Analysis of wall-embedded Langmuir probe signals in different conditions on the Tokamak à Configuration Variable.
Analysis of wall-embedded Langmuir probe signals in different conditions on the Tokamak à Configuration Variable.
复制标题
在托卡马克配置变量上不同条件下分析壁埋朗缪尔探针信号。
DOI：
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发表时间：
2018
影响因子：
1.6
通讯作者：
A. Baillod
中科院分区：
文献类型：
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作者：
O. Février;C. Theiler;H. D. Oliveira;B. Labit;N. Fedorczak;A. Baillod
本文介绍了安装在托卡马克TCV上的电流壁嵌入式朗缪尔探针系统，以及用于解释探针在扫频偏置条件下工作时获得的电流-电压特性的分析工具链。该分析是基于一个四参数拟合结合最低温度的方法。为了减少等离子体波动和测量噪声的影响，通常在进行拟合之前对几个电流-电压特性进行平均。这个过程对结果的影响进行了研究，以及在电路中的有限电阻，这可能会导致高估的温度可能发挥的作用。我们研究的应用程序中的一个特定的制度，等离子体脱离，从其他诊断的结果表明，来自朗缪尔探针的电子温度可能被高估。为了解决这个问题，我们探索其他拟合模型，特别是扩展的非对称双探头拟合，其特点是鞘扩张的影响。我们表明，这些模型产生较低的温度（高达约60%）比标准分析在分离的条件下，特别是对于观察到的等离子体撞击点附近的温度峰值，但与其他测量仍然存在差异。我们探讨了一个可能的解释，这种观察，一个快速的电子人口的存在，并评估如何强大的不同的方法是在这种条件下。
This paper presents the current wall-embedded Langmuir probe system installed on the Tokamak à Configuration Variable (TCV), as well as the analysis tool chain used to interpret the current-voltage characteristic obtained when the probes are operated in swept-bias conditions. The analysis is based on a four-parameter fit combined with a minimum temperature approach. In order to reduce the effect of plasma fluctuations and measurement noise, several current-voltage characteristics are usually averaged before proceeding to the fitting. The impact of this procedure on the results is investigated, as well as the possible role of finite resistances in the circuitry, which could lead to an overestimation of the temperature. We study the application of the procedure in a specific regime, the plasma detachment, where results from other diagnostics indicate that the electron temperature derived from the Langmuir probes might be overestimated. To address this issue, we explore other fitting models and, in particular, an extension of the asymmetric double probe fit, which features effects of sheath expansion. We show that these models yield lower temperatures (up to approximately 60%) than the standard analysis in detached conditions, particularly for a temperature peak observed near the plasma strike point, but a discrepancy with other measurements remains. We explore a possible explanation for this observation, the presence of a fast electron population, and assess how robust the different methods are in such conditions.