Plasma Turbulence Imaging via Beam Emission Spectroscopy in the Core of the DIII-D Tokamak
Plasma Turbulence Imaging via Beam Emission Spectroscopy in the Core of the DIII-D Tokamak
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DOI：
10.1585/pfr.2.s1025
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发表时间：
2007
影响因子：
0.8
通讯作者：
G. McKee;R. Fonck;D. Gupta;D. Schlossberg;M. Shafer;R. Boivin;W. Solomon
中科院分区：
文献类型：
--
作者：
G. McKee;R. Fonck;D. Gupta;D. Schlossberg;M. Shafer;R. Boivin;W. Solomon
束发射光谱仪（BES）是一种高灵敏度、高空间分辨率的成像诊断系统，已在DIII-D托卡马克上部署并于最近升级和扩展，以更好地了解等离子体湍流引起的密度波动。该系统采用5 × 6（径向×极向）矩形探测通道网格，在等离子体中平面（径向可扫描范围为0.2 < r/a ≤ 1）上对约5 × 7 cm区域的密度起伏进行成像，时间分辨率为1微秒。北京谱仪（BES）观测到了氘中性束原子碰撞诱导的多普勒频移D α荧光（λ = 652-655 nm）。诊断波数灵敏度约为k < 2。5c m −1，一个低的测量长波长（k <$ρI < 1）密度波动。最近的升级包括扩大光纤束，定制设计的高传输，锐边干涉滤光片，超快收集光学器件和放大的光电二极管探测器，这些都提供了近一个数量级的灵敏度增加相对于前一代BES系统。高灵敏度允许在归一化密度波动幅度为<$n/n <1%时观察湍流，这是核心区域波动水平的典型特征。成像阵列允许在2-3个湍流涡流尺度长度上进行采样，这捕获了涡流演化、相互作用和剪切的基本动力学。
Beam Emission Spectroscopy (BES), a high-sensitivity, good spatial resolution imaging diagnostic system, has been deployed and recently upgraded and expanded at the DIII-D tokamak to better understand density fluctuations arising from plasma turbulence. The currently deployed system images density fluctuations over an approximately 5 × 7c m region at theplasma mid-plane (radially scannable over 0.2 < r/a ≤ 1) with a 5 × 6 (radial × poloidal) grid of rectangular detection channels, with one microsecond time resolution. BES observes collisionally-induced, Doppler-shifted D α fluorescence ( λ = 652-655 nm) of injected deuterium neutral beam atoms. The diagnostic wavenumber sensitivity is approximately k⊥ < 2. 5c m −1 ,a llowing measurement of longwavelength (k⊥ρI < 1) density fluctuations. The recent upgrade in cludes expanded fiber optics bundles, customdesigned high-transmission, sharp-edge interference filters, ultra fast collection optics, and enlarged photodiode detectors that together provide nearly an order of magnitude increase in sensitivity relative to an earlier generation BES system. The high sensitivity allows visualization of turbulence at normalized density fluctuation amplitudes of ¯ n/n < 1%, typical of fluctuation levels in the core region. The imaging array allows for sampling over 2-3 turbulent eddy scale lengths, which captures the essential dynamics of eddy evolution, interaction and shearing.