# Performance assessment of long-legged tightly-baffled divertor geometries in the ARC reactor concept

## Abstract

Abstract Extremely intense power exhaust channels are projected for tokamak-based fusion power reactors; a means to handle them remains to be demonstrated. Advanced divertor configurations have been proposed as potential solutions. Recent modelling of tightly baffled, long-legged divertor geometries for the divertor test tokamak concept, ADX, has shown that these concepts may access passively stable, fully detached regimes over a broad range of parameters. The question remains as to how such divertors may perform in a reactor setting. To explore this, numerical simulations are performed with UEDGE for the long-legged divertor geometry proposed for the ARC pilot plant conceptual design—a device with projected heat flux power width ( ) of 0.4 mm and power exhaust of 93 MW—first for a simplified Super-X divertor configuration (SXD) and then for the actual X-point target divertor (XPTD) being proposed. It is found that the SXD, combined with 0.5% fixed-fraction neon impurity concentration, can produce passively stable, detached divertor regimes for power exhausts in the range of 80–108 MW—fully accommodating ARC’s power exhaust. The XPTD configuration is found to reduce the strike-point temperature by a factor of ∼10 compared to the SXD for small separations (∼1.4 ) between main and divertor X-point magnetic flux surfaces. Evenmore »

- Authors:

- Publication Date:

- Sponsoring Org.:
- USDOE

- OSTI Identifier:
- 1564344

- Resource Type:
- Published Article

- Journal Name:
- Nuclear Fusion

- Additional Journal Information:
- Journal Name: Nuclear Fusion Journal Volume: 59 Journal Issue: 10; Journal ID: ISSN 0029-5515

- Publisher:
- IOP Publishing

- Country of Publication:
- IAEA

- Language:
- English

## Citation Formats

```
Wigram, M. R. K., LaBombard, B., Umansky, M. V., Kuang, A. Q., Golfinopoulos, T., Terry, J. L., Brunner, D., Rensink, M. E., Ridgers, C. P., and Whyte, D. G. Performance assessment of long-legged tightly-baffled divertor geometries in the ARC reactor concept. IAEA: N. p., 2019.
Web. doi:10.1088/1741-4326/ab394f.
```

```
Wigram, M. R. K., LaBombard, B., Umansky, M. V., Kuang, A. Q., Golfinopoulos, T., Terry, J. L., Brunner, D., Rensink, M. E., Ridgers, C. P., & Whyte, D. G. Performance assessment of long-legged tightly-baffled divertor geometries in the ARC reactor concept. IAEA. https://doi.org/10.1088/1741-4326/ab394f
```

```
Wigram, M. R. K., LaBombard, B., Umansky, M. V., Kuang, A. Q., Golfinopoulos, T., Terry, J. L., Brunner, D., Rensink, M. E., Ridgers, C. P., and Whyte, D. G. Thu .
"Performance assessment of long-legged tightly-baffled divertor geometries in the ARC reactor concept". IAEA. https://doi.org/10.1088/1741-4326/ab394f.
```

```
@article{osti_1564344,
```

title = {Performance assessment of long-legged tightly-baffled divertor geometries in the ARC reactor concept},

author = {Wigram, M. R. K. and LaBombard, B. and Umansky, M. V. and Kuang, A. Q. and Golfinopoulos, T. and Terry, J. L. and Brunner, D. and Rensink, M. E. and Ridgers, C. P. and Whyte, D. G.},

abstractNote = {Abstract Extremely intense power exhaust channels are projected for tokamak-based fusion power reactors; a means to handle them remains to be demonstrated. Advanced divertor configurations have been proposed as potential solutions. Recent modelling of tightly baffled, long-legged divertor geometries for the divertor test tokamak concept, ADX, has shown that these concepts may access passively stable, fully detached regimes over a broad range of parameters. The question remains as to how such divertors may perform in a reactor setting. To explore this, numerical simulations are performed with UEDGE for the long-legged divertor geometry proposed for the ARC pilot plant conceptual design—a device with projected heat flux power width ( ) of 0.4 mm and power exhaust of 93 MW—first for a simplified Super-X divertor configuration (SXD) and then for the actual X-point target divertor (XPTD) being proposed. It is found that the SXD, combined with 0.5% fixed-fraction neon impurity concentration, can produce passively stable, detached divertor regimes for power exhausts in the range of 80–108 MW—fully accommodating ARC’s power exhaust. The XPTD configuration is found to reduce the strike-point temperature by a factor of ∼10 compared to the SXD for small separations (∼1.4 ) between main and divertor X-point magnetic flux surfaces. Even greater potential reductions are identified for reducing separations to ∼1 or less. The power handling response is found to be insensitive to the level of cross-field convective or diffusive transport assumed in the divertor leg. By raising the separatrix density by a factor of 1.5, stable fully detached divertor solutions are obtained that fully accommodate the ARC exhaust power without impurity seeding. To our knowledge, this is the first time an impurity-free divertor power handling scenario has been obtained in edge modelling for a tokamak fusion power reactor with of 0.4 mm.},

doi = {10.1088/1741-4326/ab394f},

journal = {Nuclear Fusion},

number = 10,

volume = 59,

place = {IAEA},

year = {2019},

month = {9}

}

https://doi.org/10.1088/1741-4326/ab394f

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