E×B Flux Driven Detachment Bifurcation in the DIII-D Tokamak.
E×B Flux Driven Detachment Bifurcation in the DIII-D Tokamak.
复制标题
DOI：
10.1103/physrevlett.121.075001
复制
发表时间：
2018-08
影响因子：
8.6
通讯作者：
A. Jaervinen;S. Allen;D. Eldon;M. Fenstermacher;M. Groth;D. N. Hill-D. N.-Hill-2252413176;A. Leonard;A. McLean
中科院分区：
文献类型：
--
作者：
A. Jaervinen;S. Allen;D. Eldon;M. Fenstermacher;M. Groth;D. N. Hill-D. N.-Hill-2252413176;A. Leonard;A. McLean
在DIII-D托卡马克等离子体中，随着密度的增加，实验观察到从低密度、高温、附着导流器条件到高密度、低温、分离导流器条件的分岔阶跃转变。只有在高约束模式下，当bx∇B漂移指向分流器时，才能观察到阶跃跃迁。这项工作首次报道了理论解释和数值模拟，定性地再现了这种分岔及其对环面场方向的依赖。根据该模型，分叉主要是由E×B-drift通量、导流器电位结构和导流器条件的相互依赖驱动的。在附图条件下，低场侧（LFS）导流器的强电位梯度驱动E×B-drift通量向高场侧导流器流动，强化了LFS导流器支路的低密度、高温条件。在脱离开始时，LFS分流器腿电位梯度的降低也降低了E×B-drift通量，使得分流器等离子体非线性地发展到高密度、强烈分离的状态。基于导流器汤姆森散射测量的E×B-drift通量的实验估计及其对导流器条件的依赖与数值预测在质量上是一致的。讨论了对下一步聚变装置引流器功率排气和分离控制的意义。
A bifurcative step transition from low-density, high-temperature, attached divertor conditions to high-density, low-temperature, detached divertor conditions is experimentally observed in DIII-D tokamak plasmas as density is increased. The step transition is only observed in the high confinement mode and only when the B×∇B drift is directed towards the divertor. This work reports for the first time a theoretical explanation and numerical simulations that qualitatively reproduce this bifurcation and its dependence on the toroidal field direction. According to the model, the bifurcation is primarily driven by the interdependence of the E×B-drift fluxes, divertor electric potential structure, and divertor conditions. In the attached conditions, strong potential gradients in the low field side (LFS) divertor drive E×B-drift flux towards the high field side divertor, reinforcing low density, high temperature conditions in the LFS divertor leg. At the onset of detachment, reduction in the potential gradients in the LFS divertor leg reduce the E×B-drift flux as well, such that the divertor plasma evolves nonlinearly to high density, strongly detached conditions. Experimental estimates of the E×B-drift fluxes, based on divertor Thomson scattering measurements, and their dependence on the divertor conditions are qualitatively consistent with the numerical predictions. The implications for divertor power exhaust and detachment control in the next step fusion devices are discussed.