H モード周辺プラズマの無次元量解析

1. Japan Atomic Energy Agency Hモード周辺プラズマの無次元量解析 浦野　創 原子力機構 那珂核融合研究所 Japan Atomic Energy Agency, Naka Fusion Institute

2. Introduction H-mode is considered as the standard operation mode in ITER. • Steady state with the existence of ELM accompanied by pulsating expulsion of heat and particle. • Favorable confinement due to edge transport barrier width Pedestal characteristics can strongly be linked to • Boundary condition determining the core energy confinement • Characterization of ELM losses Japan Atomic Energy Agency, Naka Fusion Institute

3. Dimensionless analysis on spatial width of H-mode pedestal Optimizing pedestal widthDped and height is a crucial issue to control the overall H-mode confinement. Dimensionless analysis is urgent issue for extrapolation to ITER. Dped expressed by non-dimensional parameters are not consistent among several devices. This is because a strong co-linearity between r* and b is hard to separate out at the plasma edge. r*xbz F(n*, q, e, k, d, …) = Dped* Examine the scaling of pedestal width by conducting the non-dimensional transport experiment introducing hydrogen discharges. Japan Atomic Energy Agency, Naka Fusion Institute

4. Co-linearity between r* and b at the plasma edge in the H-modes Dependence of pped on Ip yields b and r* as a function of Ip at n* = const. µ µ n n T T I Ip1.0-1.5 This co-linearity is hard to separate in the H-mode plasmas only with a single species. Japan Atomic Energy Agency, Naka Fusion Institute

5. Examine dependence on r* introducing hydrogen plasmas (H. Urano, et al., NF 48 (2008) 045008) Examine the dependence of Dped on b or r* while keeping total bpol fixed in hydrogen and deuterium H-modes. (1) If DPED r*, spatial profiles would deviate by m0.5. (2) If DPED b, spatial profiles would be similar. CONDITION: IP~1MA, BT~2, DELTA~0.3 Similar profiles are obtained in H/D plasmas. This result implies r* dependence is weak. Japan Atomic Energy Agency, Naka Fusion Institute Japan Atomic Energy Agency, Naka Fusion Institute JT-60U Tokamak: p. 5

6. Experiments on r* dependence of Dped Power scan of satisfying b = const.in H/D plasmas reveals the r* ( m0.5) dependence of Dped at fixed density. Ip = 1.08 MA, BT = 2.4T d = 0.35 Power required to sustain the same b in H-plasma is ~2 times larger than that in D-plasma. Higher ELM frequency is observed in H-plasma. Japan Atomic Energy Agency, Naka Fusion Institute

7. * Similar profiles of ne, Te, Ti were obtained in H/D plasmas. Thus, mass effect clearly appeared in the r* profiles ( m0.5) while the profiles of b and n* were similar. Japan Atomic Energy Agency, Naka Fusion Institute

8. x = 0.2 Despite of different r* at the pedestal by mass ratio (~ 1.4), the similar edge profile are obtained in H/D plasmas. In a series of experiments, change of Dped is small in the variation of rpol* at fixed bpol (Dped  ap r*0.2). Japan Atomic Energy Agency, Naka Fusion Institute

9. Experiments on bpol dependence of Dped Power scan of satisfying bpol  Ip4 at the pedestal with controlling n  Ip4 gives the variation of bpol at fixed rpol*. Compare profiles at time slices when rpol* remains constant at the pedestal. Japan Atomic Energy Agency, Naka Fusion Institute

10. * In the peripheral region, b is varied while keeping r* and n* fixed. Japan Atomic Energy Agency, Naka Fusion Institute

11. 0.2 0.1 0.08 Dped/ap 0.06 0.04 x= 0.5 0.02 0.1 0.2 0.4 0.6 0.8 bpol When r* ( T0.5/Ip) remains constant at the pedestal, Dped becomes wider at higher bpol plasma. Appropriate power scan gives a data set with the variation of b. Then, the relation of Dped  ap b0.5 is obtained. Japan Atomic Energy Agency, Naka Fusion Institute

12. 0.12 0.1 0.08 0.06 0.04 0.02 0 0 0.02 0.04 0.06 0.08 0.1 0.12 Scaling of pedestal width D D µ µ r r * * b b 0.2 0.5 a a ped ped p p Based on the non-dimensional transport experiments using H/D plasmas, the scaling on H-mode pedestal width is obtained Rho dependence of the pedestal width is weak while it depends strongly on beta. D Dped / ap H 0.315 rpol*0.2bpol0.5 Japan Atomic Energy Agency, Naka Fusion Institute

13. Summary Conducting the H-mode experiments using hydrogen (H) and deuterium (D) discharges, dependence of pedestal width on non-dimensional parameters were examined. Similar pedestal profiles were obtained at H/D plasmas. When b is raised, pedestal width increased with a relation expressed as Dped ap r*0.2 b0.5. Japan Atomic Energy Agency, Naka Fusion Institute