A major upgrade is underway for Pegasus Phase III (Pegasus-III). The new facility will provide a dedicated U.S. platform that will compare, contrast, and combine different concepts for solenoid-free startup. This approach will allow for a more integrated study of the leading startup and possibly sustainment techniques, including local helicity injection (LHI), transient and sustained coaxial helicity injection (CHI), radiofrequency heating and current drive, external magnetic field induction, and neutral beam injection (future). The goal of the facility is to develop a validated concept for 1 MA plasma startup on the U.S. flagship facility NSTX-U and beyond. Construction of Pegasus-III is underway, and the facility will be operational in 2020.
Features and Research
Pegasus-III will feature many facility enhancements that will allow for the study of several areas of exciting physics and engineering research. Included in the new facility features are a solenoid-free central column, a stronger, high toroidal field assembly, new power systems, active divertor coils, next-generation LHI, coaxial helicity injection (CHI), RF startup and assist, and expanded diagnostics.
Projecting LHI to larger facilities requires tests at increasing toroidal field. Pegasus-III will enable investigation of LHI at increased field levels, allowing for the testing of key physics issues such as as core confinement, reconnection and current drive, stochastic edge transport, and current stream stability. Along with these physics developments is the advancement of LHI technology, including the installation and testing of a non-circular injector concept. Increased toroidal field also enables comparative studies of CHI. Included in this are both improved technology development and more physics studies. This will involve improved CHI technology development, including a new electrode configuration, as well as exploration of CHI physics at higher toroidal field. **Mention collaborators?** Pegasus-III will also explore RF heating and current drive capabilities. The initial focus will be on EBW synergies with helicity injection, namely improved startup via electron heating and EBW current drive as a current sustainment mechanism post-helicity injection startup. **Mention collaborators?**