The Realization of a Gas Puff Imaging System on the Wendelstein 7-X Stellarator
J. L. Terry, A. von Stechow, S. G. Baek, S. B. Ballinger, O. Grulke, C. von Sehren, R. Laube, C. Killer, F. Scharmer, K. J. Brunner, J. Knauer, S. Bois, the W7-X Team
备注：
30 pages, 23 figures, submitted to Review of Scientific Instruments
A system for studying the spatio-temporal dynamics of fluctuations in the boundary of the W7-X plasma using the Gas-Puff Imaging (GPI) technique has been designed, constructed, installed, and operated. This GPI system addresses a number of challenges specific to long-pulse superconducting devices like W7-X, including the long distance between the plasma and the vacuum vessel wall, the long distance between the plasma and diagnostic ports, the range of last closed flux surface locations for different magnetic configurations in W7-X, and management of heat loads on the system's plasma-facing components. The system features a pair of "converging-diverging" nozzles for partially collimating the gas puffed locally $\approx$135 mm radially outboard of the plasma boundary, a pop-up turning mirror for viewing the gas puff emission from the side (also acting as a shutter for the re-entrant vacuum window), and a high-throughput optical system that collects visible emission resulting from the interaction between the puffed gas and the plasma and directs it along a water-cooled re-entrant tube directly onto the 8 x 16 pixel detector array of the fast camera. The DEGAS 2 neutrals code was used to simulate the H$_α$ (656 nm) and the HeI (587 nm) line emission expected from well-characterized gas-puffs of H$_2$ and He and excited within typical edge plasma profiles in W7-X, thereby predicting line brightnesses used to reduce the risks associated with system sensitivity and placement of the field of view. Operation of GPI on W7-X shows excellent signal to noise ratios (>100) over the field of view for minimally perturbing gas puffs. The GPI system provides detailed measurements of the 2-dimensional (radial and poloidal) dynamics of plasma fluctuations in the W7-X edge, scrape-off layer, and in and around the magnetic islands that make up the island divertor configuration employed on W7-X.
Global gyrokinetic analysis of Wendelstein 7-X discharge: unveiling the importance of trapped-electron-mode and electron-temperature-gradient turbulence
本文首次对类 W7-X 仿星器放电进行含动理学电子、平衡径向电场及电磁碰撞效应的非线性径向全局回旋动理学模拟，揭示芯部湍流电子热通量主要由 TEM 和 ETG 驱动，并强调有限电子温度梯度的关键作用。
Neural network predictions of plasma confinement loss in Wendelstein 7-X pellet-fueled discharges
Princeton Plasma Physics Laboratory（普林斯顿等离子体物理实验室）；Max Planck Institute for Plasma Physics（马克斯·普朗克等离子体物理研究所）；SUNY Cortland（纽约州立大学科特兰分校）；MIT Plasma Science and Fusion Center（麻省理工学院等离子体科学与聚变中心）
On the interaction between the island divertor heat fluxes, the scrape-off layer radial electric field and the edge turbulence in Wendelstein 7-X plasmas
The fixed boundary plasma equilibrium basis for a one Gigawatt electric stellarator power plant
Gauss Fusion GmbH（高斯聚变有限公司）；Karlsruhe Institute of Technology（卡尔斯鲁厄理工学院）；Technical University of Denmark（丹麦技术大学）；Research Instruments GmbH（研究仪器有限公司）；VTT Technical Research Centre of Finland Ltd.（芬兰技术研究中心有限公司）
