2025 – Shape and scenario development for materials thrust

Shape and scenario development for materials thrust

2025 Research Campaign, Plasma Control

Purpose of Experiment

This Controls Development session will enable the success of FPP Candidate Wall Materials Thrust experiments. 3 1/2 experiment days are allocated under the thrust in FY25, all of which will use DiMES and LSN discharges. In order to maintain compatibility and comparability across experiments, we need to develop a set of reference shots that the majority of proposals/session leaders can use. We will build off of the successful Controls Development efforts in 2024 to better refine the thrust reference discharges, adjusting the programmed strike point location, NBI power, and flux expansion at DiMES. Precise strike-point control at DiMES will be a main focus of this experiment. We will implement a “rastering” control algorithm that sweeps the SP locally across DIMES, using reference shot 200083 from last year (H-mode) as a starting point for scenario optimization.

Experimental Approach

Therefore, this controls development session will be conducted in two stages: 1) optimize the standard H-mode reference shot, and 2) adjust ELM magnitude for an enhanced reference shot. Since the standard H-mode reference is higher priority and will require more time, that reference will be explored first. Under H-mode ELM-ing conditions, specialized DiMES configurations will allow samples to achieve FPP-relevant heat loads of 10-15 MW/m^2 on angled sample surfaces. The H-mode solution to be tested here is to locally sweep or raster the plasma strike point (SP) across the 5 cm DiMES surface, varying scan distance, injected power, and upper triangularity to control local heat fluxes and ELM characteristics.

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