Scale-up of spherical tokamak solenoid-free startup by coaxial helicity injection

摘要

Current multiplication and flux amplification are two critical measures in assessing the usefulness of magnetic helicity injection for forming the plasma confining magnetic field in laboratory spheromak and spherical tokamak (ST) experiments. While the two concepts are closely related for spheromaks, they are independent for a Taylor-relaxed ST plasma, and negatively correlated for a more realistic, partially relaxed ST plasma. An important application of this understanding leads to the so-called relaxed transient coaxial helicity injection scheme for solenoid-free ST startup, which can deliver reactor-grade high current multiplication and flux amplification. (C) 2007 American Institute of Physics.