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To meet the demand for information on electron temperature fluctuations in low magnetic field experiments in the Large Helical Device (LHD), a new ECE radiometer covering the Q and V bands has been installed. Combination mirrors are installed in the vacuum vessel to focus the beam and efficiently propagate the radiated electron cyclotron waves. Notch filters are used to eliminate stray light from the gyrotron, and a 32-channel heterodyne radiometer is constructed using a filter bank system. As a result, oscillations of electron temperature and both electromagnetic and electrostatic fluctuations were successfully observed., source:https://doi.org/10.1051/epjconf/202327703008, identifier:0000-0001-5473-2109

We propose a combined use of a Pockels electro-optic sensor with a pickup loop coil (Bdot probe) for the measurement of magnetic fluctuations in plasmas. In this method, induced fluctuating voltage on the coil loop is converted into an optical signal by a compact electro-optic sensor in the vicinity of the measurement point and is transferred across optical fiber that is unaffected by electric noise or capacitive load issues. Compared with conventional Bdot probes, the electro-optic Bdot probe (1) is electrically isolated and free from noise pickup caused by the metallic transmission line and (2) can be operated at a higher-frequency range because of the smaller capacitance of the operation circuit, both of which are suitable for many plasma experiments. Conversely, the sensitivity of the current electro-optic Bdot probe arrangement is still significantly lower than that of conventional Bdot probes. A preliminary measurement result with the electro-optic Bdot probe showed the detection of a magnetic fluctuation signal around the cyclotron frequency range in the RT-1 magnetospheric plasma experiment., source:H. Saitoh, M. Nishiura, T. Nakazawa, J. Morikawa, Z. Yoshida, R. Osawa; Electro-optic Bdot probe measurement of magnetic fluctuations in plasma. Rev Sci Instrum 1 October 2022; 93 (10): 103540. https://doi.org/10.1063/5.0089031, source:https://doi.org/10.1063/5.0089031, identifier:0000-0001-8457-5570

The abrupt and strong excitation of the geodesic acoustic mode (GAM) has been found in the large helical device (LHD), when the frequency of a chirping energetic particle-driven GAM (EGAM) approaches twice that of the GAM frequency. The temporal evolution of the phase relation between the abrupt GAM and the chirping EGAM is common in all events. The result indicates a coupling between the GAM and the EGAM. In addition, the nonlinear evolution of the growth rate of the GAM is observed, and there is a threshold in the amplitude of the GAM for the appearance of nonlinear behavior. A threshold in the amplitude of the EGAM for the abrupt excitation of the GAM is also observed. According to one theory (Lesur et al 2016 Phys. Rev. Lett. 116 015003, Itoh et al 2016 Plasma Phys. Rep. 42 418) the observed abrupt phenomenon can be interpreted as the excitation of the subcritical instability of the GAM. The excitation of a subcritical instability requires a trigger and a seed with sufficient amplitude. The observed threshold in the amplitude of the GAM seems to correspond with the threshold in the seed, and the threshold in the amplitude of the EGAM seems to correspond with the threshold in the magnitude of the trigger. Thus, the observed threshold supports the interpretation that the abrupt phenomenon is the excitation of a subcritical instability of the GAM., source:T. Ido et al 2017 Nucl. Fusion 57 072009, source:https://doi.org/10.1088/1741-4326/aa665a

Abrupt and strong excitation of a mode has been observed when the frequency of a chirping energetic-particle driven geodesic acoustic mode (EGAM) reaches twice the geodesic acoustic mode (GAM) frequency. The frequency of the secondary mode is the GAM frequency, which is a half-frequency of the primary EGAM. Based on the analysis of spatial structures, the secondary mode is identified as a GAM. The phase relation between the secondary mode and the primary EGAM is locked, and the evolution of the growth rate of the secondary mode indicates nonlinear excitation. The results suggest that the primary mode (EGAM) contributes to nonlinear destabilization of a subcritical mode., source:Strong Destabilization of Stable Modes with a Half-Frequency Associated with Chirping Geodesic Acoustic Modes in the Large Helical Device T. Ido, K. Itoh, M. Osakabe, M. Lesur, A. Shimizu, K. Ogawa, K. Toi, M. Nishiura, S. Kato, M. Sasaki, K. Ida, S. Inagaki, S.-I. Itoh, and the LHD Experiment Group Phys. Rev. Lett. 116, 015002 – Published 8 January 2016, source:https://doi.org/10.1103/PhysRevLett.116.015002

The new findings for dynamic process of inward diffusion in the magnetospheric plasma are reported on the Ring Trap 1 (RT-1) experiment: (i) the evolution of local density profile in the self-organized process has been analyzed by the newly developed tomographic reconstruction applying a deep learning method; (ii) the impact of neutral-gas injection excites low-frequency fluctuations, which continues until the peaked density profile recovers. The fluctuations have magnetic components (suggesting the high-beta effect) which have two different frequencies and propagation directions. The phase velocities are of the order of magnetization drifts, and both the velocities and the intensities increase in proportion to the electron density. The self-regulating mechanism of density profile works most apparently in the naturally made confinement system, magnetosphere, which teaches the basic physics of long-lived structures underlying every stationary confinement scheme., source:Citation N. Kenmochi et al 2022 Nucl. Fusion 62 026041, source:https://doi.org/10.1088/1741-4326/ac412c, identifier:0000-0003-1088-8237

Alignment of the quasi-optical millimeter wave antenna for the electron cyclotron resonance heating (ECRH) can be required even after the evacuation of the vacuum vessel in fusion oriented plasma experimental devices. We developed a molybdenum millimeter wave target tile and installed it as one of the protection tiles of the vacuum vessel wall of the Large Helical Device (LHD) on the opposite side of the ECRH antennas. Inside the target tile, a sheathed thermocouple is mounted to measure the temperature increase during the millimeter wave injection toward this tile. In magnetic field configurations where neither the first nor the second electron cyclotron resonance (ECR) exists, the measured temperature increased sufficiently to be detected by the millimeter wave injection of approximately 100 kW for 0.1 s toward the target tile. Under the assumption that the distance between the target point that brings the largest temperature increase and the target point just above the thermocouple head gives the offset of the target point to be corrected, the offset of the antenna injection angle was confirmed with an accuracy of 0.4° with changing the target point shot by shot., source:https://doi.org/10.1585/pfr.16.2405066, identifier:0000-0002-4541-1757

LHDGauss is a multi-ray tracing code to calculate microwave beam propagation and power deposition of electron cyclotron heating (ECH) using the electron density and electron temperature profiles in the Large Helical Device (LHD) plasma. LHDGauss also takes into account the injected wave polarization purity. LHDGauss uses the cold plasma dispersion to calculate ray propagation and derives the power absorption profile of ECH by using the absorption coefficient based on weakly relativistic plasmas and the wave propagating perpendicularly to the magnetic field. However, the ECH beam propagation is mainly oblique to the magnetic field in the LHD and it is necessary to take into account the angular dependence of the absorption coefficient in order to derive more accurate ECH power deposition profiles. We upgraded LHDGauss and were able to calculate the absorption coefficient using the weakly relativistic dielectric tensor which considers the influence of the angle between the magnetic field and the wave vector. We compared the power deposition profiles calculated by previous and upgraded LHDGauss with the changes of the electron temperature profile of the LHD plasma in the oblique and the perpendicular O1-mode ECH injection cases. We have obtained more reasonable power deposition profiles by using the upgraded LHDGauss in both the perpendicular and the oblique injection cases., source:https://doi.org/10.1585/pfr.16.2402084, identifier:0000-0002-4501-1956

Self-organized structure formation in magnetically confined plasmas is one of the most attractive subjects in modern experimental physics. Nonequilibrium media are known to often exhibit phenomena that cannot be predicted by superposition of linear theories. One representative example of such phenomena is the hydrogen isotope effect in fusion plasmas, where the larger the mass of the hydrogen isotope fuel is the better the plasma confinement becomes, contrary to what simple scaling models anticipate. In this article, threshold condition of a plasma structure formation is shown to have a strong hydrogen isotope effect. To investigate the underlying mechanism of this isotope effect, the electrostatic potential is directly measured by a heavy ion beam probe. It is elucidated that the core electrostatic potential transition occurs with less input power normalized by plasma density in plasmas with larger isotope mass across the structure formation. This observation is suggestive of the isotope effect in the radial electric field structure formation., source:https://doi.org/10.1038/s41598-022-09526-w, identifier:0000-0001-5669-1937

A collective Thomson scattering (CTS) diagnostic with a ±3 GHz band around a 77 GHz gyrotron probe beam was developed to measure the velocity distribution of bulk and fast ions in high-temperature plasmas. We propose a new in situ calibration method for a CTS diagnostic system combined with a raytracing code. The method is applied in two situations for electron cyclotron emission in plasmas and in a CTS diagnostic with a modulated probe beam. Experimental results highlight the importance of refraction correction in probe and receive beams. The CTS spectrum is measured with the in situ calibrated CTS receiver and responds to fast ions originating from a tangential neutral beam with an energy of 170 keV and from a perpendicular beam with an energy of 60 keV, both in the large helical device. From a velocity space analysis model, the results elucidate the measured anisotropic CTS spectrum caused by fast ions. The calibration methods and analyses demonstrated here are essential for CTS, millimeter-wave diagnostics, and electron cyclotron heating required under fusion reactor conditions., source:Masaki Nishiura, Shun Adachi, Kenji Tanaka, Shin Kubo, Naoki Kenmochi, Takashi Shimozuma, Ryoma Yanai, Teruo Saito, Hideo Nuga, and Ryosuke Seki , "Collective Thomson scattering diagnostic with in situ calibration system for velocity space analysis in large helical device", Review of Scientific Instruments 93, 053501 (2022) https://doi.org/10.1063/5.0079296, source:https://doi.org/10.1063/5.0079296, identifier:0000-0002-2752-3333

We have developed a tomographic reconstruction method using a conditional Generative Adversarial Network to obtain local-intensity profiles from imaging-diagnostic data. To train the network we prepared pairs of local-emissivity and line-integrated images that simulate the experimental system. After validating the accuracy of the trained network, we used it to reconstruct a local image from a measured line-integrated image. We applied this procedure to the He II-emission imaging diagnostic for RT-1 magnetospheric plasmas, including the effects of stray light within the measured image to remove reflections from the chamber walls in the reconstruction. The local intensity profiles we obtain clearly elucidate the effect of ion-cyclotron-resonance heating. This method is a powerful tool for systems where it is difficult to solve the inversion problem due to the involved contributions of nonlocal optical effects or measurement restrictions., source:https://doi.org/10.1585/pfr.14.1202117, identifier:0000-0003-1088-8237

The Ring Trap 1 (RT-1) device creates a laboratory magnetosphere, that is motivated by the Jovian magnetosphere, which contains self-organized, high-beta plasmas. In the RT-1 plasmas, the density limit for 8.2 GHz electron cyclotron heating (ECH) occurs at the electron densities 8.0×1017 m−3 and for 2.45 GHz ECH, 1.6×1017 m−3. We have used full-wave simulations to study the propagation and absorption of electromagnetic waves in the RT-1 plasmas in an effort to understand the observed density limits as well as the over-dense state in which the actual density exceeds the cutoff density of the magnetospheric plasma. The simulation results cannot explain the experimentally observed over-dense states and density limits in the view of the power absorption. We discuss possible reasons for the gap between the experiments and the simulation results., source:https://doi.org/10.1585/pfr.14.3401134

Two-dimensional potential fluctuation profiles were measured with the heavy ion beam probe (HIBP) on the Large Helical Device. For two-dimensional measurements with HIBP, the probe beam energy had to be changed, and subtle adjustment of the beam trajectory along the long beam transport line (∼20 m) was required. An automatic beam adjustment system was developed for the beam transport line, and used to easily adjust the probe beam trajectory. Potential fluctuations in the high-frequency range (∼200 kHz) were measured, and the probe beam energy was changed shot to shot. Two-dimensional potential phase structures were successfully obtained by analyzing the coherence between potential and magnetic field fluctuation, which is used as a reference signal., source:https://doi.org/10.1585/pfr.11.2402123, identifier:0000-0003-3764-3184

Ion cyclotron range of frequencies (ICRF) heating with a frequency of a few MHz and an input power of 10 kW was applied for the first time, to the best of our knowledge, in a magnetosphere plasma device. An antenna was installed near the pole of a dipole field for slow-wave excitation. Further, a ∩-shaped antenna was implemented and characterized for efficient ion heating. Electron cyclotron heating with an input power of 8 kW sustained helium plasmas with a fill gas pressure of 3 mPa. ICRF heating was then superimposed onto the target plasma (H, D, and He). While the ICRF power was turned on, the increase in ion temperatures was observed for low-pressure helium plasmas. However, the temperature increase was not clearly observed for hydrogen and deuterium plasmas. We discuss the experimental results in terms of power absorption based on result calculated with the TASK/WF2 code., source:https://doi.org/10.1585/pfr.11.2402054, identifier:0000-0003-2410-7550

The absorption efficiency of electron cyclotron heating is investigated theoretically and experimentally to understand the wave heating mechanisms under the overdense state and the density limit. The features of self-organizing mechanisms have been observed in the dipole confinement system [M. Nishiura et al., Nucl. Fusion 55, 053019 (2015)]. The modulated 2.45 GHz electromagnetic (EM) wave is applied to the RT-1 plasmas to evaluate the EM wave's absorption efficiency from the diamagnetic signals' response. The absorption efficiency maintains a constant 100% beyond the O-mode's cutoff density. However, it decreases rapidly near the 1.6 × 1017 m−3 line-averaged density, which is twice higher than the 2.45 GHz O-mode cutoff. At less than 0.6 × 1017 m−3, the absorption efficiency simulated by a ray-tracing code in a two-dimensional model explains the experimental absorption efficiency. However, it deviates from the experimental value near the cutoff density and is more significant at the density limit. We discuss the difference between the experimental and numerical results., source:https://doi.org/10.1585/pfr.17.2405090

A decrease in the electron density is observed during high-power heating, particularly in electron cyclotron resonance heating (ECRH). One possible mechanism is the increase in the number of trapped particles, which can enhance the radial particle flux, because ECRH accelerates electrons in a direction perpendicular to the magnetic field lines. To observe the effects of the production of trapped particles, high-power (1 MW) ECRH was applied at the ripple bottom of the magnetic field strength, where trapped particles are readily produced. A rapid local outward flux of electrons was first observed near the heating position shortly after ECRH injection. The outward flux is proportional to the electron density in the density range of 0.4 × 1019 to 0.8 × 1019 m−3. The inward electron flux was subsequently enhanced in the core region., source:https://doi.org/10.1585/pfr.8.2402115

To establish a method for suppressing the spurious radiation that interferes with collective Thomson scattering measurements with less degradation of the main mode output power, the frequency evolution, and the output power of the megawatt 77-GHz gyrotron were measured during operation under optimized parameters. According to a mode competition calculation, the main mode output power may be increased by setting a lower gyrotron anode voltage at a higher magnetic field strength in the gyrotron resonator. Although the output power increased from 300 kW to 530 kW without any spurious radiation when the optimized operational parameters were used, the output power was about 50% of that at a lower magnetic field strength, and thus the output pulse width was limited to 60 ms. When an approach using the optimized operational parameters and a PIN switch was applied, the output power increased to 800 kW without any harmful spurious radiation effect and the pulse width was expanded to 2 s., source:https://doi.org/10.1585/pfr.8.2402069

0000-0001-8457-5570, We propose a combined use of a Pockels electro-optic sensor with a pickup loop coil (Bdot probe) for the measurement of magnetic fluctuations in plasmas. In this method, induced fluctuating voltage on the coil loop is converted into an optical signal by a compact electro-optic sensor in the vicinity of the measurement point and is transferred across optical fiber that is unaffected by electric noise or capacitive load issues. Compared with conventional Bdot probes, the electro-optic Bdot probe (1) is electrically isolated and free from noise pickup caused by the metallic transmission line and (2) can be operated at a higher-frequency range because of the smaller capacitance of the operation circuit, both of which are suitable for many plasma experiments. Conversely, the sensitivity of the current electro-optic Bdot probe arrangement is still significantly lower than that of conventional Bdot probes. A preliminary measurement result with the electro-optic Bdot probe showed the detection of a magnetic fluctuation signal around the cyclotron frequency range in the RT-1 magnetospheric plasma experiment.

In this study, we developed a calibration method for a fast steering antenna for investigating the mode conversion window used in electron Bernstein wave heating in the large helical device. The calibration was carried out in under-dense plasma against a line-of-sight with an optical thickness which varied spatially. Although multi-reflected background radiation becomes dominant in optically thin lines-of-sight, we succeeded in calibrating the fast steering antenna by including the effect of multi-reflected background radiation in the solution of the radiation transfer equation as the constant by which the temperature of the center of the plasma is multiplied. In addition, we report the initial results of experiments investigating the mode conversion window in over-dense plasma using the calibrated antenna., source:Yuki Goto et al 2019 Jpn. J. Appl. Phys. 58 106001, source:https://doi.org/10.7567/1347-4065/ab3e58, identifier:0000-0001-6636-8500

We have developed an ion cyclotron resonance frequency (ICRF) heating system for the Ring Trap 1 (RT-1) magnetospheric device. We excite slow waves from the polar region of the dipole magnetic field. The target helium plasma is produced by electron cyclotron heating. The electrons comprise high-temperature (>10 keV) and low-temperature (<100 eV) components with both typically exhibiting densities of the same order of magnitude. The ICRF heating causes an increase in the ion temperatures and toroidal flow velocities in the core plasma region. We observe appreciable temperature differences between the different ion species (main He+ and impurity C2+), suggesting a strong influence of the charge-exchange loss, which caused the bulk ions to remain relatively cold (~20 eV) compared to the impurity ions (~40 eV). By developing an electro-optical measurement system, we have measured the local wave electric field in the plasma., source:M. Nishiura et al 2017 Nucl. Fusion 57 086038, source:https://doi.org/10.1088/1741-4326/aa720d

Dipole plasma exhibits strong heterogeneities in field strength, density, temperature and other parameters, while maintaining a holistic balance. Our study of the internal structures reveals the fundamental self-organizing mechanisms operating in their simplest realization (as commonly observed in astronomical systems). Three new findings are reported from the RT-1 experiment. The creation of a high-energy electron core (similar to the radiation belts in planetary magnetospheres) is observed for the first time in a laboratory system. High-energy electrons (3–15 keV), produced by electron cyclotron heating, accumulate in a 'belt' located in the low-density region (high-beta value ~1 is obtained by increasing the high-energy component up to 70% of the total electrons). The dynamical process of the 'up-hill diffusion' (a spontaneous mechanism of creating density gradient) has been analyzed by perturbing the density by gas injection. The spontaneous density formation in the laboratory magnetosphere elucidates the self-organized plasma transport relevant to a planetary magnetosphere. The coherence-imaging spectroscopy visualized the two-dimensional profiles of ion temperature and flow velocity in the ion cyclotron resonance frequency heating. The ion temperature and flow were enhanced globally, and particularly along the magnetic field lines near the levitation magnet. These results advance our understanding of transport and self-organization not only in dipole plasmas, but in general magnetic confinement systems relevant to fusion plasmas., source:M. Nishiura et al 2019 Nucl. Fusion 59 096005, source:https://doi.org/10.1088/1741-4326/ab259a

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 systemenabled perpendicular injection, thus improving the performance of ECRH more than has everbeen achieved before in LHD. Perpendicular propagation of the electron cyclotron wave at77 GHz became more insensitive to the effect of refraction in comparison to the conventionaloblique propagation. The achieved central electron temperature in the case of perpendicularinjection was approximately 2 keV higher than that in the case of standard oblique injectionfor a central electron density of 1 × 1019 m−3 by 1 MW injection.With such improvedperformance of ECRH, high-density ECRH plasma of 8 × 1019 m−3 was successfullysustained after the injection of multiple hydrogen ice pellets for the first time in LHD., source:Citation T.I. Tsujimura et al 2021 Nucl. Fusion 61 026012, source:https://doi.org/10.1088/1741-4326/abc977, identifier:0000-0002-2983-5920

A six-pole Q-band waveguide filter with a notch frequency above the Q-band has been developed for plasma diagnostics. The previous paper [Nishiura et al., J. Instrum. 10, C12014 (2015)] reported that the notch frequency exists within the standard band. In this study, the newly required notch filter extends the function, which prevents a thorny wave from being mixed into an instrument beyond the standard bandwidth of the waveguide. The mode control technique for cavities realizes a deep and sharp filter shape for Q-band notch filters with 56 and 77 GHz notches, respectively. The former filter has an attenuation more than 50 dB at 56.05 GHz and a bandwidth of 1.1 GHz at −3 dB. The latter filter has an attenuation more than 55 dB at 76.95 GHz and a bandwidth of 1.6 GHz at −3 dB. The electron cyclotron emission imaging and the electron cyclotron emission (ECE) diagnostics for the Q-band implemented a pair of the fabricated filters and demonstrated the ECE measurement successfully in the intense stray radiation from a 56 GHz gyrotron., source:Review of Scientific Instruments 92, 034711 (2021); https://doi.org/10.1063/5.0041243, source:https://doi.org/10.1063/5.0041243, identifier:0000-0003-2410-7550

Coherence imaging spectroscopy (CIS) measures the two-dimensional profiles of both ion temperature and ion velocity in plasmas. The interferometric technique is realized by a certain relation between the phase and the wavelength of light emerging from a birefringent crystal. The calibration for the CIS system requires monochromatic and tunable light sources near the He II line (468.6 nm) or C III line (465 nm) where the CIS measures. In this research, the CIS system has been upgraded by implementing an electron multiplier CCD and a CIS cell. A monochromator validates the linearity of the phase relation on the wavelength near the He II line. As an in situ calibration at the Ring Trap 1 plasma device, two spectral lines of Ti and Zn lamps obtain the accurate dispersion function of phase. It is found that a simple method with two spectral lines is reliable and sufficient for the calibration., source:Review of Scientific Instruments 92, 073501 (2021); https://doi.org/10.1063/5.0043875, source:https://doi.org/10.1063/5.0043875, identifier:0000-0002-6479-049X

A new Nd:YAG laser Thomson scattering (TS) system has been developed to explore the mechanism of high-beta plasma formation in the RT-1 device. The TS system is designed to measure electron temperatures (Te) from 10 eV to 50 keV and electron densities (ne) of more than 1.0 × 1017 m−3. To measure at the low-density limit, the receiving optics views the long scattering length (60 mm) using a bright optical system with both a large collection window (260-mm diameter) and large collection lenses (300-mm diameter, a solid angle of ∼68 × 10−3 str). The scattered light of the 1.2-J Nd:YAG laser (repetition frequency: 10 Hz) is detected with a scattering angle of 90° and is transferred via a set of lenses and an optical fiber bundle to a polychromator. After Raman scattering measurement for the optical alignment and an absolute calibration, we successfully measured Te = 72.2 eV and ne = 0.43 × 1016 m−3 for the coil-supported case and Te = 79.2 eV and ne = 1.28 × 1016 m−3 for the coil-levitated case near the inner edge in the magnetospheric plasmas., source:Review of Scientific Instruments 89, 10C101 (2018); https://doi.org/10.1063/1.5037473, source:https://doi.org/10.1063/1.5037473, identifier:0000-0003-1088-8237

The direct measurements of high-frequency electric fields in a plasma bring about significant advances in the physics and engineering of various waves. We have developed an electro-optic sensor system based on the Pockels effect. Since the signal is transmitted through an optical fiber, the system has high tolerance for electromagnetic noises. To demonstrate its applicability to plasma experiments, we report the first result of measurement of the ion-cyclotron wave excited in the RT-1 magnetosphere device. This study compares the results of experimental field measurements with simulation results of electric fields in plasmas., source:Review of Scientific Instruments 88, 023501 (2017); https://doi.org/10.1063/1.4974740, source:https://doi.org/10.1063/1.4974740, identifier:0000-0003-2410-7550

A real-time control system for the deposition location of electron cyclotron resonance heating (ECRH) has been newly developed and applied to experiments on the Large Helical Device (LHD). Appropriate settings for a steerable launcher for ECRH were obtained by evaluating the deposition location and the absorption power for various electron density profiles using a ray-tracing code. The real-time deposition location control system adjusts launcher settings to improve the first-pass absorption of the refracted electron cyclotron wave, based on the ray-tracing calculations. The control system was designed to use a fast field programmable gate array (FPGA). The FPGA processes in real time the calculation of characteristic parameters regarding the density profile and the calculation of target positions requested for rotation control of a steering mirror of the launcher. The real-time deposition location control during ECRH discharges on the LHD functioned successfully in maintaining the absorption power higher than that without the control, which resulted from the deposition location maintained in the plasma core region., source:T. Ii Tsujimura, Y. Mizuno, R. Yanai, T. Tokuzawa, Y. Ito, M. Nishiura, S. Kubo, T. Shimozuma, Y. Yoshimura, H. Igami, H. Takahashi, K. Tanaka, M. Yoshinuma, S. Ohshima, Real-time control of the deposition location of ECRH in the LHD, Fusion Engineering and Design, Volume 153, 2020, 111480, source:https://doi.org/10.1016/j.fusengdes.2020.111480, identifier:0000-0002-2983-5920