Numerical assessment of the new V-shape small-angle slot divertor on DIII-D

Maurizio, R.; Du, H.; Gallo, A.; Guo, H. Y.; Leonard, A.; Ma, X.; Sinclair, G.; Stangeby, P.; Thomas, D. M.; Wang, H.; Wilcox, R. S.; Yu, J. H.; Casali, L.; Shafer, M. W.

doi:10.1088/1741-4326/ac27c8

Title: Numerical assessment of the new V-shape small-angle slot divertor on DIII-D

Journal Article · Fri Oct 08 00:00:00 EDT 2021 · Nuclear Fusion

DOI:https://doi.org/10.1088/1741-4326/ac27c8· OSTI ID:1830231

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Oak Ridge Associated Univ., Oak Ridge, TN (United States); General Atomics, San Diego, CA (United States)
Southwestern Inst. of Physics, Chengdu (China)
Oak Ridge Associated Univ., Oak Ridge, TN (United States)
General Atomics, San Diego, CA (United States)
Univ. of Toronto, ON (Canada)
Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
General Atomics, San Diego, CA (United States); Univ. of Tennessee, Knoxville, TN (United States)

The small-angle slot (SAS) divertor of the DIII-D tokamak, and its upcoming upgrade, the V-shape small-angle slot (SAS-V) divertor, are numerically investigated using the SOLPS-ITER code package, including the effect of particle drifts, for a range of plasma density, heating power, strike point position in the slot, and for both magnetic field directions. The simulations show that the electron temperature near the strike point is reduced in SAS-V compared to SAS, for both magnetic field directions, such that SAS-V achieves divertor detachment at a lower value of the outboard mid-plane separatrix electron density. The detachment threshold is lower because the V-shape focuses recycling neutrals on the V-end, densifying and cooling the plasma in the slot. At sufficiently high density, the V-shape also reduces the radial gradient of the temperature profile at the target, which in turns reduces the radial electric field and the E × B drift velocities, further densifying and cooling the plasma in the slot and leading to detachment. The V-shape effect, however, is reduced for higher heating power. With more heating power, the detachment density increases, reducing the ionization mean free path of recycled neutrals, which therefore become less sensitive to target shape changes. This suggests that in a fusion reactor, where the heating power is high, optimization of the divertor target shape needs to be combined with other strategies to lower the detachment density, such as in-slot injection of low-Z impurities.

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Research Organization:: General Atomics, San Diego, CA (United States); Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)

Sponsoring Organization:: USDOE Office of Science (SC), Fusion Energy Sciences (FES)

Grant/Contract Number:: FC02-04ER54698; AC05-00OR22725

OSTI ID:: 1830231

Alternate ID(s):: OSTI ID: 1842602

Report Number(s):: DOE-GA-54698; TRN: US2216445

Journal Information:: Nuclear Fusion, Vol. 61, Issue 11; ISSN 0029-5515

Publisher:: IOP ScienceCopyright Statement

Country of Publication:: United States

Language:: English

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