Conceptual design of the tangentially viewing combined interferometer-polarimeter for ITER density measurements.
Conceptual design of the tangentially viewing combined interferometer-polarimeter for ITER density measurements.
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DOI：
10.1063/1.4798602
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发表时间：
2013-04
期刊：
影响因子：
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通讯作者：
M. V. Zeeland;R. Boivin;D. Brower;T. Carlstrom;J. A. Chávez;W. Ding;Russell Feder;D. Johnson;L. Lin;R. O’Neill;C. Watts
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文献类型：
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作者：
M. V. Zeeland;R. Boivin;D. Brower;T. Carlstrom;J. A. Chávez;W. Ding;Russell Feder;D. Johnson;L. Lin;R. O’Neill;C. Watts
计划用于 ITER 中电子密度测量的系统之一是多通道切向观察组合干涉仪-旋光仪 (TIP)。这项工作讨论了设计的当前状态，包括初步的光学平台布局、校准选项、误差源和基于 CO2/CO 激光系统的性能预测。在当前设计中，在 10.59 μm 和 5.42 μm 处进行双色干涉测量，并利用旋转波技术在 10.59 μm 处进行等离子体诱导法拉第效应的单独偏振测量。偏振测量的加入提供了电子密度的独立测量，并且还可以用于校正传统双色干涉仪在所有密度下的条纹跳跃，直至格林沃尔德极限。该系统具有五个弦杆，带有独立的第一反射镜，以减少与沉积、侵蚀等相关的风险，以及一个公共的第一壁孔，以最大限度地减少穿透尺寸。对预计 ITER 基线放电的性能模拟表明，该诊断功能将与现有的反馈密度控制系统一样好，甚至更好。计算还表明，即使对于中等温度的等离子体，有限温度效应在 ITER 中也将很显着，并可能导致电子密度的显着低估。 TIP 的第二个作用是密度波动诊断；以环形阿尔文本征模为例，仿真表明 TIP 在这种能力上非常稳健，并且有可能以低至 δn∕n ≈ 10(-5) 的扰动密度解决相干模波动。
One of the systems planned for the measurement of electron density in ITER is a multi-channel tangentially viewing combined interferometer-polarimeter (TIP). This work discusses the current status of the design, including a preliminary optical table layout, calibration options, error sources, and performance projections based on a CO2/CO laser system. In the current design, two-color interferometry is carried out at 10.59 μm and 5.42 μm and a separate polarimetry measurement of the plasma induced Faraday effect, utilizing the rotating wave technique, is made at 10.59 μm. The inclusion of polarimetry provides an independent measure of the electron density and can also be used to correct the conventional two-color interferometer for fringe skips at all densities, up to and beyond the Greenwald limit. The system features five chords with independent first mirrors to reduce risks associated with deposition, erosion, etc., and a common first wall hole to minimize penetration sizes. Simulations of performance for a projected ITER baseline discharge show the diagnostic will function as well as, or better than, comparable existing systems for feedback density control. Calculations also show that finite temperature effects will be significant in ITER even for moderate temperature plasmas and can lead to a significant underestimate of electron density. A secondary role TIP will fulfill is that of a density fluctuation diagnostic; using a toroidal Alfvén eigenmode as an example, simulations show TIP will be extremely robust in this capacity and potentially able to resolve coherent mode fluctuations with perturbed densities as low as δn∕n ≈ 10(-5).