We report the observation of a quasi-coherent fluctuation (QCF) by the Doppler backscattering system in the scrape-off layer (SOL) region of the DIII-D tokamak. This QCF is observed in high power, high performance hybrid plasmas with near double-null divertor shape during the electron cyclotron heating period. This mode is correlated with a steepened SOL density profile, and leads to significantly elevated particle and heat fluxes between edge localized modes. The SOL QCF is a long-wavelength ion-scale fluctuation (–0.4 and ), and propagates in the ion diamagnetic direction in the plasma frame. Its radial expanse is about 1.5–2 cm, well beyond the typical width of heat flux λ _q on DIII-D. Also, the SOL QCF does not show any clear dependence on the effective SOL collisionality, and thus may raise issues on the control of plasma-material interactions in low collisionality plasmas in which the blob-induced transport is reduced. A linear simulation using BOUT++ with a five-field reduced model is performed and compared with experimental observations. In simulation results, an interchange-like density perturbation can be driven by the SOL density gradient, and its peak location and the radial width of the density perturbation are in agreement with the experimental observations.

我们报告了多普勒反向散射系统在 DIII-D 托卡马克的刮除层 (SOL) 区域中观察到的准相干涨落 (QCF)。在电子回旋加速器加热期间，在具有近双零偏滤器形状的高功率、高性能混合等离子体中观察到这种 QCF。这种模式与陡峭的 SOL 密度分布相关，并导致边缘局部模式之间的粒子和热通量显着升高。SOL QCF 是长波长离子尺度波动（–0.4 和），并在等离子体框架中沿离子抗磁方向传播。它的径向扩展约为 1.5-2 厘米，远超过热通量的典型宽度λ _q 在 DIII-D 上。此外，SOL QCF 没有表现出对有效 SOL 碰撞性的任何明显依赖，因此可能会在低碰撞性等离子体中控制等离子体 - 材料相互作用，其中 blob 诱导的传输减少。使用 BOUT++ 和五场简化模型进行线性模拟，并与实验观察进行比较。在模拟结果中，SOL密度梯度可以驱动类似互换的密度扰动，其峰值位置和密度扰动的径向宽度与实验观察一致。