X-point radiator and power exhaust control in configurations with multiple X-points in TCV
Novel power exhaust solutions are being developed to address the challenge of integrating a high performance fusion core plasma with a well-protected divertor, if the single null configuration does not scale to a reactor device. This work aims to elucidate the physics mechanisms responsible for the reduction in peak target heat flux in configurations with multiple X-points. Experimental studies on tokamak à configuration variable in the Snowflake Minus configuration are extended to a novel configuration with three nearby divertor X-points, termed a Jellyfish, allowing us to enhance the expected effects of an additional divertor X-point. These studies are complemented by simplified 1D scrape-off layer (SOL) modeling with the SPLEND1D code and by interpretative modeling with the edge transport code EMC3-EIRENE applied to the Snowflake Minus, to further elucidate some of the key underlying processes. We find that configurations with multiple nearby X-points, and increased near-SOL connection length, exhibit reductions in peak target heat flux and an earlier detachment onset compared to a reference single null configuration, consistent with expectations from SPLEND1D. A strong correlation is experimentally observed between the radially localized radiated power and connection length. While this does not necessarily map to higher total divertor radiative losses for configurations with multiple X-points, it can, at least, provide some control over the radial position of the spatial radiation distribution. Experiments are shown to exhibit radial striations in the emissivity of multiple spectral lines in the inter-null region in these configurations. Although comparisons with EMC3-EIRENE simulations support enhanced cross field transport in the inter-null region, additional transport physics is required in the model to obtain a quantitative match with experiment. No significant differences in divertor-core compatibility are attributed to the presence of additional divertor X-points. However, impurity source optimization is required in such geometries to ensure a low core impurity content is maintained.
2-s2.0-85199104845
École Polytechnique Fédérale de Lausanne
École Polytechnique Fédérale de Lausanne
École Polytechnique Fédérale de Lausanne
DeepMind Technologies Limited
École Polytechnique Fédérale de Lausanne
Max Planck Institute for Plasma Physics
École Polytechnique Fédérale de Lausanne
École Polytechnique Fédérale de Lausanne
École Polytechnique Fédérale de Lausanne
DeepMind Technologies Limited
2024-07-01
31
7
072504
REVIEWED
EPFL
| Funder | Funding(s) | Grant Number | Grant URL |
Swiss National Science Foundation | |||
European Commission or SERI | |||
SERI | |||
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