Radiation-front position control with scenario adjustments during the first tungsten divertor operation on KSTAR

Byun, CheolSik [Princeton Univ., NJ (United States)] (ORCID:0009000708691116); Oh, S. [Korea Institute of Fusion Energy (KFE), Daejeon (Korea, Republic of)]; Kim, SangKyeun [Princeton Plasma Physics Laboratory (PPPL), Princeton, NJ (United States)] (ORCID:0000000207018962); Kim, Boseong [Korea Institute of Fusion Energy (KFE), Daejeon (Korea, Republic of); Seoul National Univ. (Korea, Republic of)]; Han, Yoon Seong [Korea Advanced Institute Science and Technology (KAIST), Daejeon (Korea, Republic of)]; Hahn, Sang-hee [Korea Institute of Fusion Energy (KFE), Daejeon (Korea, Republic of)] (ORCID:0000000181159248); Lee, H. H. [Korea Institute of Fusion Energy (KFE), Daejeon (Korea, Republic of)]; Jalalvand, Azarakhsh [Princeton Univ., NJ (United States)]; Lee, Youngho [Korea Institute of Fusion Energy (KFE), Daejeon (Korea, Republic of)] (ORCID:0000000252854599); Hwang, Junghoo [Korea Institute of Fusion Energy (KFE), Daejeon (Korea, Republic of); Korea Advanced Institute Science and Technology (KAIST), Daejeon (Korea, Republic of)]; Shousha, Ricardo [Princeton Plasma Physics Laboratory (PPPL), Princeton, NJ (United States)] (ORCID:0000000314988980); Park, Jae-Sun [Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States)] (ORCID:0000000308717527); Kolemen, Egemen [Princeton Univ., NJ (United States); Princeton Plasma Physics Laboratory (PPPL), Princeton, NJ (United States)] (ORCID:0000000342123247)

doi:10.1088/1741-4326/ae4d24

DOE OSTI · 3025219

Radiation-front position control with scenario adjustments during the first tungsten divertor operation on KSTAR

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Abstract

This study reports the first experimental demonstration of a radiation front-based detachment control system during the initial tungsten divertor campaign in KSTAR. The system employs real-time infrared video bolometry with tomographic reconstruction to track the inboard radiation-front position, which served as a feedback variable for impurity seeding. In a baseline scenario without pre-D 2 fueling, tungsten accumulation triggered core radiation surges and repetitive H–L back transitions. In contrast, with pre-D 2 fueling, detachment was stabilized by maintaining higher edge-localized mode frequency, suppressing core tungsten buildup, and reducing sputtering, thereby enabling sustained feedback control. The suitability of the inboard front position as a detachment control metric was confirmed by its correlation with the degree of detachment: with D 2 fueling the relation exhibited a broad hysteresis loop characteristic of momentum-loss-dominated detachment, whereas with N 2 fueling, it became narrow and nearly vertical, consistent with radiation-loss-dominated pinning. These results provide a proof-of-principle for radiation-front-based detachment control, demonstrating its viability as a control approach. At the same time, these results clarify that the detachment outcomes were further conditioned by impurity transport characteristics of tungsten divertor operation in KSTAR, providing guidance for future scenario optimization and controller development in tungsten devices.

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Byun, CheolSik [Princeton Univ., NJ (United States)] (ORCID:0009000708691116), Oh, S. [Korea Institute of Fusion Energy (KFE), Daejeon (Korea, Republic of)], Kim, SangKyeun [Princeton Plasma Physics Laboratory (PPPL), Princeton, NJ (United States)] (ORCID:0000000207018962), Kim, Boseong [Korea Institute of Fusion Energy (KFE), Daejeon (Korea, Republic of); Seoul National Univ. (Korea, Republic of)], Han, Yoon Seong [Korea Advanced Institute Science and Technology (KAIST), Daejeon (Korea, Republic of)], Hahn, Sang-hee [Korea Institute of Fusion Energy (KFE), Daejeon (Korea, Republic of)] (ORCID:0000000181159248), Lee, H. H. [Korea Institute of Fusion Energy (KFE), Daejeon (Korea, Republic of)], Jalalvand, Azarakhsh [Princeton Univ., NJ (United States)], Lee, Youngho [Korea Institute of Fusion Energy (KFE), Daejeon (Korea, Republic of)] (ORCID:0000000252854599), Hwang, Junghoo [Korea Institute of Fusion Energy (KFE), Daejeon (Korea, Republic of); Korea Advanced Institute Science and Technology (KAIST), Daejeon (Korea, Republic of)], Shousha, Ricardo [Princeton Plasma Physics Laboratory (PPPL), Princeton, NJ (United States)] (ORCID:0000000314988980), Park, Jae-Sun [Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States)] (ORCID:0000000308717527), Kolemen, Egemen [Princeton Univ., NJ (United States); Princeton Plasma Physics Laboratory (PPPL), Princeton, NJ (United States)] (ORCID:0000000342123247). 2026-03-18. Radiation-front position control with scenario adjustments during the first tungsten divertor operation on KSTAR. https://doi.org/10.1088/1741-4326%2Fae4d24

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