Ray-tracing analysis for combined Doppler backscattering and cross-polarization scattering diagnostic on the HL-2M tokamak

Zhou, Yu; Tong, R. H.; Zhong, W.L.; Tan, Yi; Shi, Z.B.; Jiang, M.; Wen, Jie; Yang, Z.C.; Shi, P.W.; Liang, Anshu; Yu, Xiao; Shen, Y.; Xue, Guanqun; Deng, W C

doi:10.1063/5.0126970

Review of Scientific Instruments

2023

DOI: 10.1063/5.0126970

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Ray-tracing analysis for combined Doppler backscattering and cross-polarization scattering diagnostic on the HL-2M tokamak

Yu Zhou

R. H. Tong

W.L. Zhong

et al.

Abstract: To measure plasma density and magnetic fluctuations on the HL-2M tokamak simultaneously, a new diagnostic system combining Doppler backscattering (DBS) and cross-polarization scattering (CPS) is under development. It is essential to understand the propagation of injected and scattered rays to support the electronic/quasi-optical design and subsequent interpretation of the detected signals of the multi-channel DBS/CPS measurements. Thus, ray-tracing analysis with the axisymmetric ray-tracing code BORAY has been… Show more

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Cited by 3 publications

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Quasi-optical design for the cross-polarization scattering diagnostic on the HL-3 tokamak

Zhou,

Tong,

Zhong

et al. 2024

Review of Scientific Instruments

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As the plasma beta (β) increases in high-performance tokamaks, electromagnetic turbulence becomes more significant, potentially constraining their operational range. To investigate this turbulence, a cross-polarization scattering (CPS) diagnostic system is being developed on the HL-3 tokamak for simultaneous measurements of density and magnetic fluctuations. In this work, a quasi-optical system has been designed and analyzed for the Q-band CPS diagnostic. The system includes a lens group for beam waist size optimization, a rotatable wire-grid polarizer for polarization adjustment, and a reflector group for measurement range regulation and system response enhancement. Laboratory tests demonstrated a beam radius of order 4 cm at the target measurement location (near the plasma pedestal), cross-polarization isolation exceeding 30 dB, and poloidal and toroidal angle adjustment ranges of ±40° and ±15°, respectively. These results verify the system’s feasibility through laboratory evaluations. The quasi-optical system has been installed on the HL-3 tokamak during the 2023 experimental campaign to support the development of CPS diagnostics.

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Quasi-optical design for the cross-polarization scattering diagnostic on the HL-3 tokamak

Zhou,

Tong,

Zhong

et al. 2024

Review of Scientific Instruments

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Interaction between MTM and EGAM for energy and particle confinement improvements on HL-3 tokamak

Wang,

Zou,

Duan

et al. 2024

Nucl. Fusion

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We report the first observation of microtearing mode (MTM) and its interaction with energetic-particle-induced geodesic acoustic mode (EGAM) in the reduction of ambient turbulence, leading to improvements in energy and particle confinements in electron cyclotron resonance heating (ECRH) plasma on HL-3 tokamak. MTM, observed in the magnetic fluctuation spectrum with a frequency range of 80-120 kHz, is found to be driven by the electron temperature gradient. It has been shown that MTM propagates in the electron diamagnetic drift direction with a poloidal normalized wavenumber 0.05 ≤k0ρs≤ 0.17. The n = 0, m = −2 magnetic structure of EGAM with a frequency range of 14-20 kHz is observed in the magnetic fluctuation spectrum, where n and m are the toroidal and poloidal mode numbers, respectively. The VE x B oscillation of EGAM has also been observed in the Doppler reflectometry phase derivative perturbation spectrum. The frequency of EGAM corresponds to half that of the conventional GAM. Bispectral analysis during ECRH shows pairwise interactions among EGAM, MTM and ambient turbulence (low frequency). It has been found that the reduction of ambient turbulence due to MTM and EGAM leads to the improvement of particle and energy confinements. Experimental results on HL-3 show the interaction between MTM and EGAM provides a possible way to the turbulence control for energy and particle confinement improvements in future reactors.

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A new Q-band comb-based multi-channel microwave Doppler backward scattering diagnostic developed on the HL-3 tokamak

TONG 佟,

ZHOU 周,

ZHONG 钟

et al. 2025

Plasma Sci. Technol.

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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 and at an angle that is 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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Ray-tracing analysis for combined Doppler backscattering and cross-polarization scattering diagnostic on the HL-2M tokamak

Cited by 3 publications

References 23 publications

Quasi-optical design for the cross-polarization scattering diagnostic on the HL-3 tokamak

Quasi-optical design for the cross-polarization scattering diagnostic on the HL-3 tokamak

Interaction between MTM and EGAM for energy and particle confinement improvements on HL-3 tokamak

A new Q-band comb-based multi-channel microwave Doppler backward scattering diagnostic developed on the HL-3 tokamak

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