Considerations on energy confinement time scalings using present tokamak databases and prediction for ITER size experiments
The thermal energy confinement time for International Thermonuclear Experimental Reactor (ITER) size experiments is based on power law scalings obtained using datasets of present tokamak results in specific regimes, the most relevant being the ELMy H-mode regime. A thorough statistical approach has provided a best fit to these data with an estimation of the error bars which forms the basis for the ITER-EDA design parameters. In this report, the range of variation of the main parameters in the database are studied individually and are used to reduce the number of variables in the power law scaling. In this way, it is shown that the four variables are good parameters which provide a simple fit to the data which satisfies the high beta or Kadomstev constraint. This fit is as good as the best log-linear fit, using the 8 variables over the full set of devices used in the databank and it yields the same prediction for the ITER-EDA confinement time. It turns out that this simple best fit is a gyro-Bohm scaling. It is also shown that small changes in the density and P(*) exponents can give a Bohm like scaling, which is less accurate and is pessimistic, but can be used as a lower bound prediction. The use of this simple scaling law is illustrated by a proposal to slightly reduce the size and magnetic field of the ITER-EDA design.
Bibliographic Reference: Report: LRP 616/98 EN (1998) 18pp.
Availability: Available from the Ecole Polytechnique Fédérale de Lausanne, Lausanne (CH)
Record Number: 199811280 / Last updated on: 1998-10-27
Original language: en
Available languages: en