Considerations on Stellarator’s Optimization from the Perspective of the Energy Confinement Time Scaling Laws
The Stellarator is a magnetic configuration considered a realistic candidate for a future thermonuclear fusion commercial reactor. The most widely accepted scaling law of the energy confinement time for the Stellarator is the ISS04, which employs a renormalisation factor, <i>f<sub>ren<...
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MDPI AG
2022-03-01
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| Online Access: | https://www.mdpi.com/2076-3417/12/6/2862 |
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| author | Andrea Murari Emmanuele Peluso Luca Spolladore Jesus Vega Michela Gelfusa |
| author_facet | Andrea Murari Emmanuele Peluso Luca Spolladore Jesus Vega Michela Gelfusa |
| author_sort | Andrea Murari |
| collection | DOAJ |
| description | The Stellarator is a magnetic configuration considered a realistic candidate for a future thermonuclear fusion commercial reactor. The most widely accepted scaling law of the energy confinement time for the Stellarator is the ISS04, which employs a renormalisation factor, <i>f<sub>ren</sub></i>, specific to each device and each level of optimisation for individual machines. The <i>f<sub>ren</sub></i> coefficient is believed to account for higher order effects not ascribable to variations in the 0D quantities, the only ones included in the database used to derive ISS04, the International Stellarator Confinement database. This hypothesis is put to the test with symbolic regression, which allows relaxing the assumption that the scaling laws must be in power monomial form. Specific and more general scaling laws for the different magnetic configurations have been identified and perform better than ISS04, even without relying on any renormalisation factor. The proposed new scalings typically present a coefficient of determination R<sup>2</sup> around 0.9, which indicates that they basically exploit all the information included in the database. More importantly, the different optimisation levels are correctly reproduced and can be traced back to variations in the 0D quantities. These results indicate that <i>f<sub>ren</sub></i> is not indispensable to interpret the data because the different levels of optimisation leave clear signatures in the 0D quantities. Moreover, the main mechanism dominating transport, in reasonably optimised configurations, is expected to be turbulence, confirmed by a comparative analysis of the Tokamak in L mode, which shows very similar values of the energy confinement time. Not resorting to any renormalisation factor, the new scaling laws can also be extrapolated to the parameter regions of the most important reactor designs available. |
| first_indexed | 2024-03-09T20:09:58Z |
| format | Article |
| id | doaj.art-ab4afb94798f4564819ad680e3e8ac23 |
| institution | Directory Open Access Journal |
| issn | 2076-3417 |
| language | English |
| last_indexed | 2024-03-09T20:09:58Z |
| publishDate | 2022-03-01 |
| publisher | MDPI AG |
| record_format | Article |
| series | Applied Sciences |
| spelling | doaj.art-ab4afb94798f4564819ad680e3e8ac232023-11-24T00:20:25ZengMDPI AGApplied Sciences2076-34172022-03-01126286210.3390/app12062862Considerations on Stellarator’s Optimization from the Perspective of the Energy Confinement Time Scaling LawsAndrea Murari0Emmanuele Peluso1Luca Spolladore2Jesus Vega3Michela Gelfusa4Consorzio RFX, CNR, ENEA, INFN, Università di Padova, Acciaierie Venete SpA, Corso Stati Uniti 4, 35127 Padova, ItalyDepartment of Industrial Engineering, University of Rome “Tor Vergata”, Via del Politecnico 1, 00133 Roma, ItalyDepartment of Industrial Engineering, University of Rome “Tor Vergata”, Via del Politecnico 1, 00133 Roma, ItalyLaboratorio Nacional de Fusión, CIEMAT. Av. Complutense 40, 28040 Madrid, SpainDepartment of Industrial Engineering, University of Rome “Tor Vergata”, Via del Politecnico 1, 00133 Roma, ItalyThe Stellarator is a magnetic configuration considered a realistic candidate for a future thermonuclear fusion commercial reactor. The most widely accepted scaling law of the energy confinement time for the Stellarator is the ISS04, which employs a renormalisation factor, <i>f<sub>ren</sub></i>, specific to each device and each level of optimisation for individual machines. The <i>f<sub>ren</sub></i> coefficient is believed to account for higher order effects not ascribable to variations in the 0D quantities, the only ones included in the database used to derive ISS04, the International Stellarator Confinement database. This hypothesis is put to the test with symbolic regression, which allows relaxing the assumption that the scaling laws must be in power monomial form. Specific and more general scaling laws for the different magnetic configurations have been identified and perform better than ISS04, even without relying on any renormalisation factor. The proposed new scalings typically present a coefficient of determination R<sup>2</sup> around 0.9, which indicates that they basically exploit all the information included in the database. More importantly, the different optimisation levels are correctly reproduced and can be traced back to variations in the 0D quantities. These results indicate that <i>f<sub>ren</sub></i> is not indispensable to interpret the data because the different levels of optimisation leave clear signatures in the 0D quantities. Moreover, the main mechanism dominating transport, in reasonably optimised configurations, is expected to be turbulence, confirmed by a comparative analysis of the Tokamak in L mode, which shows very similar values of the energy confinement time. Not resorting to any renormalisation factor, the new scaling laws can also be extrapolated to the parameter regions of the most important reactor designs available.https://www.mdpi.com/2076-3417/12/6/2862multimachine databasesscaling lawssymbolic regressiongenetic programmingenergy confinement timestellarator optimisation |
| spellingShingle | Andrea Murari Emmanuele Peluso Luca Spolladore Jesus Vega Michela Gelfusa Considerations on Stellarator’s Optimization from the Perspective of the Energy Confinement Time Scaling Laws Applied Sciences multimachine databases scaling laws symbolic regression genetic programming energy confinement time stellarator optimisation |
| title | Considerations on Stellarator’s Optimization from the Perspective of the Energy Confinement Time Scaling Laws |
| title_full | Considerations on Stellarator’s Optimization from the Perspective of the Energy Confinement Time Scaling Laws |
| title_fullStr | Considerations on Stellarator’s Optimization from the Perspective of the Energy Confinement Time Scaling Laws |
| title_full_unstemmed | Considerations on Stellarator’s Optimization from the Perspective of the Energy Confinement Time Scaling Laws |
| title_short | Considerations on Stellarator’s Optimization from the Perspective of the Energy Confinement Time Scaling Laws |
| title_sort | considerations on stellarator s optimization from the perspective of the energy confinement time scaling laws |
| topic | multimachine databases scaling laws symbolic regression genetic programming energy confinement time stellarator optimisation |
| url | https://www.mdpi.com/2076-3417/12/6/2862 |
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