Optical fiber interferometer application for high electron density measurements on compact torus plasmas

Zhang, Sen; Chen, Chen; Lan, Tao; Ding, Weixing; Zhuang, G.; Mao, Wenzhe; Lan, Shijie; Wu, Jie; Xu, Henghui; Deng, Tijian; Zhu, Jiawei; Wu, Jiadi; Zu, Yiming; Kong, Defeng; Zhang, Shoubiao; Yao, Yuan; Wei, Zhuangzhuang; Liu, Zixi; Zhou, Haiyang; Wang, Hai; Xu, Wen; Liu, Ahdi; Xie, Jinlin; Li, Hong; Xiao, C.; Liu, Wandong

doi:10.1063/5.0005868

Cited by 9 publications

(8 citation statements)

References 23 publications

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“…Thus, direct density measurements at multiple positions using interferometers will provide additional information on bulk-plasma velocity. For KTX-CTI, an optical fiber Mach-Zehnder interferometer (OFI) with the 1.55 μm laser wavelength has been developed [19]. It uses single-mode optical fibers as light carriers.…”

Section: Bench Test Setupmentioning

confidence: 99%

Development of a compact torus injection system for the Keda Torus eXperiment

Chen

Lan

Xiao

et al. 2022

Plasma Sci. Technol.

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A compact torus injection system, KTX-CTI, has been developed for the planned injection experiments on the Keda Torus eXperiment (KTX) reversed field pinch (RFP) device to investigate the physics and engineering issues associated with interaction between a compact torus (CT) and RFP. The key interests include fueling directly into the reactor center, confinement improvement, and injection of momentum and helicity into the RFP discharges. The CT velocity and mass have been measured using a multichannel optical fiber interferometer, and for the first time the time evolution of CT density profile during CT propagation is obtained. The number of injected particles, the CT velocity and density on the discharge parameters have been characterized: the maximum hydrogen CT plasma mass, m_CT, is 50 μg, corresponding to 30% of the mass in a typical KTX plasma; the CT velocity exceed 120 km/s. It is firstly observed that multiple CTs can be produced and emitted during the very short period (<100 μs) in one discharge, which is significant for the future study of repetitive CT injection, even with an ultra-high frequency.

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Section: Bench Test Setupmentioning

confidence: 99%

Development of a compact torus injection system for the Keda Torus eXperiment

Chen

Lan

Xiao

et al. 2022

Plasma Sci. Technol.

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“…The peak currents at these two regions were 310 kA and 330 kA, respectively. The line-averaged electron density was measured by the optical fiber interferometer [31] and about 100-150 × 10 20 m −3 at flat-top stage. The electron temperature is measured by Langmuir probes [8] and relatively low, only around several eV in this round experiment.…”

Section: Preliminary Experimental Results Of the Vuv Spectrometer On ...mentioning

confidence: 99%

Vacuum-Ultraviolet spectrometer system for impurity emission measurement on a Compact Torus Injection System of EAST

Shen,

Niu,

Kong

et al. 2024

J. Inst.

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Recently, a compact torus injection (CTI) system was developed for central fueling on experimental advanced superconducting tokamak (EAST). As impurity generated by the interaction between CTI plasma and the electrode material can dilute the fuel particle, it is important to measure impurity content in CTI and evaluate the effect of impurity on the plasma before the application of CTI to EAST. A vacuum-ultraviolet (VUV) spectrometer that utilizes a concave holographic grating with 1200 groove mm-1 was developed and installed on EAST-CTI for impurity emission measurement and transport study. The mainly parts of the spectrometer are an entrance slit, a concave holographic grating with 1200 groove mm-1 and a charge coupled device (CCD). The spectrometer is designed to image the spectra of 50–460 nm by turning the grating. Preliminary experimental results were obtained from the recent EAST-CTI campaign. Impurity line spectra from 50 to 460 nm wavelength range were measured and identified for several impurity species, such as iron, copper, chromium, oxygen, carbon and fluorine. For example, spectra in the intervals of 150 nm to 300 nm contained strong Fe lines. Helium spectra are also measured in the form of He I and He II spectral lines as helium is the main component of the plasma. The results show that the VUV spectrometer is capable of measuring impurity radiations on EAST-CTI and will be a useful tool for impurity behavior study.

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“…where S CT is the cross-sectional area of CT plasma, and the full-width integration of the density waveform is performed [30]. According to the time-of-flight method [31], the calculated average velocity of the CT plasma between point-1 and point-2 of the acceleration region is approximately…”

Section: Ktx-cti Bench Resultsmentioning

confidence: 99%

“…). The CT velocity in the experiment is measured by fibre optical interferometers using the time-of-flight method, which is the average velocity [31]. The first point is the average velocity between the entrance of the acceleration region and the first interferometer, while the second is the value between the first and second interferometers.…”

Section: Point Model Simulation Resultsmentioning

confidence: 99%

“…The gas delivery system is composed of eight gas valves, and the test gas is hydrogen, which is also used in this study. In the acceleration region, two sets of fibre optical interferometers are constructed (specific positions shown in figure 2) to monitor local plasma density [31]. Beyond that, the Rogowski coils, which are mainly covered on the cables, are used to measure the current in the formation and acceleration bank circuits.…”

Section: = =mentioning

confidence: 99%

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Investigation of the compact torus plasma motion in the KTX-CTI device based on circuit analyses

Dong¹,

Kong²,

Wu³

et al. 2022

Plasma Sci. Technol.

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Compact torus (CT) injection is one of the most promising methods for the central fuelling of next-generation reactor-grade fusion devices due to its high density, high velocity, and self-contained magnetised structure. A newly compact torus injector (CTI) device in Keda Torus eXperiment (KTX), named KTX-CTI, was successfully developed and tested at the University of Science and Technology in China. In this study, first, we briefly introduce the basic principles and structure of KTX-CTI, and then, present an accurate circuit model that relies on nonlinear regression analysis (NRA) for studying the current waveform of the formation region. The current waveform, displacement, and velocity of CT plasma in the acceleration region are calculated using this NRA-based one-dimensional point model. The agreement between the model results and the experimental results is better than in the previous general model results estimated by the device dimensions in previous. The next-step upgrading reference scheme of the KTX-CTI device is preliminarily investigated using this NRA-based point model. This research can provide insights for the development of experiments and future upgrades of the device.

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Optical fiber interferometer application for high electron density measurements on compact torus plasmas

Cited by 9 publications

References 23 publications

Development of a compact torus injection system for the Keda Torus eXperiment

Development of a compact torus injection system for the Keda Torus eXperiment

Vacuum-Ultraviolet spectrometer system for impurity emission measurement on a Compact Torus Injection System of EAST

Investigation of the compact torus plasma motion in the KTX-CTI device based on circuit analyses

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