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Journal Articles

The Role of aspect ratio and beta in H-mode confinement scalings

Kaye, S. M.*; Valovic, M.*; Chudnovskiy, A.*; Cordey, J. G.*; McDonald, D.*; Meakins, A.*; Thomsen, K.*; Akers, R.*; Bracco, G.*; Brickley, C.*; et al.

Plasma Physics and Controlled Fusion, 48(5A), p.A429 - A438, 2006/05

 Times Cited Count:13 Percentile:44.28(Physics, Fluids & Plasmas)

The effects of aspect ratio and beta on confinement scaling are studied with the use of the H-mode database extended by the low aspect ratio data from NSTX and MAST. Various statistical methods are applied. Development of scalings using engineering parameters as predictor variables results in the inverse-aspect-ratio scaling with the range from 0.38 to 1.29. The transformation of these scalings to physics variables results in an unfavorouble dependence of the normalized energy confinement time on beta. There is a strong correlation between the inverse aspect ratio and beta, and this makes scalings based on physics variables imprecise.

Journal Articles

The Impact of statistical models on scalings derived from multi-machine H-mode threshold experiments

McDonald, D. C.*; Meakins, A. J.*; Svensson, J.*; Kirk, A.*; Andrew, Y.*; Cordey, J. G.*; Takizuka, Tomonori; ITPA H-mode Threshold Database Working Group*

Plasma Physics and Controlled Fusion, 48(5A), p.A439 - A447, 2006/05

 Times Cited Count:10 Percentile:36.35(Physics, Fluids & Plasmas)

The H-mode power threshold is estimated from the International threshold database by the ordinary least square log-linear regression (OLS), the errors-in-variables log-linear orthogonal regression and the generalized maximum-likekihood (M-L) method. A chi-squared analysis shows that none of the studied models are entirely consistent with the data, indicating that further refinement of the physical and statistical model is required. For ITER-like parameters, a M-L analysis shows a predicted threshold of 38.4 MW, compared with 31.1 MW for the OLS.

Journal Articles

Scaling of the energy confinement time with $$beta$$ and collisionality approaching ITER conditions

Cordey, J. G.*; Thomsen, K.*; Chudnovskiy, A.*; Kardaun, O. J. W. F.*; Takizuka, Tomonori; Snipes, J. A.*; Greenwald, M.*; Sugiyama, L.*; Ryter, F.*; Kus, A.*; et al.

Nuclear Fusion, 45(9), p.1078 - 1084, 2005/09

 Times Cited Count:51 Percentile:84.74(Physics, Fluids & Plasmas)

The condition of the latest version of the ELMy H-mode database has been re-examined. It is shown that there is bias in the ordinary least squares regression for some of the variables. To address these shortcomings three different techniques are employed: (a)principal component regression, (b)an error in variables technique and (c)the selection of a better conditioned dataset with fewer variables. Scalings in terms of the dimensionless physics valiables, as well as the standard set of engineering variables, are derived. The new scalings give a very similar performance for existing scalings for ITER at the standard beta, but a much improvement performance at higher beta.

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