60 Years of neutral particle analysis: from early tokamaks to ITER M. P. Petrov, V. I. Afanasyev, F. V. Chernyshev, P. R. Goncharov, M. I. Mironov and S. Ya. Petrov EPJ H, 46 1 (2021) 5 Published online: 19 March 2021 DOI: 10.1140/epjh/s13129-021-00009-6