Influence of supersonic molecular beam injection on flows and turbulence in the edge plasmas on the J-TEXT tokamak

[Background]: Supersonic molecular beam injection (SMBI) is a widely used auxiliary fueling method in magnetic confinement devices, significantly influencing plasma flows and turbulence. [Purpose]: This study aims to investigate the effects of SMBI on flows and turbulence in the edge plasma of a tokamak. [Methods]: The experiment was conducted on the J-TEXT tokamak, which has a major radius of 1.05 m and a minor radius of 0.255 m. The SMBI was injected into the vacuum through one of the bottom ports. A three-step Langmuir probe array was mounted on the top of the tokamak and was employed to measure and analyze edge plasma flows and turbulence with SMBI injection. Particular attention was given to geodesic acoustic mode zonal flows (GAM), ion-ion collision frequency, turbulent Reynolds works, gradients, and turbulence-driven particle flux. [Results]: Results indicate that the GAM, turbulence, and turbulent particle flux are suppressed after SMBI, accompanying the increase in ion-ion collision frequency, and the decrease in turbulent Reynolds stress and the turbulent Reynolds work. [Conclusions]: The suppression of GAM is related to the decrease in the nonlinear driving from turbulence and the increase in collision frequency; the decrease in turbulence may be the result of the flattening of density and temperature gradients; and the reduction of turbulent heat flux may come from the drop in the fluctuations of radial velocities.

[Background]: 超声分子束注入（SMBI）是磁约束装置中广泛应用的辅助加料方法，对等离子体流与湍流具有显著影响。[Purpose]: 本研究旨在探究SMBI对托卡马克边缘等离子体流与湍流的影响。[Methods]: 实验在J-TEXT托卡马克上开展，其大半径为1.05 m，小半径为0.255 m。SMBI通过底部端口之一注入真空室。托卡马克顶部安装了三台阶朗缪尔探针阵列，用于测量和分析SMBI注入条件下的边缘等离子体流与湍流。研究重点关注测地声模带状流（GAM）、离子-离子碰撞频率、湍流雷诺功、梯度及湍流驱动粒子通量。[Results]: 结果表明，SMBI注入后，GAM、湍流及湍流粒子通量受到抑制，同时离子-离子碰撞频率升高，湍流雷诺应力与雷诺功降低。[Conclusions]: GAM的抑制与湍流非线性驱动的减弱及碰撞频率的升高相关；湍流的减弱可能源于密度与温度梯度的平坦化；而湍流热通量的降低或归因于径向速度涨落的减小。