An overview of the STEP divertor design and the simple models driving the plasma exhaust scenario
This paper presents a comprehensive overview of the preliminary divertor design and plasma exhaust scenario for the reactor-class Spherical Tokamak for Energy Production project. Due to the smaller size of the machine, with a major radius less than half that of most DEMO concepts, the current design...
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2024-01-01
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| Online Access: | https://doi.org/10.1088/1741-4326/ad93e7 |
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| author | S.S. Henderson R.T. Osawa S.L. Newton D. Moulton L. Xiang R. Futtersack M. Kryjak C. Ridgers J. Karhunen A. Jarvinen A. Hudoba S. Bakes F. Eriksson H. Meyer M. Lord A. Tarazona A. Cureton A. Barth B. Chuilon T. Hebrard S. Wang Z. Vizvary D. Vaccaro F. Perez Smith J. Farrington J. Harrison B. Dudson B. Lipschultz |
| author_facet | S.S. Henderson R.T. Osawa S.L. Newton D. Moulton L. Xiang R. Futtersack M. Kryjak C. Ridgers J. Karhunen A. Jarvinen A. Hudoba S. Bakes F. Eriksson H. Meyer M. Lord A. Tarazona A. Cureton A. Barth B. Chuilon T. Hebrard S. Wang Z. Vizvary D. Vaccaro F. Perez Smith J. Farrington J. Harrison B. Dudson B. Lipschultz |
| author_sort | S.S. Henderson |
| collection | DOAJ |
| description | This paper presents a comprehensive overview of the preliminary divertor design and plasma exhaust scenario for the reactor-class Spherical Tokamak for Energy Production project. Due to the smaller size of the machine, with a major radius less than half that of most DEMO concepts, the current design features a double-null divertor geometry, comprising tightly baffled extended outer legs and shorter inner legs approaching an X-divertor. Leveraging a significant database of SOLPS-ITER simulations, the exhaust operational space is mapped out, offering valuable insights into the plasma exhaust dynamics. An approach involving the validation of simple, yet robust models capable of accurately predicting key exhaust parameters is detailed, thereby streamlining the design process. The simple models are used to simulate the entire plasma scenario from the plasma current ramp-up, through the burning phase, to the plasma current ramp-down. Notably, the findings suggest that pronounced detachment, with peak heat loads below engineering limits and electron temperatures below 5 eV, is achievable with a divertor neutral pressure between 10 Pa and 15 Pa during the burning phase, and pressures below 5 Pa during the ramp-up to maximise the auxiliary current-drive efficiency. Throughout the scenario, an Ar concentration of ${\approx}3$ % in the scrape-off layer (SOL) is required, in combination with a core radiation fraction of 70% driven by intrinsic emission and extrinsic injection of Xe seeded fuelling pellets. However, significant uncertainties remain regarding key parameters such as the SOL heat flux width, Ar screening, and plasma kinetic effects. |
| format | Article |
| id | doaj-art-5f49fc0667e24754a51002d97e02fcff |
| institution | OA Journals |
| issn | 0029-5515 |
| language | English |
| publishDate | 2024-01-01 |
| publisher | IOP Publishing |
| record_format | Article |
| series | Nuclear Fusion |
| spelling | doaj-art-5f49fc0667e24754a51002d97e02fcff2025-08-20T01:54:25ZengIOP PublishingNuclear Fusion0029-55152024-01-0165101603310.1088/1741-4326/ad93e7An overview of the STEP divertor design and the simple models driving the plasma exhaust scenarioS.S. Henderson0https://orcid.org/0000-0002-8886-1256R.T. Osawa1S.L. Newton2D. Moulton3L. Xiang4https://orcid.org/0000-0001-8175-6640R. Futtersack5M. Kryjak6C. Ridgers7https://orcid.org/0000-0002-4078-0887J. Karhunen8https://orcid.org/0000-0002-4525-8158A. Jarvinen9A. Hudoba10S. Bakes11F. Eriksson12H. Meyer13https://orcid.org/0000-0002-5565-1199M. Lord14A. Tarazona15A. Cureton16A. Barth17B. Chuilon18T. Hebrard19S. Wang20Z. Vizvary21D. Vaccaro22https://orcid.org/0009-0007-2171-794XF. Perez Smith23https://orcid.org/0009-0001-2218-7203J. Farrington24J. Harrison25https://orcid.org/0000-0003-2906-5097B. Dudson26B. Lipschultz27https://orcid.org/0000-0001-5968-3684United Kingdom Atomic Energy Authority , Culham Campus, Abingdon, Oxon OX14 3DB, United Kingdom of Great Britain and Northern IrelandUnited Kingdom Atomic Energy Authority , Culham Campus, Abingdon, Oxon OX14 3DB, United Kingdom of Great Britain and Northern IrelandUnited Kingdom Atomic Energy Authority , Culham Campus, Abingdon, Oxon OX14 3DB, United Kingdom of Great Britain and Northern IrelandUnited Kingdom Atomic Energy Authority , Culham Campus, Abingdon, Oxon OX14 3DB, United Kingdom of Great Britain and Northern IrelandUnited Kingdom Atomic Energy Authority , Culham Campus, Abingdon, Oxon OX14 3DB, United Kingdom of Great Britain and Northern IrelandUnited Kingdom Atomic Energy Authority , Culham Campus, Abingdon, Oxon OX14 3DB, United Kingdom of Great Britain and Northern IrelandYork Plasma Institute, Department of Physics, University of York , York YO10 5DQ, United Kingdom of Great Britain and Northern IrelandYork Plasma Institute, Department of Physics, University of York , York YO10 5DQ, United Kingdom of Great Britain and Northern IrelandVTT Technical Research Centre of Finland , Espoo FI-02044 VTT, FinlandVTT Technical Research Centre of Finland , Espoo FI-02044 VTT, FinlandUnited Kingdom Atomic Energy Authority , Culham Campus, Abingdon, Oxon OX14 3DB, United Kingdom of Great Britain and Northern IrelandUnited Kingdom Atomic Energy Authority , Culham Campus, Abingdon, Oxon OX14 3DB, United Kingdom of Great Britain and Northern IrelandUnited Kingdom Atomic Energy Authority , Culham Campus, Abingdon, Oxon OX14 3DB, United Kingdom of Great Britain and Northern IrelandUnited Kingdom Atomic Energy Authority , Culham Campus, Abingdon, Oxon OX14 3DB, United Kingdom of Great Britain and Northern IrelandUnited Kingdom Atomic Energy Authority , Culham Campus, Abingdon, Oxon OX14 3DB, United Kingdom of Great Britain and Northern IrelandUnited Kingdom Atomic Energy Authority , Culham Campus, Abingdon, Oxon OX14 3DB, United Kingdom of Great Britain and Northern IrelandUnited Kingdom Atomic Energy Authority , Culham Campus, Abingdon, Oxon OX14 3DB, United Kingdom of Great Britain and Northern IrelandUnited Kingdom Atomic Energy Authority , Culham Campus, Abingdon, Oxon OX14 3DB, United Kingdom of Great Britain and Northern IrelandUnited Kingdom Atomic Energy Authority , Culham Campus, Abingdon, Oxon OX14 3DB, United Kingdom of Great Britain and Northern IrelandUnited Kingdom Atomic Energy Authority , Culham Campus, Abingdon, Oxon OX14 3DB, United Kingdom of Great Britain and Northern IrelandUnited Kingdom Atomic Energy Authority , Culham Campus, Abingdon, Oxon OX14 3DB, United Kingdom of Great Britain and Northern IrelandUnited Kingdom Atomic Energy Authority , Culham Campus, Abingdon, Oxon OX14 3DB, United Kingdom of Great Britain and Northern IrelandUnited Kingdom Atomic Energy Authority , Culham Campus, Abingdon, Oxon OX14 3DB, United Kingdom of Great Britain and Northern IrelandUnited Kingdom Atomic Energy Authority , Culham Campus, Abingdon, Oxon OX14 3DB, United Kingdom of Great Britain and Northern IrelandUnited Kingdom Atomic Energy Authority , Culham Campus, Abingdon, Oxon OX14 3DB, United Kingdom of Great Britain and Northern IrelandUnited Kingdom Atomic Energy Authority , Culham Campus, Abingdon, Oxon OX14 3DB, United Kingdom of Great Britain and Northern IrelandYork Plasma Institute, Department of Physics, University of York , York YO10 5DQ, United Kingdom of Great Britain and Northern IrelandYork Plasma Institute, Department of Physics, University of York , York YO10 5DQ, United Kingdom of Great Britain and Northern IrelandThis paper presents a comprehensive overview of the preliminary divertor design and plasma exhaust scenario for the reactor-class Spherical Tokamak for Energy Production project. Due to the smaller size of the machine, with a major radius less than half that of most DEMO concepts, the current design features a double-null divertor geometry, comprising tightly baffled extended outer legs and shorter inner legs approaching an X-divertor. Leveraging a significant database of SOLPS-ITER simulations, the exhaust operational space is mapped out, offering valuable insights into the plasma exhaust dynamics. An approach involving the validation of simple, yet robust models capable of accurately predicting key exhaust parameters is detailed, thereby streamlining the design process. The simple models are used to simulate the entire plasma scenario from the plasma current ramp-up, through the burning phase, to the plasma current ramp-down. Notably, the findings suggest that pronounced detachment, with peak heat loads below engineering limits and electron temperatures below 5 eV, is achievable with a divertor neutral pressure between 10 Pa and 15 Pa during the burning phase, and pressures below 5 Pa during the ramp-up to maximise the auxiliary current-drive efficiency. Throughout the scenario, an Ar concentration of ${\approx}3$ % in the scrape-off layer (SOL) is required, in combination with a core radiation fraction of 70% driven by intrinsic emission and extrinsic injection of Xe seeded fuelling pellets. However, significant uncertainties remain regarding key parameters such as the SOL heat flux width, Ar screening, and plasma kinetic effects.https://doi.org/10.1088/1741-4326/ad93e7STEPfusiondivertorexhaustreduced models |
| spellingShingle | S.S. Henderson R.T. Osawa S.L. Newton D. Moulton L. Xiang R. Futtersack M. Kryjak C. Ridgers J. Karhunen A. Jarvinen A. Hudoba S. Bakes F. Eriksson H. Meyer M. Lord A. Tarazona A. Cureton A. Barth B. Chuilon T. Hebrard S. Wang Z. Vizvary D. Vaccaro F. Perez Smith J. Farrington J. Harrison B. Dudson B. Lipschultz An overview of the STEP divertor design and the simple models driving the plasma exhaust scenario Nuclear Fusion STEP fusion divertor exhaust reduced models |
| title | An overview of the STEP divertor design and the simple models driving the plasma exhaust scenario |
| title_full | An overview of the STEP divertor design and the simple models driving the plasma exhaust scenario |
| title_fullStr | An overview of the STEP divertor design and the simple models driving the plasma exhaust scenario |
| title_full_unstemmed | An overview of the STEP divertor design and the simple models driving the plasma exhaust scenario |
| title_short | An overview of the STEP divertor design and the simple models driving the plasma exhaust scenario |
| title_sort | overview of the step divertor design and the simple models driving the plasma exhaust scenario |
| topic | STEP fusion divertor exhaust reduced models |
| url | https://doi.org/10.1088/1741-4326/ad93e7 |
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