Development and preliminary experimental results of a high-temporal-resolution terahertz solid-source interferometer on EAST

Li, J.; Wang, S.X.; Liu, H.Q.; Mao, Wenzhe; Xie, Jing; Li, W.M.; Zhang, Y.; Chu, Yuqi; Xie, Jiawen; Zhang, J.B.; Lian, H.; Jie, Yu; Ding, W. X.

doi:10.1088/1748-0221/15/02/c02048

Cited by 8 publications

(4 citation statements)

References 8 publications

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“…It has been applied on some tokamaks like Keda Torus eXperiment (KTX) [5] and DIII-D [6]. In 2019, a single-channel 0.65 THz solid-state source interferometer was successfully developed on EAST, obtaining measurement results which are in agreement with those of the HCN laser interferometer and polarization interferometer (POINT) on EAST [7]. This paper describes the design and preliminary results of the MFCI on EXL-50, mainly including optical design, mechanical design, system layout and preliminary results, and gives a brief discussion and future plans at the end of the paper.…”

Section: Introductionmentioning

confidence: 89%

Development of a combined interferometer using millimeter wave solid state source and a far infrared laser on ENN’s XuanLong-50 (EXL-50)

Xie

Wei

Liu

et al. 2022

Plasma Sci. Technol.

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A millimeter wave solid state source - far infrared laser combined interferometer system (MFCI) consists of a three-channel 890 GHz hydrogen cyanide (HCN) laser interferometer and a three-channel 340 GHz solid state source interferometer (SSI) is developed for real-time line-integrated electron density feedback and electron density profile of the EXL-50 spherical tokamak device. The interferometer system is a Mach-Zehnder type, with all probe-channels measured vertically, covering the plasma magnetic axis to the outermost closed magnetic plane. HCN laser interferometer uses an HCN laser with a wavelength of 337 µm as the light source, and uses a rotating grating to modulate a 100 kHz beat frequency signal, giving a temporal resolution of 10 μs. The SSI uses two independent 340 GHz solid-state diode source as the light source, the frequency of the two sources is adjustable, the temporal resolution of SSI can reach 1 μs by setting the frequency difference of the two lasers at 1 MHz. The main optical path of the two interferometers is compactly installed on a set of double-layer optical platform directly below EXL-50. Dual optical path design using corner cube reflectors avoids the large support structures. Collinear the probe-beams of two wavelengths, then the phase error caused by vibration can be compensated. At present, the phase noise of the HCN Interferometer is 0.08 rad，corresponding to a line-integrated electron density of 0.88×1017m-2, one channel of line-integrated electron density was obtained by the MFCI system, and the highest density measured is about 0.7×1019m-2.

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Section: Introductionmentioning

confidence: 89%

Development of a combined interferometer using millimeter wave solid state source and a far infrared laser on ENN’s XuanLong-50 (EXL-50)

Xie

Wei

Liu

et al. 2022

Plasma Sci. Technol.

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“…As a Mach-Zehnder structured interferometer, the primary focus of data processing for a solid-state Source Interferometer (SSI) is on phase extraction [3,4]. Phase extraction includs phase demodulation and phase unwrapping.…”

Section: Data Processing Methods For Solid-state Source Interferomete...mentioning

confidence: 99%

Development of a multifunctional real-time data processing system for interferometers on EAST

Yao,

Zhang,

Liu

et al. 2023

J. Inst.

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In the latest campaign of EAST experiments, two new interferometers were installed, a dispersion interferometer (DI) based on a Carbon Dioxide laser and a solid source interferometer (SSI) based on microwave multiplier sources. To make them available for the Plasma Control System (PCS) system, each of them needs to be provided with a real-time processing system to extract the detector output signal and afterward obtain the electron density information through signal processing. To obtain interferometer data quickly and reliably, a unified hardware template was applied to both interferometers. Three main parts are included in this hardware template — digitization, digital signal processing, and output modules. In particular, the digitization section uses a multi-channel Analog-to-Digital Convertor (ADC) to acquire the signals that need to be calculated. The digital signal processing part is implemented by an FPGA, which is the hardware basis of this multifunctional template that can be used for multiple interferometers. This section includes two main parts, wrapped density signal extraction and signal unwrapping. For DI it is a phase calculation based on the intensity ratio, while for SSI it is a phase calculation by means of FFT or phase demodulation. Both computational approaches form independent IP cores to build systems quickly, while these IP cores provide parameter interfaces to adapt to different application scenarios. The output module provides a variety of data transmission methods, including fiber optic transmission and Digital-Analog-Convertor (DAC) based analog transmission, to interface with PCS or other subsequent systems. This data processing system template has been applied to each of the above two interferometers and valid data were obtained in a recent EAST experiment campaign. It demonstrates the usefulness of the template and provides a reference for the design of data processing systems on future devices.

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“…To facilitate a more comprehensive presentation of the layout of the DI system, figure 2 illustrates the optical pathway of the system with the magnetic surface profile of the plasma within EAST. Notably, the Solid-Source Interferometer (SSI) [12] 3 Experimental results and DI feedback control…”

Section: Interferometer Layout On Eastmentioning

confidence: 99%

Progress of CO₂ Dispersion Interferometer on EAST

Liu,

Li,

Liu

et al. 2024

J. Inst.

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A CO2 Dispersion Interferometer (DI) system on the Experimental Advanced Superconducting Tokamak (EAST) was successfully operated, providing plasma electron density measurements. The DI system utilizes a continuous-wave 9.3 μm CO2 laser source to measure line-averaged electron densities. This offers significant advantages, including the ability to minimize fringe jumps and insensitivity to mechanical vibrations. These characteristics are well-suited for future high-density, long-pulse plasma discharges. The DI system provides a real-time density feedback signal to the plasma control system for routine density control during long-pulse operation. Experiments with EAST demonstrated good agreement between the density obtained by the DI system and the preset densities. The DI system also exhibited stability during long-pulse discharge. Moreover, the DI system was stable during rapid density changes and high-density pellet injections. In shot No. 120594, the DI system exhibited stable density feedback during continuous projectile injection lasting over 50 seconds; the line-averaged electron density is approximately 4×1019 m-3. In contrast to the long-wavelength source interferometer, which may deflect light from the detector owing to excessive refraction angles in larger density-gradient discharges, the DI ensured accurate density measurements. The DI system on EAST is dependable for accurately measuring the electron density.

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Development and preliminary experimental results of a high-temporal-resolution terahertz solid-source interferometer on EAST

Cited by 8 publications

References 8 publications

Development of a combined interferometer using millimeter wave solid state source and a far infrared laser on ENN’s XuanLong-50 (EXL-50)

Development of a combined interferometer using millimeter wave solid state source and a far infrared laser on ENN’s XuanLong-50 (EXL-50)

Development of a multifunctional real-time data processing system for interferometers on EAST

Progress of CO₂ Dispersion Interferometer on EAST

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Development and preliminary experimental results of a high-temporal-resolution terahertz solid-source interferometer on EAST

Cited by 8 publications

References 8 publications

Development of a combined interferometer using millimeter wave solid state source and a far infrared laser on ENN’s XuanLong-50 (EXL-50)

Development of a combined interferometer using millimeter wave solid state source and a far infrared laser on ENN’s XuanLong-50 (EXL-50)

Development of a multifunctional real-time data processing system for interferometers on EAST

Progress of CO2 Dispersion Interferometer on EAST

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Product

Resources

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Progress of CO₂ Dispersion Interferometer on EAST