Investigation of LHCD capabilities in I-mode plasma on EAST tokamak

Résumé fourni par la source

Abstract Improved energy confinement mode (I-mode) regime offers promising confinement characteristics with temperature pedestal and low-confinement mode (L-mode) like particle transport. Lower Hybrid Current Drive (LHCD) capability in I-mode is experimentally and numerically investigated. Experimental results show that compared to L-mode plasma, enhanced LHCD efficiency is observed during I-mode plasma, with a broader current profile. Ray-tracing simulations suggest that the observed improvement may be attributed to altered LH wave power deposition caused by the temperature pedestal, which leads to a broader driven current profile. These results underscore the significant impact of edge conditions on LHCD. The edge localized mode-free nature of I-mode provides a stable platform for LHCD, making it attractive for steady-state operation. Note that the potential role of reduced parametric decay instability (PDI) in the edge region cannot be fully excluded due to the lack of direct 2.45 GHz RF spectral measurements and kinetic edge profile in scrape-off layer. Consequently, both interpretations, modified wave propagation and suppressed PDI, remain plausible and further verification by full-wave modeling and dedicated experiments are necessary. Considering that both the PDI and the confinement regimes are closely related to the boundary parameters, the LHCD performance across different confinement regimes under the high-density platform will be further investigated.

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