The snowflake divertor

Ryutov, D. D.; Soukhanovskii, V.

doi:10.1063/1.4935115

Cited by 68 publications

(85 citation statements)

References 93 publications

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“…Diverted configurations could significantly reduce the interaction of the resulting divertor plasma with nearby components due to the strike points being situated at much longer distances from the evolving hot and dense plasma. 52,53…”

Section: Discussionmentioning

confidence: 99%

Comprehensive 3-D simulation and performance of ITER plasma facing and nearby components during transient events—Serious design issues

Sizyuk

Hassanein

2018

Physics of Plasmas

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A key obstacle to a successful magnetic fusion energy production in Tokamak reactors is performance during abnormal events. Abnormal events include plasma disruptions, edge-localized modes (ELMs), vertical displacement events, and runaway electrons. While tremendous efforts are being made to find ways to mitigate such events, a credible reactor design must be able to tolerate a few of these transient events. We have recently enhanced our comprehensive HEIGHTS (High Energy Interaction with General Heterogeneous Target Systems) simulation package to enable detailed 3-D investigation of the overall aspects of plasma-material interaction processes during all the transient events. Advanced models and numerical tools were developed to efficiently couple major key processes during the transient events, and in particular disruptions and giant ELMs. These include dynamic interaction, deposition, and scattering of the escaping core plasma particles with the evolving and propagating secondary divertor vapor/plasma in the strong magnetic field. These details are critical for assessing the damage to all interior components, including the hidden structure and the first wall which were not directly exposed to these transient events and never thought to be affected as a result. Despite developing numerous efficient numerical techniques and solution methods, such calculations take several months on current supercomputers to complete. Our present results show, for the first time, that unmitigated transient events could cause significant melting and vaporization damage to most interior and hidden components, including the first wall that were not directly exposed to these events. The current ITER divertor design may not work properly and need to be significantly modified or redesigned to prevent this damage. Published by AIP Publishing. https://doi.

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Section: Discussionmentioning

confidence: 99%

Comprehensive 3-D simulation and performance of ITER plasma facing and nearby components during transient events—Serious design issues

Sizyuk

Hassanein

2018

Physics of Plasmas

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“…The control law as formulated in (20) and (21) requires that a matrix of feedback control gains K be computed which converts a vector of state errors to a vector of coil voltage commands. For this purpose, we employ a common technique in control system design known as the linear quadratic regulator (LQR).…”

Section: Lqr Optimal Control Designmentioning

confidence: 99%

Design and simulation of the snowflake divertor control for NSTX–U

Vail

Boyer

Welander

et al. 2019

Plasma Phys. Control. Fusion

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This paper presents the development of a physics-based multiple-input-multiple-output algorithm for real-time feedback control of snowflake divertor (SFD) configurations on the National Spherical Torus eXperiment Upgrade (NSTX-U). A model of the SFD configuration response to applied voltages on the divertor control coils is first derived and then used, in conjunction with multivariable control synthesis techniques, to design an optimal state feedback controller for the configuration. To demonstrate the capabilities of the controller, a nonlinear simulator for axisymmetric shape control was developed for NSTX-U which simultaneously evolves the currents in poloidal field coils based upon a set of feedback-computed voltage commands, calculates the induced currents in passive conducting structures, and updates the plasma equilibrium by solving the free-boundary Grad-Shafranov problem. Closed-loop simulations demonstrate that the algorithm enables controlled operations in a variety of SFD configurations and provides capabilities for accurate tracking of time-dependent target trajectories for the divertor geometry. In particular, simulation results suggest that a time-varying controller which can properly account for the evolving SFD dynamical response is not only desirable but necessary for achieving acceptable control performance. The algorithm presented in this paper has been implemented in the NSTX-U Plasma Control System in preparation for future control and divertor physics experiments.

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“…These options refer to a family of divertor configurations, including super-X [5], snowflake [6], and long leg [7]. They have been explored within the EUROfusion DTT1 project [8] by expansion around the extant baseline to confirm that the configurations could be achieved.…”

Section: Advanced Magnetic Configurations (Amc)mentioning

confidence: 99%

Exploring a broad spectrum of design options for DEMO

Kemp

Wenninger²,

Federici³

et al. 2018

Fusion Engineering and Design

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In the pursuit of realistically achievable design options for demonstrating fusion electricity generation and tritium self-sufficiency in a device to follow ITER, it is vital to explore as fully as possible the available design space and technology options which might lead to a fusion power plant within the timescales envisioned by the EU Roadmap to Fusion Energy. The usual tool for exploring this space is a systems code, such as PROCESS, which seeks to model all important plant systems and physics to provide an integrated power plant design point. However, currently many of these models are tied to assumptions of ITER-like technology and therefore tend to lead to ITER-like plant solutions. This contribution describes a broader set of plant configurations being considered alongside the main baseline design, investigating the impacts on design and costs of designing for (1) flexi-pulsed-steady-state operation, (2) double-null divertors, and (3) the use of high-temperature superconductors. The focus of the work presented here, however, is on (4) advanced magnetic configurations such as snowflake and super-X divertors. We discuss the modifications necessary for the systems code to simulate these configurations and their performance, particularly the divertor geometry and power handling capability; rapid engineering analysis of TF and PF coil positions which can achieve both the required equilibrium and remote-handling access; and initial wider analysis of the physics, neutronics, and other considerations. The reductions in wall area available for breeding tritium affect the choice of blanket technology, and remote handling considerations have a strong impact on the configurations which can be considered reasonable from an engineering and availability perspective. The benefits, disadvantages, risks, and power plant relevance of each configuration over the baseline DEMO design are discussed.

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The snowflake divertor

Cited by 68 publications

References 93 publications

Comprehensive 3-D simulation and performance of ITER plasma facing and nearby components during transient events—Serious design issues

Comprehensive 3-D simulation and performance of ITER plasma facing and nearby components during transient events—Serious design issues

Design and simulation of the snowflake divertor control for NSTX–U

Exploring a broad spectrum of design options for DEMO

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