A. Fukuyama

K. Itoh

M. Azumi

M. Yagi

S.-I. Itoh

National Institute for Fusion Science (NIFS-Repository)

§30. Isotope Effect on Confinement in DT Plas-mas Fukuyama, A. (Okayama Univ.) ltoh, K. ltoh, S.-1. (Kyushu Univ.) Yagi, M., Azumi, M. (JAERI) We have recently developed a theory of the anomalous transport in tokamak:s based on the theory of self-sustained turbulence [1]. The explicit formula of the thermal conductivity was obtained. The comparison with L-mode has been done, and a substantial agreement was found not only in the global confinement nature but also on the bahaviours of the local thermal conductivity. The model was extended to investigate the improved confinement mode [2]. It was predicted that the plasma pressure and toroidal current show the self-organization of the plasma structure, leading to the improvement of the confinement for (3p > 1 [2]. The theoretical formula was approximately given as _/ A0.76 't'r;'t'EL ::- Pp for the high f3p plasmas, where 't'E is the energy confinement time of the thermal particles and 'tEL is the confinement time in the L-mode. The dependence of was obtained theoretically. Note that this enhancement is realized without the gain associated with the edge pedestal profile as in the H-mode. This improvement is generated by the reduced geodesic curvature. This change is . due to the reduced magnetic shear by the large Bootstrap current. (See [2] for the detailed argument for the mechanism of the improvement.) Based on this theoretical result, we employ a connection formula Using this formula, the isotope dependence is calculated. It is emphasized that the increment of 'tEL by the isotope effect is magnified by the improved confinement due to the high f3p effect. We estimate the energy confinement time of DT plasma by substituting A=2.5 and that forD plasma by taking A=2. In performing this comparison, other parameters 142 (including the density profile and the heating profile) are assumed to be common to DT and DD plasmas. Figure 1 compares 'tE{DT) and 't'E{DD) as a function of the pP value of the D plasma. The heating power is varied to change J3p. Asymptotic formula is obtained analyticaJ.ly. It is found that and We see that the energy confinement time of the DT plasma could be 20% better than the corresponding DO plasma, when the experiment utilizes the high (3p condition. TE (DT) rdDD) 1.2 : . 1 -I I 1 .0 '-------'---------'---___j 0 2 3 ,Bp(DD) Fig.l Ratio of the energy confinement times for DT and DO plasmas as a function of (3p of DD plasma. References 1) K. ltoh, et al.: Plasma Phys. Contr. Fusion 35 (1993) 543, 36 (1994) 279. 2) A. Fukuyama et al.: Research Report FURKU 93-05, Kyushu Univ., 1993 4 

Isotope Effect on Confinement in DT Plasmas

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