A new Q-band comb-based multi-channel microwave Doppler backward scattering diagnostic developed on the HL-3 tokamak
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Ruihai TONG,
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Yu ZHOU,
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Wulyu ZHONG,
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Jie WEN,
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Zhongbing SHI,
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Xiaolan ZOU,
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Anshu LIANG,
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Zengchen YANG,
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Min JIANG,
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Xin YU,
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Yuqi SHEN
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Graphical Abstract
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Abstract
The Doppler backscattering (DBS) diagnostic is widely used to measure the localized density fluctuations and the propagation velocity of turbulent structures. Microwave is launched at a frequency that approaches a cutoff layer in the plasma at an angle oblique to the cutoff layer. A new Q-band multichannel DBS system based on a comb generator has been designed and tested for application on the HL-3 tokamak. With the comb generator and heterodyne scheme, the stability and flexibility of the new DBS system are improved. The new DBS diagnostic has a high output power (~ 10 dBm), good power flatness (< 5 dB in Q-band), and frequency stability, and the inter-frequency separation is tunable remotely. This article introduces the system design, laboratory test results, and initial experimental results from the HL-3 tokamak. With the help of the newly developed multichannel DBS, the turbulence information can be studied with high temporal and spatial resolution.
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