Usoltceva Mariia, Heuraux Stéphane, Khabibullin Ildar, Faugel Helmut
Max-Planck-Institut für Plasmaphysik, Boltzmannstr. 2, 85748 Garching, Germany.
Université de Lorraine, CNRS Institut Jean Lamour, BP50840, F-54011 Nancy, France.
Rev Sci Instrum. 2022 Jan 1;93(1):013502. doi: 10.1063/5.0074838.
A novel approach for density measurements at the edge of a hot plasma device is presented-Microwave Interferometer in the Limiter Shadow (MILS). The diagnostic technique is based on measuring the change in phase and power of a microwave beam passing tangentially through the edge plasma, perpendicular to the background magnetic field. The wave propagation involves varying combinations of refraction, phase change, and further interference of the beam fractions. A 3D model is constructed as a synthetic diagnostic for MILS and allows exploring this broad range of wave propagation regimes. The diagnostic parameters, such as its dimensions, frequency, and configuration of the emitter and receiver antennas, should be balanced to meet the target range and location of measurements. It can be therefore adjusted for various conditions, and here, the diagnostic concept is evaluated on a chosen example, which was taken as suitable to cover densities of ∼10 to 10 m on the edge of the ASDEX Upgrade tokamak. Based on a density profile with a fixed radial shape, appropriate for experimental density approximation, a database of synthetic diagnostic measurements is built. The developed genetic algorithm genMILS of density profile reconstruction using the constructed database has quite low errors. It is estimated as ∼5% to 15% for density ≥10 m. Therefore, the new diagnostic technique (with a dedicated data processing algorithm) has a large potential in practical applications in a wide range of densities, with low errors in the numerical model and in the method of density reconstruction, so the total error and the density estimation accuracy are expected to be defined mostly by experimental uncertainties.
本文提出了一种用于热等离子体装置边缘密度测量的新方法——限流器阴影中的微波干涉仪（MILS）。该诊断技术基于测量切向穿过边缘等离子体、垂直于背景磁场的微波束的相位和功率变化。波的传播涉及折射、相位变化以及光束分量的进一步干涉等多种组合。构建了一个三维模型作为MILS的综合诊断工具，用于探索这种广泛的波传播模式。诊断参数，如其尺寸、频率以及发射和接收天线的配置，应进行平衡以满足测量的目标范围和位置。因此，它可以针对各种条件进行调整，在此，以一个选定的例子对诊断概念进行评估，该例子被认为适合覆盖ASDEX升级托卡马克边缘约10至10米的密度范围。基于具有固定径向形状的密度分布，适合实验密度近似，建立了一个综合诊断测量数据库。利用所构建的数据库开发的用于密度分布重建的遗传算法genMILS具有相当低的误差。对于密度≥10米，估计误差约为5%至15%。因此，这种新的诊断技术（配有专用数据处理算法）在广泛的密度范围内的实际应用中具有很大潜力，在数值模型和密度重建方法中误差较小，所以总误差和密度估计精度预计主要由实验不确定性决定。
