Multi-scale transport in the DIII-D ITER baseline scenario with direct electron heating and projection to ITER

Grierson, B. A.; Staebler, G. M.; Solomon, W. M.; McKee, G. R.; Holland, C.; Austin, M. E.; Marinoni, A.; Schmitz, L.; Pinsker, R. I.; Team, Diii-D

doi:10.1063/1.5011387

Cited by 23 publications

(27 citation statements)

References 33 publications

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“…Examination of figure 16( a – d ) shows that the predicted energy transport in UCR-P is almost completely electrostatic at all four radii considered, consistent with its relatively moderate value of and previous examinations of predicted transport for other inductive burning plasma scenarios (Grierson et al. 2018; Mantica et al. 2020; Howard et al.…”

Section: Core Transportsupporting

confidence: 82%

“…As seen in figure 19( a ), the UCR-P gyroBohm-normalized ion energy flux is roughly five times larger than the corresponding ITER baseline scenario and SPARC PRD values, and a full order of magnitude larger than two DIII-D H-mode plasmas with varied mixes of NBI and electron cyclotron heating (ECH) performed in an ITER baseline-like (IBS) shape (Grierson et al. 2018). However, the UCR-P normalized electron energy flux is comparable to the normalized ITER value, as well as the DIII-D H-mode with ECH heating.…”

Section: Core Transportmentioning

confidence: 93%

“…Past studies of burning and non-burning plasmas (Fable, Angioni & Sauter 2009; Grierson et al. 2018; Fable et al. 2019; Mantica et al.…”

Section: Core Transportmentioning

confidence: 99%

“…(2020), the DIII-D ITER baseline profiles from Grierson et al. (2018), and the DIII-D L-mode profiles from White et al. (2008) and Holland et al.…”

Section: Core Transportmentioning

confidence: 99%

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Development of compact tokamak fusion reactor use cases to inform future transport studies

Holland,

Bass,

Orlov

et al. 2023

J. Plasma Phys.

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The OMFIT STEP (Meneghini et al., Nucl. Fusion, vol. 10, 2020, p. 1088) workflow has been used to develop inductive and steady-state H-mode core plasma scenario use cases for a $B_0 = 8 \, {\rm T}$ , $R_0 = 4 \, {\rm m}$ machine to help guide and inform future higher-fidelity studies of core transport and confinement in compact tokamak reactors. Both use cases are designed to produce 200 MW or more of net electric power in an up-down symmetric plasma with minor radius $a = 1.4 \, {\rm m}$ , elongation $\kappa = 2.0$ , triangularity $\delta = 0.5$ and effective charge $Z_{{\rm eff}} \simeq 2$ . Additional considerations based on the need for compatibility of the core with reactor-relevant power exhaust solutions and external actuators were used to guide and constrain the use case development. An extensive characterization of core transport in both scenarios is presented, the most important feature of which is the extreme sensitivity of the results to the quantitative stiffness level of the transport model used as well as the predicted critical gradients. This sensitivity is shown to arise from different levels of transport stiffness exhibited by the models, combined with the gyroBohm-normalized fluxes of the predictions being an order of magnitude larger than other H-mode plasmas. Additionally, it is shown that although heating in both plasmas is predominantly to the electrons and collisionality is low, the plasmas remain sufficiently well coupled for the ions to carry a significant fraction of the thermal transport. As neoclassical transport is negligible in these conditions, this situation inherently requires long-wavelength ion gyroradius-scale turbulence to be the dominant transport mechanism in both plasmas. These results are combined with other basic considerations to propose a simple heuristic model of transport in reactor-relevant plasmas, along with simple metrics to quantify coupling and core transport properties across burning and non-burning plasmas.

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Section: Core Transportsupporting

confidence: 82%

Section: Core Transportmentioning

confidence: 93%

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Development of compact tokamak fusion reactor use cases to inform future transport studies

Holland,

Bass,

Orlov

et al. 2023

J. Plasma Phys.

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“…Burning plasmas self-heat through the collisional slowing down of MeV alpha particles, and at this high energy the dominant heat deposition is to the electrons, modifying the plasma turbulent transport properties [315][316][317][318][319][320] . DIII-D has long been equipped with ≈ 3 MW of ECH power (P ECH ) to mimic this heating channel, though this is a small fraction of the available NBI power (≈ 16 MW).…”

Section: A Boundaries and Performance Towards Dominant Electron Heatingmentioning

confidence: 99%

Plasma Performance and Operational Space without ELMs in DIII-D

Paz-Soldan

2020

Preprint

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A database of DIII-D plasmas without edge-localized modes (ELMs) compares the operating space and plasma performance of stationary no-ELM regimes found in conventional tokamaks: ELM suppression with resonant magnetic perturbations (RMPs), quiescent H-mode (QH, including wide-pedestal variant), improved confinement mode (I-mode), enhanced D-alpha H-mode (EDA-H), conventional L-mode, and negative triangularity L-mode (Neg-D). Operational space is documented in terms of engineering and physics parameters, revealing divergent constraints for each regime. Some operational space discriminants (such as pedestal collisionality) are well known, while others, such as low torque & safety factor, or high power & density, are less commonly emphasized. Normalized performance (confinement quality and normalized pressure) also discriminate the no-ELM regimes and favor the regimes tolerant to power in DIII-D: RMP, QH, and Neg-D. Absolute performance (volume-averaged pressure p , confinement time τ , and triple product p τ ) also discriminates no-ELM regimes and is found to rise linearly with IaB (a metric for the magnetic configuration strength, the product of current I, minor radius a, and field B that has units of force), and also benefits from tolerance to power. The highest normalized performance using the metric p τ /IaB is found in QH and RMP regimes. Focusing on ITER-shaped no-ELM plasmas, Q=10 at 15 MA scaled global performance is met with two out of four considered metrics, but only thus far at high torque. Though comparable QH and RMP performance is found, the pedestal pressure (p ped ) is very different. p ped in RMP plasmas is relatively low, and the best performance is found with a high core p fraction alongside high core rotation, consistent with an ExB shear confinement enhancement. p ped of QH plasmas is significantly higher than RMP, and QH performance does not correlate with core rotation. However, the highest QH p ped are found with high carbon fraction. While normalized performance of Neg-D plasmas is comparable to QH and RMP plasmas, the absolute confinement of Neg-D is lower, owing to low elongation and low p ped achieved thus far. Considering integration with electron cyclotron heating (ECH), the operational space for RMP and QH plasmas narrow, while that for EDA-H plasmas open, and the high p ped / p regimes (EDA-H and QH) preserve the highest performance. Only the EDA-H, Neg-D, and L-mode scenarios have approached divertor-compatible high separatrix density conditions, with Neg-D preserving the highest performance owing to its compatibility with both high power and density. Comparison to highlighted ELMing plasmas finds a clearer pedestal correlation to plasma performance, but also reveals that the peak performance of plasmas without ELMs is significantly lower in DIII-D, owing to limits in operational space accessed so far without ELMs.

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Propagation of input parameter uncertainties in transport models

et al. 2018

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The many sources of uncertainty in validation studies of plasma turbulence in magnetically confined fusion devices are well-known. In this paper, we investigate how to efficiently transform uncertainties in experimentally derived transport model inputs into model prediction uncertainties, using the quasilinear trapped-gyro-Landau-fluid (TGLF) turbulent transport model [Staebler et al., Phys. Plasmas 14, 055909 (2007)]. We use the rapidly converging and computationally inexpensive non-intrusive probabilistic collocation method (PCM) to propagate input parameter uncertainty probability distribution functions (PDFs) through TGLF, yielding PDFs of predicted transport fluxes. We observe in many cases that the flux PDFs exhibit significant non-normal features such as strong skewness, even when the input distributions were normal. To illustrate the utility of the PCM approach, we apply this methodology to transport predictions for a DIII-D ITER baseline plasma [Grierson et al., Phys. Plasmas 25, 022509 (2018)] in which the mix of neutral beam injection (NBI) and electron cyclotron heating (ECH) was varied. The model predictions show clear changes in the parametric dependencies and sensitivities of the turbulence between the two heating mixes. Specifically, when only NBI heating was used, the transport fluxes responded significantly only to the ion temperature gradient scale length. However, when both NBI and ECH were applied, the electron transport channels demonstrate a strong sensitivity to the electron temperature and density gradients not observed in the NBI-only case. Additional context for the PCM approach is provided by comparing its predictions with those obtained via a local flux-matching approach. A new set of validation metrics based on the Wasserstein distance is proposed for PDF-based comparisons.

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Multi-scale transport in the DIII-D ITER baseline scenario with direct electron heating and projection to ITER

Cited by 23 publications

References 33 publications

Development of compact tokamak fusion reactor use cases to inform future transport studies

Development of compact tokamak fusion reactor use cases to inform future transport studies

Plasma Performance and Operational Space without ELMs in DIII-D

Propagation of input parameter uncertainties in transport models

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