This study presents the novel coupling of a continuum full-F gyrokinetic turbulence model with a 6D continuum model for kinetic neutrals using the Gkeyll code. The aim is to improve the understanding of the role of neutrals in plasma fueling, detachment, and their interaction with edge plasma profiles and turbulence statistics.
PHYSICS OF PLASMAS
(2022)
Article
Physics, Fluids & Plasmas
T. Stoltzfus-Dueck, W. A. Hornsby, S. R. Grosshauser
Summary: The study investigates the interaction between ion Landau damping and E X B drift, as well as their impact on momentum flux in turbulence. Nonlinear simulations provide insights into the fraction of fluctuation free energy through ion Landau damping and the variability of symmetry-breaking momentum flux.
PHYSICS OF PLASMAS
(2022)
Article
Physics, Fluids & Plasmas
E. A. Belli, J. Candy, I Sfiligoi
Summary: The transition from ion-scale dominated regimes to multiscale transport regimes that couple ion and electron scales in turbulent transport has been studied using gyrokinetic simulations. It was found that the magnitude of the ion-scale poloidal wavenumber spectrum of the nonlinear turbulent energy flux increases while the magnitude of the high-wavenumber spectrum decreases during the transition. This decrease in electron-scale transport is due to nonlinear mixing with ion-scale fluctuations and ion-scale-driven zonal flows.
PLASMA PHYSICS AND CONTROLLED FUSION
(2023)
Article
Physics, Fluids & Plasmas
Amit K. K. Singh, J. Mahapatra, J. Chowdhury, D. Aggarwal, T. Hayward-Schneider, R. Ganesh, E. Lanti, L. Villard
Summary: In this work, linear and nonlinear collisionless electrostatic simulations were conducted to study the standard and short wavelength ion temperature gradient mode (SWITG) in the ADITYA-U tokamak. The simulations showed the coexistence of the SWITG mode and the standard ion temperature gradient (ITG) mode in ADITYA-U due to steep density and temperature gradients. Good agreement was observed in the growth rate and real frequency values between the linear global eigenvalue gyrokinetic code GLOGYSTO and the nonlinear global gyrokinetic particle-in-cell code ORB5. Linear stability analysis revealed the suppression of SWITGs for low values of R-0/L-T, leaving only the standard ITG mode unstable. Nonlinear simulations confirmed the minimal contribution of SWITG mode to thermal ion heat transport due to the zonal flow shearing effect.
Article
Physics, Fluids & Plasmas
M. R. Halfmoon, D. R. Hatch, M. T. Kotschenreuther, S. M. Mahajan, A. O. Nelson, E. Kolemen, M. Curie, A. Diallo, R. J. Groebner, E. Hassan, E. A. Belli, J. Candy
Summary: Gyrokinetic simulations were used to study pedestal fluctuations in DIII-D discharge 174082, revealing contributions from electron temperature gradient-driven transport and neoclassical transport to electron heat flux. The presence of microtearing modes and MHD modes were found to likely account for the remaining energy losses in the electron and ion channels, respectively. The analysis suggests that both MHD modes and microtearing modes are simultaneously active, with MHD modes primarily affecting particle transport.
PHYSICS OF PLASMAS
(2022)
Article
Physics, Fluids & Plasmas
G. M. Staebler, J. Candy, E. A. Belli, J. E. Kinsey, N. Bonanomi, B. Patel
Summary: The investigation focuses on the properties of 3D saturated fluctuation intensity of electric potential in gyrokinetic turbulence simulations, using linear eigenmodes and geometry shape functions to construct a model for accurate calculation of electron and ion energy flux poloidal wavenumber spectrum. New insights are gained into the way zonal flow mixing saturates ion-scale turbulence by controlling the radial wavenumber width of the turbulence spectrum.
PLASMA PHYSICS AND CONTROLLED FUSION
(2021)
Article
Physics, Fluids & Plasmas
W. Guttenfelder, R. J. Groebner, J. M. Canik, B. A. Grierson, E. A. Belli, J. Candy
Summary: This paper presents linear and nonlinear gyrokinetic analyses in the pedestal region of two DIII-D ELMy H-mode discharges, showing the impact of divertor configurations on pedestal profiles. The study finds that electron temperature gradients are correlated with ETG instability thresholds, leading to significant contributions to electron heat fluxes.
Article
Physics, Fluids & Plasmas
M. W. Brookman, M. E. Austin, C. C. Petty, R. J. La Haye, K. Barada, T. L. Rhodes, Z. Yan, A. Koehn, M. B. Thomas, J. Leddy, R. G. L. Vann
Summary: Microwave heat pulse propagation experiments on the DIII-D tokamak have shown a correlation between millimeter-scale turbulence and broadening of electron cyclotron (EC) wave deposition profiles. Through perturbative analysis of EC power modulation and Fourier harmonics, a linear model can resolve broadening effects in deposition width. The experiments highlight the need for 3D full-wave codes to accurately model fluctuation effects and predict nonlinear behavior in future devices.
PHYSICS OF PLASMAS
(2021)
Article
Instruments & Instrumentation
X. Chen, J. Ruiz Ruiz, N. T. Howard, W. Guttenfelder, J. Candy, J. W. Hughes, R. S. Granetz, A. E. White
Summary: A new pseudolocal tomography algorithm has been developed for soft X-ray imaging measurements of turbulent electron temperature fluctuations in tokamaks and stellarators, overcoming constraints of limited viewing ports and lines of sight. Numerical modeling shows that the turbulence wavenumber spectrum can be reliably reconstructed with an acceptable number of viewing angles and lines of sight, using suitable low SNR detectors. It is feasible to use a SXR imaging diagnostic with a pseudolocal reconstruction algorithm for measuring turbulent delta T-e.
REVIEW OF SCIENTIFIC INSTRUMENTS
(2021)
Article
Physics, Fluids & Plasmas
A. M. Garofalo, S. Ding, W. M. Solomon, B. A. Grierson, X. Jian, T. H. Osborne, C. Holland, M. Knolker, F. M. Laggner, C. Chrystal, A. Marinoni, C. C. Petty
Summary: Analysis of experiments on DIII-D and modeling results show that high plasma toroidal rotation plays a key role in achieving high energy confinement quality, rather than high pedestal. Experimental and modeling results indicate that high rotation shear discharges have high levels of H(98y2), independent of pedestal height, while high pedestal discharges with low rotation shear have levels of H(98y2) only slightly above 1. The toroidal rotation shear, which varies with the level of injected neutral beam torque per particle, mainly determines the energy confinement quality.
Article
Physics, Fluids & Plasmas
K. Ida, R. M. McDermott, C. Holland, M. J. Choi, L. M. Yu, T. Kobayashi, J. M. Kwon, Y. Kosuga
Summary: This conference report summarizes the contributions and discussions at the joint meeting of the 9th Asia Pacific-Transport Working Group (APTWG) & EU-US Transport Task Force (TTF) workshop. The meeting focused on various aspects of transport and physics, including the isotope effect, turbulence spreading and coupling, interplay between magnetohydrodynamic topology/instability and turbulent transport, interaction between energetic particle driven instability and transport, and model reduction and experiments for validation.
Article
Physics, Fluids & Plasmas
S. R. Haskey, Arash Ashourvan, S. Banerjee, K. Barada, E. A. Belli, A. Bortolon, J. Candy, J. Chen, C. Chrystal, B. A. Grierson, R. J. Groebner, F. M. Laggner, M. Knolker, G. J. Kramer, M. R. Major, G. Mckee, G. M. Staebler, Z. Yan, M. A. Van Zeeland
Summary: The power balance of ion heat flux in the pedestal region on DIII-D is found to increase and become increasingly anomalous in experiments with higher temperature and lower density pedestals. Direct measurements of the main-ion temperature are essential in calculating the ion heat flux, as differences between the temperature of D+ and C6+ impurity ions can affect the results. Both neoclassical transport calculations and non-linear gyrokinetic calculations show that turbulent ion heat flux due to ion scale electrostatic turbulence plays a significant role, especially at lower collisionality. Beam emission spectroscopy and Doppler backscattering measurements indicate increased ion-scale fluctuations in the steep gradient region of the H-mode pedestal. These findings suggest that weakly suppressed ion scale electrostatic turbulence is responsible for the observed neoclassical ion heat fluxes and their increases at lower collisionality. These new results provide important insights into plasma heat transport.
PHYSICS OF PLASMAS
(2022)
Article
Physics, Fluids & Plasmas
Hyojong Lee, Hyeonjun Lee, Yoon Seong Han, Jiheon Song, E. A. Belli, Wonho Choe, Jisung Kang, Jekil Lee, J. Candy, Jungpyo Lee
Summary: The theoretical analysis and simulation results in this study reveal that the rotation speed has a certain influence on the tungsten impurity accumulation in KSTAR experiment. Beyond a certain threshold, the rotation reduces the inward convection of impurities or changes it to outward convection, providing a means to control impurity accumulation conditionally. Additionally, the rotation amplifies the temperature screening effect. However, this effect is influenced by the radius and collisionality.
PHYSICS OF PLASMAS
(2022)
Article
Physics, Fluids & Plasmas
X. Jian, C. Holland, S. Ding, M. Knolker, P. B. Snyder, V. S. Chan, A. M. Garofalo, B. Grierson
Summary: The DIII-D super-H mode and its standard counterpart exhibit differences in ion temperature and confinement in the core plasma. The dominance of the ion temperature gradient mode in core transport is found through gyrokinetic and gyrofluid modeling. Flow shear effects significantly impact temperature and confinement in the core.
Article
Physics, Fluids & Plasmas
P. Rodriguez-Fernandez, N. T. Howard, J. Candy
Summary: This study performs multi-channel, nonlinear predictions of core temperature and density profiles for the SPARC tokamak, taking into account both kinetic neoclassical and fully nonlinear gyro-kinetic turbulent fluxes. Through a series of flux-tube, nonlinear, electromagnetic simulations using the CGYRO code with six gyrokinetic species, coupled with a nonlinear optimizer using Gaussian process regression techniques, the simultaneous evolution of energy sources leads to a converged solution in electron temperature, ion temperature, and electron density channels with a minimal number of expensive gyrokinetic simulations without compromising accuracy.
Article
Physics, Fluids & Plasmas
J. E. Kinsey, L. L. Lao, O. Meneghini, J. Candy, P. B. Snyder, G. M. Staebler
Summary: New workflows have been developed to predict magnetohydrodynamic (MHD) equilibrium in tokamak plasmas without measuring the kinetic profiles. The workflows include a cold start tool, an equilibrium solver, and codes for sources and sinks. Validation has been done using a database of DIII-D tokamak discharges, and different workflows have been compared. The predictive equilibrium workflow is expected to have wide applications in experimental planning and reactor studies.
PHYSICS OF PLASMAS
(2022)
Article
Physics, Fluids & Plasmas
J. Ruiz Ruiz, F. Parra, V. H. Hall-Chen, N. Christen, M. Barnes, J. Candy, J. Garcia, C. Giroud, W. Guttenfelder, J. C. Hillesheim, C. Holland, N. T. Howard, Y. Ren, A. E. White
Summary: A study using gyrokinetic simulations and experiments shows that the radial correlation Doppler reflectometry measurements (RCDR) are sensitive to the eddy aspect ratio and the turbulent spectrum. This indicates the potential use of a nonseparable turbulent spectrum to interpret RCDR and other turbulence diagnostics.
PLASMA PHYSICS AND CONTROLLED FUSION
(2022)
Article
Materials Science, Multidisciplinary
D. Kim, J. Kang, M. W. Lee, J. Candy, E. S. Yoon, S. Yi, J. -m. Kwon, Y. -c. Ghim, W. Choe, C. Sung
Summary: Progress in the first gyrokinetic validation study using KSTAR NBI heated L-mode discharge is reported in this paper. The simulated energy flux was under-predicted compared to the experimental energy flux level, and sensitivity to input parameters related to impurity density profile was observed.
CURRENT APPLIED PHYSICS
(2022)
Article
Physics, Fluids & Plasmas
E. A. Belli, J. Candy, I Sfiligoi
Summary: The transition from ion-scale dominated regimes to multiscale transport regimes that couple ion and electron scales in turbulent transport has been studied using gyrokinetic simulations. It was found that the magnitude of the ion-scale poloidal wavenumber spectrum of the nonlinear turbulent energy flux increases while the magnitude of the high-wavenumber spectrum decreases during the transition. This decrease in electron-scale transport is due to nonlinear mixing with ion-scale fluctuations and ion-scale-driven zonal flows.
PLASMA PHYSICS AND CONTROLLED FUSION
(2023)
Article
Physics, Fluids & Plasmas
J. McClenaghan, T. Slendebroek, G. M. Staebler, S. P. Smith, O. M. Meneghini, B. A. Grierson, K. E. Thome, G. Avdeeva, L. L. Lao, J. Candy, W. Guttenfelder
Summary: Investigation on linear gyrokinetic ion-scale modes reveals a transition from ion temperature gradient to microtearing mode (MTM) dominance as density increases in the pedestal region of a parameterized DIII-D sized tokamak. Profiles of H-mode densities, temperatures, and equilibria are parameterized to analyze the linear gyrokinetic ion-scale instabilities using CGYRO. The critical n(MTM) scales with plasma current and can be reduced by increasing the minor radius and major radius. However, the relationship between n(MTM) and density limit physics remains unclear.
PHYSICS OF PLASMAS
(2023)
Article
Physics, Fluids & Plasmas
T. Slendebroek, J. McClenaghan, O. M. Meneghini, B. C. Lyons, S. P. Smith, T. F. Neiser, N. Shi, J. Candy
Summary: We have developed a workflow called Stability, Transport, Equilibrium, and Pedestal (STEP)-zero-dimensional (0D) within the OMFIT integrated modeling framework. The workflow has been validated and shown to accurately predict the energy confinement time in tokamaks. It also has potential in predicting plasmas for proposed fusion reactors, providing a path towards a new fusion power plant design workflow.
PHYSICS OF PLASMAS
(2023)
