Koenders, J.T.W.

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 Towards model-based control of divertor detachmentCitation for published version (APA):Koenders, J. T. W. (2021). Towards model-based control of divertor detachment. Abstract from BeneluxWorkshop on Systems and Control 2021, Rotterdam, Netherlands.Document status and date:Published: 01/01/2021Document Version:Accepted manuscript including changes made at the peer-review stagePlease check the document version of this publication:• A submitted manuscript is the version of the article upon submission and before peer-review. There can beimportant differences between the submitted version and the official published version of record. Peopleinterested in the research are advised to contact the author for the final version of the publication, or visit theDOI to the publisher's website.• The final author version and the galley proof are versions of the publication after peer review.• The final published version features the final layout of the paper including the volume, issue and pagenumbers.Link to publicationGeneral rightsCopyright and moral rights for the publications made accessible in the public portal are retained by the authors and/or other copyright ownersand it is a condition of accessing publications that users recognise and abide by the legal requirements associated with these rights.            • Users may download and print one copy of any publication from the public portal for the purpose of private study or research.            • You may not further distribute the material or use it for any profit-making activity or commercial gain            • You may freely distribute the URL identifying the publication in the public portal.If the publication is distributed under the terms of Article 25fa of the Dutch Copyright Act, indicated by the “Taverne” license above, pleasefollow below link for the End User Agreement:www.tue.nl/taverneTake down policyIf you believe that this document breaches copyright please contact us at:openaccess@tue.nlproviding details and we will investigate your claim.Download date: 05. Oct. 2023Towards model-based control of divertor detachmentJ.T.W. Koenders1,21 Energy Systems and Control Group, DIFFER, Eindhoven, the Netherlands2 Control Systems Technology Group, Eindhoven University of Technology, Eindhoven, the NetherlandsJ.T.W.Koenders@differ.nl1 IntroductionThe heat and particle exhaust in tokamaks, the leading reac-tor design for economically viable clean energy productionthrough thermonuclear fusion, is guided to a dedicated re-gion called the divertor. Here, the plasma interacts with thedivertor surface material causing erosion and hence impuri-ties to enter the plasma. Unmitigated, the expected powerfluxes impacting the divertor target during reactor opera-tions exceed present-day engineering limits [1]. Real-timefeedback control of plasma detachment, a regime character-ized by a large reduction of plasma temperature and pres-sure at the divertor target, is required to obtain and maintainlow target fluxes. A systematic approach to achieve this re-duction was recently developed and experimentally demon-strated [2] on the Tokamak à Configuration Variable (TCV)at the EPFL [3]. This approach uses dedicated system iden-tification experiments for controller design enabling controlof the CIII emission front position, which is related to a rel-atively low temperature (<10 eV) region along the divertorleg [4]. We aid controller design by investigating the sys-tem identification results and extracting a dominant physicalprocess. This is the first step to obtain a scalable control-oriented model of the CIII emission front position based onphysical parameters.2 MethodThe control problem can be reduced to an input: fueling ofdeuterium molecules by a gas valve Γpuff [#/s], and an out-put: the CIII emission front location Lpol [m]. Real-time(800 Hz) tracking of the CIII emission front was imple-mented using a detection algorithm [5] applied to spectrallyfiltered images originating from the multi-spectral imagingdiagnostic MANTIS [6]. Figure 1 shows the MANTIS cam-era view, a visual representation of the detection algorithmand the definition of the parameter Lpol. The gas valve islocated at the bottom of the machine. System identificationexperiments were performed by injection of a multisine per-turbation on the input Γpuff and measuring Lpol. Due to thelow signal to noise ratio environment it was chosen to excitethree to six frequencies per experiment. Additionally the gasvalve system limits the frequencies to <50 Hz. Extraction ofa physical process was done by fitting first-principle physicsmodels on the obtained FRF measurements. Steady-statebehavior of the system was estimated using the establishedtime-independent equilibrium code SOLPS-ITER.Figure 1: (a) MANTIS camera view in the TCV Tokamak [6].(b) Identified CIII front location by the detection algo-rithm, indicated by the red X [5]. (c) Geometric repre-sentation of the front location Lpol along the outer leg.3 Results and DiscussionThe identification experiments show phase behavior remi-niscent of a diffusive system, we find a 1D diffusion dom-inated transport model to accurately describe the obtainedFRF measurements. We present a novel control-orientedgrey-box model describing the dynamics of input Γpuff tooutput Lpol. The model accurately reproduces experimentalobservations and can be used for controller design within theidentified operating regime.The underlying physics responsible for the diffusive like be-havior is to be investigated, we hypothesize the process isdominated by plasma-neutral interactions the injected deu-terium molecules undergo until they are ionised.4 AcknowledgmentsThe author thanks Marco de Baar, Matthijs van Berkel, BasilDuval, Olivier Février, Cristian Galperti, Ricky van Kam-pen, Artur Perek, Timo Ravensbergen, Christian Theiler, theTCV Team, and the EUROfusion MST1 team.References[1] R. Pitts et al., Nucl. Mat. Ener. 20, (2019)[2] T. Ravensbergen et al., Nat. Commun. 12, (2021)[3] S. Coda et al., Nucl. Fusion 59, (2019)[4] C. Theiler et al., Nucl. Fusion 57, (2017)[5] T. Ravensbergen et al., Nucl. Fusion 60, (2020)[6] A. Perek et al., Rev. Sci. Instrum. 90, (2019)

Towards model-based control of divertor detachment

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Towards model-based control of divertor detachment

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