R24-1: Development of optimized neutral beam and performance scenarios in SMART
Description: SMART is a small-scale spherical tokamak being built by the University of Seville, Spain whose research objectives are to study the performance of both positive and negative triangularity plasmas. This Research Milestone extends the FY23 deliverables by targeting the development of optimized neutral beam configurations and plasma performance in Phases 2 and 3 of SMART operation, when 0.4 MW of neutral beam heating is expected to be available. Specifically, the optimization studies will target 1) development of NB configurations that minimize fast ion loss and maximize plasma heating while providing flexibility to vary the fast ion distribution and study the impact on plasma instabilities driven or affected by NB ions, and 2) maximize plasma performance (confinement) and enable transport studies of both the plasma and the fast ions. This study may include an assessment of the validity and limitations of guiding center vs full orbit approaches to determining NB deposition and physics in compact ST configurations. This assessment follows from similar ones on MAST(-U) and NSTX(-U), and may have implications for compact ST FPP designs.
R24-2: Advancing Spherical Tokamak Physics on the MAST-U Device
Description: NSTX-U researcher’s participation in MAST-U research aims to advance the understanding of spherical tokamak physics in key areas for the benefit of the worldwide ST program, including informing NSTX-U research when it resumes and increasing the confidence of projections in ongoing ST fusion pilot plant design programs. With a goal of predicting ST pedestal widths and heights with newly developed tools, it will be determined whether resistive peeling-ballooning modes are unstable in MAST and MAST-U, the width-height scaling in MAST-U will be modeled using gyrokinetic stability, and the results will be compared with NSTX(/-U). Edge and scrape-off layer transport will also be assessed by investigating whether micro-tearing modes can be destabilized and identified, and by characterizing filamentary transport. Low frequency plasma response to 3D magnetic perturbations and resonant field amplification are being studied in MAST-U, but these could also potentially benefit from improvements of the magnetic diagnostic system, which will be proposed.