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Description
This paper presents the design and construction of a Divertor Fueling System (DFS) developed for the advanced KSTAR operation under diverted discharge configurations aimed at enabling mainly high-density plasma operation and detachment control. The fueling system essential for plasma initiation, density regulation, radifo-frequency (RF) heating coupling, vacuum-wall impurity flushing, radiative-cooling experiments, and mitigation of plasma disruption has been designed with each component tailored to its functional role.
The DFS is built on the gas-injection infrastructure originally installed for the main gas injection system. Its mechanical assembly comprises gas supply, branching, storage, injection, and port-side distribution subsystems, while the control architecture includes data logging and valve actuation. For rapid fueling, ten high-speed piezoelectric injection valves have been employed. The valves are actuated via a digital valve controller that receives real-time command signals from the Plasma Control System (PCS), allowing precise and real-time control. Each piezo valve uses a disk-bender piezo element driven by bias voltage in range of 0–250 V, enabling proportional gas influx according to the applied voltage. The valve design achieves opening/closing response times below 2 ms and delivers a maximum flow exceeding 500 Torr·ℓ/s.
Additionally, the system segregates gas species and injection zones (ports), by a number of manifolds enabling multiple ports, multi-zone gas injection into the divertor region, thereby ensuring not only stable and precise gas delivery but more detailed study of the detachement control. Annual measurements of injected gas amounts per species are recorded and provided, enabling versatile use across various plasma experiments. The implemented design and construction is expected to meet the demanding requirements for high-density plasma fueling and detachment control in KSTAR divertor operations.