Research and development plans and current activities for the next step tokamak at JAERI are outlined. JAERI's activities are in line with a basic plan for long-term nuclear fusion research and development laid out by the Nuclear Fusion Council (NFC) of the Atomic Energy Commission in October 1986. A brief review is given of the basic concept of the next step nuclear fusion research and development program of NFC. Design studies to establish a concept of the next step tokamak on the basis of major specifications set up by NFC are described together with current R & D activities and future plans of fusion reactor technologies at JAERI.
For a plasma which contains many kinds of molecular species and their fragments, diagnostics of particle identification are particularly important. Spectroscopic methods for these purposes are described. Present status of diagnostics for processing plasmas is shown by papers presented on the last International Symposium on Plasma Chemistry.
A new numerical method named HIDM (higher order implicit difference method) is developed. The HIDM can solve general forms of differential equation Li (ψ1, ψ2, ……, ψN, ψ'1, ψ'2, ……, ψ'N, t) = 0 (i=1, 2, ……, N), including stiff ordinary differential equations. Good performance of the HIDM is shown by several numerical examples.