A simple, accurate model for detachment access
In next-step fusion tokamaks such as SPARC and ITER, achieving high levels of scrape-off-layer power dissipation will be essential to protect the divertor while maintaining good core plasma performance. The Lengyel model for power dissipation is easy to interpret and fast enough to incorporate into...
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| Format: | Article |
| Language: | English |
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IOP Publishing
2025-01-01
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| Series: | Nuclear Fusion |
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| Online Access: | https://doi.org/10.1088/1741-4326/ade4d9 |
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| author | Thomas Body Arne Kallenbach Thomas Eich |
| author_facet | Thomas Body Arne Kallenbach Thomas Eich |
| author_sort | Thomas Body |
| collection | DOAJ |
| description | In next-step fusion tokamaks such as SPARC and ITER, achieving high levels of scrape-off-layer power dissipation will be essential to protect the divertor while maintaining good core plasma performance. The Lengyel model for power dissipation is easy to interpret and fast enough to incorporate into plasma control and scoping tools, but it systematically overestimates the impurity concentration required to reach detachment by a factor of ${\sim}5$ relative to experiments and higher-fidelity simulations. In this work, we extended the Lengyel model to match the semi-empirical Kallenbach scaling, which successfully describes detachment access on several operating tokamaks. We found that we can reproduce the experimental scaling by accounting for cross-field transport in the divertor, power and momentum loss due to neutral ionization close to the divertor target and turbulent broadening of the upstream heat flux channel. These corrections cause the impurity concentration required for detachment to decrease faster than $n_{e,u}^2$ , reproducing the $c_z\propto 1/n_{e,u}^{2.7-3.2}$ scalings found in experiment. The model also quantitatively reproduces the impurity concentration needed to reach detachment in experiment, demonstrating that the extended Lengyel model can be used as a simple, accurate model for detachment access. |
| format | Article |
| id | doaj-art-c8f7071a31bc4c72a6262a1c81f5a7be |
| institution | Matheson Library |
| issn | 0029-5515 |
| language | English |
| publishDate | 2025-01-01 |
| publisher | IOP Publishing |
| record_format | Article |
| series | Nuclear Fusion |
| spelling | doaj-art-c8f7071a31bc4c72a6262a1c81f5a7be2025-06-30T07:56:44ZengIOP PublishingNuclear Fusion0029-55152025-01-0165808600210.1088/1741-4326/ade4d9A simple, accurate model for detachment accessThomas Body0https://orcid.org/0000-0003-1904-6300Arne Kallenbach1https://orcid.org/0000-0003-0538-2493Thomas Eich2https://orcid.org/0000-0003-3065-8420Commonwealth Fusion Systems , 117 Hospital Rd, Devens, MA 01434, United States of AmericaMax Planck Institute for Plasma Physics , Boltzmannstr. 2, Garching 85748, GermanyCommonwealth Fusion Systems , 117 Hospital Rd, Devens, MA 01434, United States of AmericaIn next-step fusion tokamaks such as SPARC and ITER, achieving high levels of scrape-off-layer power dissipation will be essential to protect the divertor while maintaining good core plasma performance. The Lengyel model for power dissipation is easy to interpret and fast enough to incorporate into plasma control and scoping tools, but it systematically overestimates the impurity concentration required to reach detachment by a factor of ${\sim}5$ relative to experiments and higher-fidelity simulations. In this work, we extended the Lengyel model to match the semi-empirical Kallenbach scaling, which successfully describes detachment access on several operating tokamaks. We found that we can reproduce the experimental scaling by accounting for cross-field transport in the divertor, power and momentum loss due to neutral ionization close to the divertor target and turbulent broadening of the upstream heat flux channel. These corrections cause the impurity concentration required for detachment to decrease faster than $n_{e,u}^2$ , reproducing the $c_z\propto 1/n_{e,u}^{2.7-3.2}$ scalings found in experiment. The model also quantitatively reproduces the impurity concentration needed to reach detachment in experiment, demonstrating that the extended Lengyel model can be used as a simple, accurate model for detachment access.https://doi.org/10.1088/1741-4326/ade4d9divertor detachmentimpurity seedingtokamakdetachment onsetreduced model |
| spellingShingle | Thomas Body Arne Kallenbach Thomas Eich A simple, accurate model for detachment access Nuclear Fusion divertor detachment impurity seeding tokamak detachment onset reduced model |
| title | A simple, accurate model for detachment access |
| title_full | A simple, accurate model for detachment access |
| title_fullStr | A simple, accurate model for detachment access |
| title_full_unstemmed | A simple, accurate model for detachment access |
| title_short | A simple, accurate model for detachment access |
| title_sort | simple accurate model for detachment access |
| topic | divertor detachment impurity seeding tokamak detachment onset reduced model |
| url | https://doi.org/10.1088/1741-4326/ade4d9 |
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