JT-60U における慣性力を通じた回転分布の熱輸送への影響

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1 第 9 回若手科学者によるプラズマ研究会日本原子力研究開発機構那珂核融合研究所 / JT-6U における慣性力を通じた回転分布の熱輸送への影響 成田絵美 本多充 吉田麻衣子 林伸彦 浦野創 井手俊介原子力機構 This work was carried out using the HELIOS supercomputer system at InternaDonal Fusion Energy Research Centre, Aomori, Japan, under the Broader Approach collaboradon between Euratom and Japan, implemented by Fusion for Energy and JAEA.

2 Effects of toroidal rotadon direcdon on heat transport / p Toroidal rota*on: key to improve the energy confinement in tokamak plasmas Previous studies: strong E r shear Core: the strong E r shear stabilizes turbulent transport -> formadon of ITBs [H. Shirai NF999, Rewoldt NF] Pedestal: the steeper E r shear with co-toroidal rotadon > improved confinement due to rotadon [H. Urano NF8, M.Honda NF3] Recent progress: ineral effects plasma current Interplay between toroidal rotadon and flow shear is invesdgated using gyrokinedc code GKW [Y. Camenen submiced to PoP] However, the effects on heat transport in experiments are not explained yet. Ø Focus on JT-6U experiments with moderate E r shear in the core region Ø Assess the inerdal effects caused by toroidal rotadon using GKW NB ctr co rotadon velocity V φ [ m/s] co counter

3 Effects of toroidal rotadon observed in JT-6U 3/ A. ITB plasma: Steep gradient of T e -ITB with co rotadon [N. Oyama NF7] B. Convenonal H-mode plasma: Independence of core heat transport from toroidal rotadon [H. Urano NF8] A. ITB V [ m/s] φ I p /B t =.9MA/.6T B. H-mode VTCX [^ m/s]. -. I p /B t = -.6MA/.6T V φ [ m/s] V φ [ m/s] rho(tor) 8 6 T e [kev] T e [kev] steady_s63_t79_7_givenq E r [kv/m] - E r [kv/m] E r [kv/m] co rotadon counter rotadon

4 RotaDon effects in GKW / The following Vlasov equadon is solved with the Poisson eq. and Ampère s law in a rigidly rotadng frame. where grad-b drik and curvature drik Coriolis drik background potendal and centrifugal drik ü Velocity of the co-moving frame: but vanishes, is finite, as well as Ω. ü In this paper, only the Coriolis drik is considered, and the centrifugal drik is neglected.

5 Both GKW and GS show that the ITG/TEM mode is the fastest growing mode CondiDons / Miller geometry KineDc electrons Main ions & an impurity ElectromagneDc (B &B ) <k θ s < k x s = Collision (pitch-angle scacering & energy diffusion) w/o toroidal rotadon ω/(c s /a). ele./diamag. GKW. GS!. ion/diamag.!....6 k θ s.8. γ/(c s /a). GKW.3 GS ü Good agreement between GKW and GS is obtained. Re[φ] GS,..k θ s.=...6 GKW GS..! !!!! k θ s θ.[red] [rad] k θ s ~.6 gs-case6

6 RotaDon effects on the linear growth rate in the ITB plasma 6/ Velocity of the co-moving frame Ω. V φ [ m/s] co-rotadon case [ m/s] Velocity gradient Ω γ/(c s /a) = exp.. ( (. ( (... V -[ -m/s] φ Ω = Ω exp,co =-.39 s - ü If Ω, V φ at which γ becomes the maximum shiks. ΩR CondiDons: G EQDSK, KineDc electrons, Main ions & an impurity, ElectromagneDc (B &B ), k θ s =.7, k x i =, Collision (pitch-angle scacering & energy diffusion)

7 A change in the linear growth rate with the rotadon direcdon in the ITB plasma 7/ Velocity of the co-moving frame Ω γ/(c s /a) at =. for k θ s =.7 _KE_cole_beta_par_vcor_v_uprim_-_vcor.plot.txt" u :($9*.698***/3.3**/.9688):3 -domega/drho Ω [ s - ] Velocity gradient Ω V C,phi V φ [ m/s] V φ [ m/s] VTCX. -.. x..3 x x.. -x... V φ [ m/s] [ m/s] ü all cases (co, bal and ctr) have Ω <. ü co -> bal -> ctr: Increase in γ co, bal, ctr ΩR è agreement with the experiment CondiDons: G EQDSK, KineDc electrons, Main ions & an impurity, ElectromagneDc rho(tor) (B &B ), k θ s =.7, k x i =, Collision (pitch-angle scacering & energy diffusion)

8 RotaDon effects on the linear growth rate in the convendonal H-mode plasma 8/ co, ctr V φ [ m/s] ΩR [ m/s] steady_s63_t79_7_givenq Ω [ s - ] γ/(c s /a) at =. for k θ s = V φ [ m/s] ü co: Ω >, ctr: Ω < ü γ does not depend on the rotadon direcdon. è agreement with the experiment CondiDons: Miller, KineDc electrons, Main ions & an impurity, ElectromagneDc (B &B ), k θ s =.8, k x i =, Collision (pitch-angle scacering & energy diffusion)

9 V C,φ [ m/s] Ω [ s - ] RotaDon effects on the heat diffusivity in the convendonal H-mode plasma V φ [ m/s] co, ctr γ/(c s /a) at =. for k θ s =.8 V φ [ m/s] ΩR [ m/s] steady_s63_t79_7_givenq χ e /χ gb 6 3 Nonlinear simuladons are performed for the H-mode plasma. Electron heat diffusivity χ e /χ gb at =. time φ. co ctr ü Close to each other. Zonal-flow part Turbulent part k θ s 9/ co ctr

10 Conclusions and future work / p InerDal effects caused by toroidal rotadon on heat transport were examined using GKW. The qualitadve agreement with JT-6U experiments is obtained. ü ITB plasma: γ changes with the rotadon direcdon. ü Convenonal H-mode plasma: γ does not depend on the rotadon direcdon. The difference is caused by the magnitude of the rotadon velocity and its gradient. The heat diffusivides for both rotadon direcdons are close to each other. Future work Ø The change in heat diffusivity is compared between the experiments and the nonlinear simuladons for the ITB plasma parameters. Ø The effects of toroidal rotadon are verified with other discharges.