Error field analysis of steady state tokamak reactor with ferromagnetic (F82H) blanket

Error fields generated by a ferromagnetic steel (reduced activation ferritic steel: F82H) blanket were estimated in a conceptual design of the steady state tokamak reactor. The amplitude of radial error field with the poloidal mode number=2 and the toroidal mode number=1 (ΔB_r21), which results in locked mode disruptions, was about 0.4 G at the plasma surface, while the maximum radial error field was about 600 G at the port edges. The relative error field (ΔB_r21/B_T≈4.5×10^-6 where B_T is the toroidal field of 9T) was comparable with the predicted critical relative error field for locked modes