Kobayashi, S., Nagasaki, K., Hada, K., Stange, T., Okada, H., Minami, T., et al. (2021). Role of pre-ionization in NBI plasma start-up of Heliotron J using non-resonant microwave heating. Nuclear Fusion, 61: 116009. doi:10.1088/1741-4326/ac2105.