FY2025

CONDITIONAL FY25 Research Milestones

R(25-1):  Transport studies and operational support on ST40

Description: ST40 is a small, high toroidal field spherical tokamak with 2 MW of neutral beam heating owned and operated by Tokamak Energy, UK. Collaborative work through a PPPL/ORNL CRADA with Tokamak Energy has helped ST40 researchers achieve their main business milestone of producing plasmas with 100M degree ion temperatures at toroidal fields of over 2 T, more than a factor of two greater than toroidal fields in present STs. The ST40 physics program planned for their first physics campaign in FY24 will focus on developing robust diverted H-mode plasmas and characterizing their performance as a function of plasma current and toroidal field. PPPL personnel will help lead these experiments and analyze the results. The TRANSP code will be used to determine the transport characteristics of these plasmas, in particular, to assess the dependence of the transport and confinement on collisionality to determine whether this dependence remains strong at high toroidal field. The TRANSP calculations will be used as a basis for subsequent gyrokinetic studies, to understand the nature of the underlying transport, and to produce energetic particle distribution functions for subsequently assessing energetic particle confinement and energetic particle-driven modes. Operational support will include implementing a novel algorithm to calculate plasma current from Rogowski coil, as well as developing scenarios for RF experiments to begin in CY26. 

R(25-2): Scenario development and diagnostic support for SMART

Description: SMART is a spherical tokamak at the University of Seville in Spain with flexible shaping ability with the goal of exploring the potential advantages of combining low aspect ratio and negative triangularity after plasma operations commence. Collaborative work between PPPL and SMART has already explored the optimization of future neutral beam injection in SMART as well as contributed to stability assessment of future SMART plasmas. PPPL personnel have designed a Thomson Scattering diagnostic system for SMART and will now provide and implement that diagnostic and assist in obtaining the first measurements of electron temperature and density in phase 1 of operations. PPPL will also assist with the magnetic diagnostic measurements, including AC compensation for the plasma current measurement. Additionally, the TRANSP code will be used to design scenarios for phases 2 and 3 of SMART, and give performance predictions by applying reduced turbulence models.