Real-time control of the deposition location of ECRH in the LHD

Tsujimura, Toru Ii; Mizuno, Yoshinori; Yanai, Ryoma; Tokuzawa, T.; Ito, Y.; Nishiura, M.; Kubo, S.; Shimozuma, Τ.; Yoshimura, Y.; Igami, H.; Takahashi, H.; Tanaka, Kaoru; Yoshinuma, M.; Ohshima, S.

doi:10.1016/j.fusengdes.2020.111480

Cited by 5 publications

(6 citation statements)

References 22 publications

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“…As ECH, 77 GHz gyrotrons for the fundamental O-mode heating and 154 GHz for the second-harmonic X-mode heating are available. These are controlled by a real-time interlock system [16,17]. Note that the time duration where ECH can be turned on is limited by its technical capability and the interlock system to avoid a blank injection.…”

Section: Development Of a Collapse Avoidance Control Systemmentioning

confidence: 99%

Data-Driven Control for Radiative Collapse Avoidance in Large Helical Device

Yokoyama

Yamada

Masuzaki

et al. 2022

Plasma and Fusion Research

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A radiative collapse predictor has been developed using a machine-learning model with high-density plasma experiments in the Large Helical Device (LHD). The model is based on the collapse likelihood, which is quantified by the parameters selected by the sparse modeling, including ne , CIV, OV, and T e,edge . The control system implementing this model has been constructed with a single-board computer to apply this predictor model to the LHD experiment. The controller calculates the collapse likelihood and regulates gas-puff fueling and boosts electron cyclotron resonance heating in real-time. In density ramp-up experiments with hydrogen plasma, highdensity plasma has been maintained by the control system while avoiding radiative collapse. This result has shown that the predictor based on the collapse likelihood has the capability to predict a radiative collapse in real-time.

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Section: Development Of a Collapse Avoidance Control Systemmentioning

confidence: 99%

Data-Driven Control for Radiative Collapse Avoidance in Large Helical Device

Yokoyama

Yamada

Masuzaki

et al. 2022

Plasma and Fusion Research

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“…( 1): d ±1 = 1.38 mm for l = ±1, d ±2 = 2.75 mm for l = ±2, and d ±3 = 4.13 mm for l = ±3 at 154 GHz. The incidence angle of θ = π/4 was selected by assuming that this type of mirror will be incorporated into an existing transmission line of an electron cyclotron heating system for a 154 GHz gyrotron in the Large Helical Device, 17 where the incidence angle at a miter bend is π/4.…”

Section: A Designmentioning

confidence: 99%

Development of off-axis spiral phase mirrors for generating optical vortices in a range of millimeter waves

Tsujimura

Goto

Okada

et al. 2022

Review of Scientific Instruments

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In this paper, we report the development of off-axis spiral phase mirrors that can be used to generate optical vortices from a range of millimeter waves. An obliquely incident Gaussian beam is reflected from a spiral phase mirror and is converted into an optical vortex beam with a desired topological charge. The mirrors were fabricated by mechanical machining. The designed vortex properties of reflected waves were investigated experimentally by using a low-power test, where the designed topological charge was verified based on the interference pattern between a vortex beam and a Gaussian-like beam. The designed topological charge was also estimated by using a phase retrieval method specialized for a vortex beam. These off-axis spiral phase mirrors can be used for propagation experiments of radio frequency waves with helical wavefronts in magnetized plasma.

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“…In order to prevent the unfavorable damage of the divertor region by the transmitted wave, the interlock system for the power output from the gyrotron was developed. The interlock system constructed was based on the same system as real-time deposition location control of ECRH [12,13]. This system was controlled with real-time FPGA (field programmable gate array) processing on a Com-pactRIO made by National Instruments.…”

Section: Effectiveness Of Perpendicular Injectionmentioning

confidence: 99%

“…This system was controlled with real-time FPGA (field programmable gate array) processing on a Com-pactRIO made by National Instruments. For details, refer to the previous work [12,13]. The real-time acquisition was performed for n e,avg measured with the FIR laser interferometer and one-channel T e measured with the EC emission (ECE) diagnostic [26,27].…”

Section: Effectiveness Of Perpendicular Injectionmentioning

confidence: 99%

“…In contrast to 154 GHz ECRH, however, 77 GHz ECRH is rarely used for such transport studies at high n e due to the effect of refraction [8][9][10][11]. A real-time control system of the deposition location of ECRH was developed to mitigate the effect of refraction [12,13]. The deposition location was adjusted according to time-varying n e profiles.…”

Section: Introductionmentioning

confidence: 99%

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Improved performance of electron cyclotron resonance heating by perpendicular injection in the Large Helical Device

et al. 2020

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A real-time interlock system for power injection in electron cyclotron resonance heating (ECRH) was developed to be applied to Large Helical Device (LHD) plasma. This system enabled perpendicular injection, thus improving the performance of ECRH more than has ever been achieved before in LHD. Perpendicular propagation of the electron cyclotron wave at 77 GHz became more insensitive to the effect of refraction in comparison to the conventional oblique propagation. The achieved central electron temperature in the case of perpendicular injection was approximately 2 keV higher than that in the case of standard oblique injection for a central electron density of 1 × 1019 m−3 by 1 MW injection. With such improved performance of ECRH, high-density ECRH plasma of 8 × 1019 m−3 was successfully sustained after the injection of multiple hydrogen ice pellets for the first time in LHD.

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Real-time control of the deposition location of ECRH in the LHD

Cited by 5 publications

References 22 publications

Data-Driven Control for Radiative Collapse Avoidance in Large Helical Device

Data-Driven Control for Radiative Collapse Avoidance in Large Helical Device

Development of off-axis spiral phase mirrors for generating optical vortices in a range of millimeter waves

Improved performance of electron cyclotron resonance heating by perpendicular injection in the Large Helical Device

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