A novel quadrature Doppler Backscattering (DBS) system has been developed and optimized for the E-band (60-90GHz) frequency range using either O-mode or X-mode polarization in DIII-D plasmas. In general, DBS measures the amplitude of density fluctuations and their velocity in the lab frame. The system can simultaneously monitor both low-frequency turbulence (f < 10MHz) and radiofrequency plasma density fluctuations over a selectable frequency range (20-500 MHz). Detection of high-frequency fluctuations has been demonstrated for low harmonics of the ion cyclotron frequency (e.g., 2fci~23MHz) and externally driven high-frequency helicon waves (f = 476MHz) using an adjustable frequency down conversion system. Importantly, this extends the application of DBS to a high-frequency spectral domain while maintaining important turbulence and flow measurement capabilities. This unique system has low phase noise, good temporal resolution (sub-millisecond) and excellent wavenumber coverage (k_θ ~ 1-20cm^{-1} and k_r ~ 20-30cm^{-1}). As a demonstration, localized internal DIII-D plasma measurements are presented from turbulence (f <= 5MHz), Alfvenic waves (f~6.5MHz), ion cyclotron waves (f >= 20MHz) as well as fluctuations around 476MHz driven by an external high-power 476 MHz helicon wave antenna. In the future, helicon measurements will be used to validate GENRAY and AORSA modeling tools for prediction of helicon wave propagation, absorption and current drive location for the newly installed helicon current drive system on DIII-D.
Conceptual study on using Doppler backscattering to measure magnetic pitch angle in tokamak plasmas
Future Energy Acceleration and Translation Programme, Agency of Science, Technology and Research (A*STAR)（未来能源加速与转化计划，科学与技术研究局）；Department of Physics, University of Oxford（牛津大学物理系）；Department of Physics and Astronomy, University of California, Los Angeles（加州大学洛杉矶分校物理与天文学系）；Lawrence Livermore National Laboratory（劳伦斯利弗莫尔国家实验室）；Department of Physics, National University of Singapore（新加坡国立大学物理系）；Commonwealth Fusion Systems（联邦聚变系统）；Princeton Plasma Physics Laboratory（普林斯顿等离子体物理实验室）；Rudolf Peierls Centre for Theoretical Physics, University of Oxford（牛津大学鲁道夫·佩尔斯理论物理中心）
Using Convolutional Neural Networks to detect Edge Localized Modes in DIII-D from Doppler Backscattering measurements
Institute of High Performance Computing (IHPC), Agency for Science, Technology and Research (A*STAR)（高性能计算研究所，科学与技术研究局）；School of Physical and Mathematical Sciences, Nanyang Technological University（南洋理工大学物理与数学科学学院）；Department of Physics and Astronomy, University of California, Los Angeles（加州大学洛杉矶分校物理与天文学系）；AIP, RIKEN（理化学研究所应用物理部）；Department of Physics, University of Oxford（牛津大学物理系）
Beam-Tracing-Based Quantitative Reconstruction of Density Fluctuations in QUEST Using Doppler Backscattering
Research Institute for Applied Mechanics, Kyushu University（九州大学应用力学研究所）；National Institute for Fusion Science（国立研究开发法人核融合科学研究所）；Future Energy Acceleration & Translation (FEAT), Agency for Science, Technology and Research (A*STAR)（科学技术研究局未来能源加速与转化中心）
A Doppler backscattering diagnostic for the EXL-50U spherical tokamak: plasma considerations and preliminary quasioptical design
A*STAR Research Entities（新加坡科学研究局）；Imperial College London（帝国理工学院）；Nanyang Technological University（南洋理工大学）；UCLA（加州大学洛杉矶分校）；ENN Science & Technology Development Co., Ltd（新奥科技发展有限公司）
Forecasting the first Edge Localized Mode (ELM) after LH-transition with a neural network trained on Doppler Backscattering data from DIII-D
Agency for Science, Technology and Research (A*STAR)（科学技术研究局）；Nanyang Technological University（南洋理工大学）；University of California, Los Angeles（加州大学洛杉矶分校）；Tohoku University（东北大学）
Comparison of DBS measurements of turbulence spectra by vertical-displacement and poloidal-angle scans using the Scotty synthetic diagnostic
Agency for Science, Technology and Research (A*STAR)（科学与技术研究局）；Nanyang Technological University（南洋理工大学）；University of California, Los Angeles (UCLA)（加州大学洛杉矶分校）
