PPPL Collaborations on International Spherical Tokamaks

The Princeton Plasma Physics Laboratory (PPPL) is home to the National Spherical Torus Experiment Upgrade (NSTX-U), which is currently in a recovery project and will return to operations in 2026. In the meantime, PPPL researchers are engaged in collaborations with various spherical tokamaks including MAST-U and ST40 in the UK and SMART in Spain. For MAST-U a database of pedestal characteristics was created and it was determined that higher elongation, lower triangularity plasmas generally had higher, narrower pedestals, while a machine learning framework found that a simple power-law relation between pedestal width and height had low accuracy, but including total plasma pressure, elongation, and Greenwald fraction significantly improved accuracy. For SMART, PPPL researchers designed and implemented the Thomson scattering diagnostic, helped design the spectrometers and diodes for impurity radiation measurements as well as produced estimated calculations of radiated power, analyzed the orbits of energetic particles from a planned neutral beam injector installation, and performed a scoping study of possible future RF heating upgrades.



*This work is supported by the US DOE Contract No. DE-AC02-09CH11466.