Novel aspects of plasma control in ITER

Humphreys, D. A.; Ambrosino, G.; Vries, Peter de; Felici, F.; Sh, Kim; Jackson, G.L.; Kallenbach, A.; Kolemen, Egemen; Lister, J.B.; Moreau, D.; Pironti, A.; Raupp, G.; Sauter, O.; Schuster, Eugenio; Snipes, J. A.; Treutterer, W.; Walker, M.L.; Welander, A.S.; Winter, A.; Zabeo, L.

doi:10.1063/1.4907901

Cited by 48 publications

(49 citation statements)

References 72 publications

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“…Major disruptions are global tokamak plasma instabilities which can result from control system failure or from crossing stability boundaries. Although extensive research has been devoted to avoiding disruptions [5,6], it is doubtful that they can be avoided with 100% certainty, motivating the study of rapid shutdown methods to safely dissipate plasma energy in the event of an unavoidable disruption [7,8].…”

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confidence: 99%

Demonstration of Tokamak Discharge Shutdown with Shell Pellet Payload Impurity Dispersal

et al. 2019

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The first rapid tokamak discharge shutdown using dispersive core payload deposition with shell pellets has been achieved in the DIII-D tokamak. Shell pellets are being investigated as a possible new path toward achieving tokamak disruption mitigation with both low conducted wall heat loads and slow current quench. Conventional disruption mitigation injects radiating impurities into the outer edge of the tokamak plasma, which tends to result in poor impurity assimilation and creates a strong edge cooling and outward heat flow, thus requiring undesirable high-Z impurities to achieve low conducted heat loads. The shell pellet technique aims to produce a hollow temperature profile by using a thin, low-ablation shell surrounding a dispersive payload, giving greatly increased impurity ablation (and radiation) rate when the payload is released in the plasma core. This principle was demonstrated successfully using outer diameter = 3.6 mm, thickness = 40 μm diamond shells holding boron powder. The pellets caused rapid (< 10 ms) discharge shutdown with low conducted divertor heat fluence (~0.1 MJ/m 2 ). Confirmation of massive release of the boron powder payload into the plasma core was obtained spectroscopically. Some evidence for the formation of a hollow temperature profile during the shutdown was observed. These first results open a new avenue for disruption mitigation research, hopefully enabling development of highly effective methods of avoiding disruption wall damage in future reactor-scale tokamaks.

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confidence: 99%

Demonstration of Tokamak Discharge Shutdown with Shell Pellet Payload Impurity Dispersal

et al. 2019

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“…In (future) plasma control systems, a profile controller will be interfaced with a supervisory controller that may set controller activation, references and parameters as well as available actuators in real-time based on the plasma state and detected events [51]. The MPC controller's ability to deal with time-varying references, activations and actuator limits encourages to use it in the further development of integrated control strategies involving the management of actuators shared between several control tasks.…”

Section: Discussionmentioning

confidence: 99%

Profile control simulations and experiments on TCV: a controller test environment and results using a model-based predictive controller

et al. 2017

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The successful performance of a model predictive profile controller is demonstrated in simulations and experiments on the TCV tokamak, employing a profile controller test environment. Stable high-performance tokamak operation in hybrid and advanced plasma scenarios requires control over the safety factor profile (q-profile) and kinetic plasma parameters such as the plasma beta. This demands to establish reliable profile control routines in presently operational tokamaks. We present a model predictive profile controller that controls the q-profile and plasma beta using power requests to two clusters of gyrotrons and the plasma current request. The performance of the controller is analyzed in both simulation and TCV L-mode discharges where successful tracking of the estimated inverse q-profile as well as plasma beta is demonstrated under uncertain plasma conditions and the presence of disturbances. The controller exploits the knowledge of the time-varying actuator limits in the actuator input calculation itself such that fast transitions between targets are achieved without overshoot. A software environment is employed to prepare and test this and three other profile controllers in parallel in simulations and experiments on TCV. This set of tools includes the rapid plasma transport simulator RAPTOR and various algorithms to reconstruct the plasma equilibrium and plasma profiles by merging the available measurements with model-based predictions. In this work the estimated q-profile is merely based on RAPTOR model predictions due to the absence of internal current density measurements in TCV. These results encourage to further exploit model predictive profile control in experiments on TCV and other (future) tokamaks.

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“…Other algorithmic science and technology research encompassed by this TEC area include real-time analysis of complex plasma conditions such as the plasma state and MHD stability. Faster-than-Real-Time simulation of the plasma state, coupled with real-time analysis capabilities, is one example identified as a requirement for ITER operation 3,18,19 . to potentially reduce the time and cost of fusion science research for power generation.…”

Section: Advanced Algorithmsmentioning

confidence: 99%

Summary of the FESAC Transformative Enabling Capabilities Panel Report

Maingi

Lumsdaine

Allain

et al. 2019

Fusion Science and Technology

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The US Fusion Energy Sciences Advisory Committee (FESAC) was charged 'to identify the most promising transformative enabling capabilities (TEC) for the U.S. to pursue that could promote efficient advance toward fusion energy, building on burning plasma science and technology.' A subcommittee of U.S. technical experts was formed, and received community input in the form of white papers and presentations on the charge questions. The subcommittee identified four 'most promising transformative enabling capabilities': • Advanced algorithms • High critical temperature superconductors • Advanced materials and manufacturing • Novel technologies for tritium fuel cycle control In addition, one second tier TEC, defined as a 'promising transformative enabling capability' was identified: fast flowing liquid metal plasma facing components. Each of these TECs presents a tremendous opportunity to accelerate fusion science and technology toward power production. Dedicated investment in these TECs for fusion systems is 1 needed to capitalize on the rapid advances being made for a variety of non-fusion applications, to fully realize their transformative potential for fusion energy.

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Novel aspects of plasma control in ITER

Cited by 48 publications

References 72 publications

Demonstration of Tokamak Discharge Shutdown with Shell Pellet Payload Impurity Dispersal

Demonstration of Tokamak Discharge Shutdown with Shell Pellet Payload Impurity Dispersal

Profile control simulations and experiments on TCV: a controller test environment and results using a model-based predictive controller

Summary of the FESAC Transformative Enabling Capabilities Panel Report

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