Lin Y, Nikolaeva V, Hachmeister D, Kowalski E, Reinke M L
Plasma Science and Fusion Center, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA.
Commonwealth Fusion Systems, Devens, Massachusetts 01434, USA.
Rev Sci Instrum. 2024 Aug 1;95(8). doi: 10.1063/5.0219533.
Edge scanning reflectometry (ESRL) on the SPARC tokamak aims to measure the electron density profile from the far scrape-off layer to the top of the typical H-mode pedestal and provide real-time data for plasma control. ESRL uses a standard frequency-modulated continuous wave technique from 18 to 90 GHz. By implementing both the O-mode and left-hand-cutoff X-mode, it covers densities from ∼4 × 1018 to ∼4 × 1020 m-3 at B0 ∼12 T. A voltage-controlled oscillator acts as the frequency sweep source. Phase-locked dielectric resonator oscillators and bandpass filters generate base signals ∼9-15 GHz. The signals are then frequency multiplied and amplified to reach the K (18-26 GHz), Ka (26-40 GHz), U (40-60 GHz), and E (60-90 GHz) bands. Multi-band signals are combined via the quasi-optical technique. ESRL plans to use oversized waveguides (∼20 m one-way) and a bi-static arrangement to minimize signal losses and distortions while allowing system flexibility. A COMSOL Multiphysics RF model in 2D has been set up to simulate the reflectometry process and help decide the layout of the horn antennas. Engineering analyses of the key parts of the system have been carried out in support of its preliminary design.
在斯巴达克托卡马克装置上进行的边缘扫描反射测量（ESRL）旨在测量从远刮离层到典型H模基座顶部的电子密度分布，并为等离子体控制提供实时数据。ESRL采用18至90吉赫兹的标准调频连续波技术。通过同时采用O模和左旋截止X模，它在B0约为12特斯拉时覆盖约4×10¹⁸至约4×10²⁰立方米⁻³的密度范围。一个压控振荡器作为频率扫描源。锁相介质谐振器振荡器和带通滤波器产生约9至15吉赫兹的基波信号。然后对信号进行倍频和放大，以达到K（18至26吉赫兹）、Ka（26至40吉赫兹）、U（40至60吉赫兹）和E（60至90吉赫兹）频段。多频段信号通过准光学技术进行组合。ESRL计划使用超大尺寸波导（单程约20米）和双静态布置，以尽量减少信号损失和失真，同时保证系统的灵活性。已经建立了一个二维的COMSOL Multiphysics射频模型来模拟反射测量过程，并帮助确定喇叭天线的布局。已经对该系统的关键部件进行了工程分析，以支持其初步设计。
