HL-2A等离子体边缘极向剩余胁强的研究

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

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。

The first measurement of turbulent poloidal residual stress profile in the edge of tokamak plasmas is reported in this article. A specially designed reciprocating Langrnuir 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-rLCFS〈-0.5cm, the negative radial gradient of residual stress serves as an intrinsic torque to drive poloidal rotation.