Poloidal rotation driven by turbulent residual stress in the edge of HL-2A plasmas

doi:10.16568/j.0254-6086.201801001

Abstract

Abstract:

The first measurement of turbulent poloidal residual stress profile in the edge of tokamak plasmas is reported in this article. A specially designed reciprocating Langmuir probe array on the out mid-plane of HL-2A tokamak was used to measure turbulent momentum transport. It is observed that the residual stress is finite and opposite to diffusive stress near last closed flux surface (LCFS). Both of them are about an order of magnitude larger than Reynolds stress. These experimental results indicate that poloidal momentum sources exist at the boundary of plasma and the momentum mainly transports away with diffusion. In the region −2cm<r−r_LCFS<−0.5cm, the negative radial gradient of residual stress serves as an intrinsic torque to drive poloidal rotation.

Key words: Turbulence, Poloidal momentum transport, Poloidal rotation, Residual stress, Tokamak plasma

摘要：

首次报导了托卡马克等离子体边缘与湍流相关的极向剩余胁强剖面的测量结果。采用外中平面往复式静电探针阵列对HL-2A托卡马克边缘的极向湍流动量输运进行研究。在没有外部动量注入的欧姆放电下，剩余胁强为有限值、且其空间剖面在等离子体边缘具有明显的径向梯度，表明托卡马克等离子体边缘存在极向动量源。由动量源产生的动量主要以扩散形式向与剩余胁强相反的方向传播，最终的结果是等离子体边缘存在有限的雷诺胁强。在最后闭合磁面以内0.5~2cm区域，剩余胁强的梯度提供自发旋转的力矩，由该力矩引起的动量产生与由速度梯度引起的动量扩散共同导致了雷诺胁强出现负梯度，造成动量沉积，从而驱动极向平衡流。

关键词: 湍流, 极向动量输运, 极向旋转, 剩余胁强, 静电探针, 托卡马克等离子体

CLC Number:

TL62+2

LONG Ting, NIE Lin, KE Rui, XU Min, WU Yi-fan, GUO Dong, WANG Zhan-hui, YUAN Bo-da, GONG Shao-bo, LIU Hao, HL-2A-Team . Poloidal rotation driven by turbulent residual stress in the edge of HL-2A plasmas[J]. NUCLEAR FUSION AND PLASMA PHYSICS, 2018, 2(1): 1-7.

龙婷，聂林，柯锐，许敏*，吴一帆，郭栋，王占辉，袁博达，龚少博，刘灏，HL-2A团队. HL-2A等离子体边缘极向剩余胁强的研究[J]. 核聚变与等离子体物理, 2018, 2(1): 1-7.

References

[1] Biglari H, Diamond P H, Terry P W. Influence of sheared poloidal rotation on edge turbulence[J]. Physics of Fluids B, 1990, 2(1): 1-4.

[2] Terry P W. Suppression of turbulence and transport by sheared flow[J]. Reviews of Modern Physics, 2000, 72(1): 109-65.

[3] Yan Z, Mckee G, Fonck R, et al. Observation of the L-H confinement bifurcation triggered by a turbulence-driven shear flow in a tokamak plasma[J]. Phys. Rev. Lett., 2014, 112(12): 125002.

[4] Tynan G R, Fujisawa A, Mckee G. A review of experimental drift turbulence studies[J]. Plasma Phys. Contr. Fusion, 2009, 51(11): 113001.

[5] Diamond P, Mcdevitt C, G Rcan Ö, et al. Transport of parallel momentum by collisionless drift wave turbulence[J]. Physics of Plasmas, 2008, 15(1): 012303.

[6] Tynan G R, Schmitz L, Blush L, et al. The physics of transport barrier formation in the PBX-M H-mode[J]. Plasma Phys. Contr. Fusion, 1994, 36(7A): A285.

[7] Burrell K H. Effects of E´B velocity shear and magnetic shear on turbulence and transport in magnetic[J]. Physics of Plasmas, 1997, 4(5): 1499-518.

[8] Rice J E. Spontaneous rotation and momentum transport in tokamak plasmas[J]. Journal of Physics: Conference Series, 2008, 123(1): 012003.

[9] Rice J E, Incecushman A, Grassie J S De, et al. Inter-machine comparison of intrinsic toroidal rotation in tokamaks[J]. Nucl. Fusion, 2007, 47(11): 1618-24.

[10] La Bombard B, Rice J E, Hubbard A E, et al. Transport-driven scrape-off-layer flows and the boundary conditions imposed at the magnetic separatrix in a tokamak plasma
[J]. Nucl. Fusion, 2004, 44(10): 1047-1066.

[11] Lee W D, Rice J E, Marmar E S, et al. Observation of anomalous momentum transport in tokamak plasmas with no momentum input[J]. Phys. Rev. Lett., 2003, 91(20): 205003.

[12] Hidalgo C, Gon Alves B, Silva C, et al. Experimental investigation of dynamical coupling between turbulent transport and parallel flows in the JET plasma-boundary region[J]. Phys. Rev. Lett., 2003, 91(6): 8535-8547.

[13] Solomon W M, Burrell K H, Garofalo A M, et al. Advances in understanding the generation and evolution of the toroidal rotation profile on DⅢ-D[J]. Nucl. Fusion, 2009, 49(8): 085005.

[14] Solomon W M, Burrell K H, Degrassie J S, et al. Characterization of intrinsic rotation drive on DIII-D[J]. Nucl. Fusion, 2011, 51(7): 9.

[15] M Ller S H, Boedo J A, Burrell K H, et al. Experimental investigation of the role of fluid turbulent stresses and edge plasma flows for intrinsic rotation generation in DIII-D H-mode plasmas[J]. Phys. Rev. Lett., 2011, 106(11): 115001.

[16] Xu Y, Hidalgo C, Shesterikov I, et al. Role of symmetry-breaking induced by E_r´B shear flows on developing residual stresses and intrinsic rotation in the TEXTOR tokamak[J]. Nucl. Fusion, 2013, 53(7): 5.

[17] Waltz R E, Staebler G M, Solomon W M. Gyrokinetic simulation of momentum transport with residual stress from diamagnetic level velocity shears[J]. Physics of Plasmas, 2011, 18(4): 332-339.

[18] Rice J E. Experimental observations of driven and intrinsic rotation in tokamak plasmas[J]. Plasma Phys. Contr. Fusion, 2016, 58(8): 083001.

[19] Kaang H H, Jhang H, Singh R, et al. Enhancement of residual stress by electromagnetic fluctuations: a quasi-linear study[J]. Physics of Plasmas, 2016, 23(5): 9.

[20] Grierson B A, Wang W X, Ethier S, et al. Main-ion intrinsic toroidal rotation profile driven by residual stress torque from ion temperature gradient turbulence in the DIII-D tokamak
[J]. Phys. Rev. Lett., 2017, 118(1): 5.

[21] Yan Z, Xu M, Diamond P H, et al. Intrinsic rotation from a residual stress at the boundary of a cylindrical laboratory plasma[J]. Phys. Rev. Lett., 2010, 104(6): 065002.

[22] Diamond P H, Mcdevitt C J, G Rcan Ö D, et al. Physics of non-diffusive turbulent transport of momentum and the origins of spontaneous rotation in tokamaks[J]. Nucl. Fusion, 2009, 49(4): 571-576.

[23] Hahm T S, Diamond P H, Gurcan O D, et al. Nonlinear gyrokinetic theory of toroidal momentum pinch[J]. Physics of Plasmas, 2007, 14(7): 072302.

[24] Manz P, Xu M, Fedorczak N, et al. Spatial redistribution of turbulent and mean kinetic energy[J]. Physics of Plasmas, 2012, 19(1): 012309.

[25] Zhao K J, Lan T, Dong J Q, et al. Toroidal symmetry of the geodesic acoustic mode zonal flow in a tokamak plasma[J]. Phys. Rev. Lett., 2006, 96(25): 255004.

[26] Lan T, Liu A D, Yu C X, et al. Spectral characteristics of geodesic acoustic mode in the HL-2A tokamak[J]. Plasma Phys. Contr. Fusion, 2008, 50(4): 045002.

[27] Xu M, Duan X R, Dong J Q, et al. Overview of recent HL-2A experiments[J]. Nucl. Fusion, 2015, 55(10): 104022.

[28] Peeters A G, Angioni C, Strintzi D. Toroidal momentum pinch velocity due to the coriolis drift effect on small scale instabilities in a toroidal plasma[J]. Phys. Rev. Lett., 2007, 98(26): 265003.

[29] Chankin A V, Mccracken G M. Loss ion orbits at the tokamak edge[J]. Nucl. Fusion, 1993, 33(10): 1459.