A dimensional extrapolation technique for ITER

A novel methodology for extrapolation of the performance of ITER class mach ines is introduced. This procedure utilizes the ITER ELMy H mode database b y means of a similarity approach where every discharge is extrapolated to a machine satisfying the ITER performance requirements through the use of th e tokamak system code developed during the course of the ITER design evolut ion. This approach attempts, amongst other things, to overcome the difficul ty associated with the simultaneous choice of non-dimensional parameters wh ich, in particular when close to their respective limits, may have some sig nificant mutual interactions affecting energy confinement time. The methodo logy is also applied to the ITER Physics Basis scalings to develop a non-st atistical approach where fusion power is extrapolated at constant beta and confinement is assumed to follow a gyroBohm form. In both cases, out of mor e than a thousand discharges in the ELMy H mode database, less than half tu rn out to extrapolate to a Q = 10 machine whose major radius is smaller tha n 8 m. However, a significant number of discharges do extrapolate to a Q = 10 machine with R < 6.2 m. This strengthens confidence in the present choic e of ITER parameters. In addition, from this analysis, it has been possible to identify a set of high performance 'ITER relevant' discharges from a nu mber of machines, which could be used as starting points for investigation of further improvements in confinement.