A forward modeling technique is developed for determining the characteristic features of observed MHD modes from the line-of-sight data of the soft x-ray (SXR) tomography diagnostics in the Wendelstein 7-X (W7-X) stellarator. In particular, forward modeling is used to evaluate the poloidal mode numbers m, radial location, poloidal rotation direction and ballooning character of the MHD modes. The poloidal mode structures have been modeled by the radially localized Gaussian-shaped emission regions rotating along the magnetic surfaces. In the present study the cases of rigid-shape emission regions and flexible emission regions are modeled. Various mode phase velocity dependences on the magnetic surface position are simulated. The modeled phase dynamics of line-integrated oscillations and the distribution of oscillation amplitudes are compared with the experimental signals of the SXR cameras which observe the plasma at various viewing angles in the poloidal cross-section. Application of this technique enables describing of the 1–50 kHz modes. In particular, in the discharge W7X-PID 20180918.045 three identified branches with the poloidal mode numbers m= 8, m= 10 and m= 11 localized at ρ ≈ 0.3 are rotating in the clockwise poloidal direction. The present paper reports the first application of the forward modeling technique to the data from the SXR diagnostics in W7-X. The high m-modes are identified by forward modeling in W7-X.

开发了一种正向建模技术，用于根据 Wendelstein 7-X (W7-X) 仿星器中软 X 射线 (SXR) 断层扫描诊断的视线数据确定观察到的 MHD 模式的特征特征。特别是，正向建模用于评估极向模式数mMHD 模式的径向位置、极向旋转方向和气球特征。极向模式结构已通过沿磁表面旋转的径向局部高斯形发射区域建模。在本研究中，对刚性形状发射区域和柔性发射区域的情况进行了建模。模拟了各种模式相速度对磁表面位置的依赖性。将模拟的线积分振荡的相位动力学和振荡幅度的分布与 SXR 相机的实验信号进行比较，该相机在极向截面的不同视角下观察等离子体。该技术的应用能够描述 1–50 kHz 模式。特别是，在放电 W7X-PID 20180918.045 中，三个确定的分支具有极向模式数m = 8、m = 10 和m = 11 位于ρ ≈ 0.3 以顺时针方向旋转。本文报告了前向建模技术首次应用于 W7-X 中 SXR 诊断的数据。高m模式通过 W7-X 中的正向建模来识别。