Active Recycling Control Through Lithium Injection in EAST

Journal Article · Thu Feb 01 00:00:00 EST 2018 · IEEE Transactions on Plasma Science

DOI:https://doi.org/10.1109/tps.2017.2789119· OSTI ID:1465373

Canik, J. M.  ^[1]; Sun, Z.  ^[2]; Hu, J. S.  ^[2]; Zuo, G. Z. ^[2]; Xu, W. ^[2]; Huang, M. ^[2]; Wang, L. ^[2]; Xu, J.  ^[2]; Zhang, T. ^[2]; Maingi, R. ^[3]; Lunsford, R. ^[3]; Diallo, A. ^[3]; Mansfield, D. ^[3]; Osborne, T. ^[4]; Tritz, K. ^[5]

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1. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
2. Chinese Academy of Sciences, Hefei (China)
3. Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States)
4. General Atomics, San Diego, CA (United States)
5. Johns Hopkins Univ., Baltimore, MD (United States)

The coating of tokamak walls with thin layers of lithium has been demonstrated to reduce plasma recycling from the plasma-facing surfaces and to improve overall plasma performance. These effects, including reduced divertor D α emission, the elimination of edge-localized modes, and increased energy confinement have been observed in multiple experiments when lithium coatings are applied before plasma discharges. However, this coating technology does not extrapolate to future long-pulse devices, since the lithium coatings will be passivated by the continual plasma flux onto the surface. In order to provide active conditioning capability, a new technology has been developed that is capable of injecting lithium powder into the scrape-off layer plasma during plasma discharges, where it quickly liquefies and turns into an aerosol. The use of this “lithium dropper” is under study at the Experimental Advanced Superconducting Tokamak (EAST), where the potential benefits of real-time wall conditioning via lithium injection are being tested. Here, we present an analysis of the recycling characteristics during EAST experiments testing active lithium injection in order to assess recycling reduction and control. Lithium aerosol was injected from the top of the machine, with one system dropping lithium near the X-point and another into the low-field side divertor leg. The injection of lithium into the SOL reduced divertor recycling, as evidenced by reduced D_α emission with ion flux measured by probes relatively unchanged. This effect is strongest in the active divertor, confirming the lithium is transported to strongly plasma-wetted areas. Furthermore, quantitative analysis of the recycling changes using the SOLPS edge plasma and neutral transport code indicated a ~20% reduction in recycling coefficient with lithium injection.

• Research Organization: Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States)
• Sponsoring Organization: USDOE
• Grant/Contract Number: 2017YFA0402500; 11625524; 11605246; 11775261; AC05-00OR22725; AC02-09CH11466; FC02- 04ER54698; SC0016553
• OSTI ID: 1465373
• Journal Information: IEEE Transactions on Plasma Science, Vol. 46, Issue 5; ISSN 0093-3813
• Publisher: IEEE
• Country of Publication: United States
• Language: English

Related Subjects

70 PLASMA PHYSICS AND FUSION TECHNOLOGY
divertor
Experimental Advanced Superconducting Tokamak (EAST)
lithium wall coatings