ICRF Heating Experiment on LHD in Foreseeing a Future Fusion Device

Seki, T.; Mutoh, T.; Saito, Kenji; Kasahara, Hiroshi; Seki, R.; Kamio, S.; Nomura, G.; Zhao, Yanping; Wang, Sonjong

doi:10.1585/pfr.10.3405046

Cited by 5 publications

(8 citation statements)

References 10 publications

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“…LHD has demonstrated almost 48 min-long discharge with a few keV range with a MW-class heating, achieving the world record of total injected energy, 3.36 GJ [5]. LHD has explored a long-pulse operation regime towards a reactor-relevant regime while the improvement of the plasma performance (such Y. Takeiri: National Institute for Fusion Science, National Institutes of Natural Sciences, and SOKENDAI, 322-6 Oroshi, Toki 509-5292, JAPAN (email: takeiri@ nifs.ac.jp).…”

Section: Brief Overview Of Achievements In Lhd (Hydrogen Plasma Exper...mentioning

confidence: 97%

Prospect Toward Steady-State Helical Fusion Reactor Based on Progress of LHD Project Entering the Deuterium Experiment Phase

Takeiri

2018

IEEE Trans. Plasma Sci.

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Large Helical Device (LHD) is one of the world largest superconducting fusion experiment devices, having demonstrated its inherent advantage for steady-state operation since the start of experiments in 1998. LHD has also demonstrated reliable operation of the large-scale superconducting magnet system for almost two decades. Development of the challenging heating systems, such as negative-ion-based NBI, high-power and high-frequency ECH and steady-state ICH, have led to wideranging physics and engineering achievements.LHD has progressed to the next stage, that is, the deuterium experiment starting in March 2017, which should further extend plasma parameters towards reactor-relevant regime. For establishing firm basis for designing steady-state helical fusion reactor, advanced physics research, such as on isotope effect, energetic particle confinement, and plasma-wall interaction, will be intensively performed in the deuterium experiments. In an engineering aspect, the upgrade of NBI system has been carried out in preparation to the deuterium experiment, and it should contribute to future NBI development for fusion reactors including ITER. For enhancement of the particle control, the closed divertor system has been installed with pumping capability. Diagnostics for neutron measurements are newly developed and installed for the deuterium experiment.Aligned with all the progress of LHD project in terms of engineering and physics aspects, the conceptual design activity of the LHD-type helical fusion reactor, FFHR-d1, has been programmatically conducted. In parallel to the design study, engineering R&Ds for the component development have been performed, including those based on employing challenging ideas such as high-temperature superconductor, liquid metal ergodic divertor, and molten salt breeder blanket.The present status of LHD project entering the deuterium experiment phase is overviewed with putting emphasis on the engineering aspects, and then the engineering R&D activities towards steady-state helical fusion reactor are described.

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Section: Brief Overview Of Achievements In Lhd (Hydrogen Plasma Exper...mentioning

confidence: 97%

Prospect Toward Steady-State Helical Fusion Reactor Based on Progress of LHD Project Entering the Deuterium Experiment Phase

Takeiri

2018

IEEE Trans. Plasma Sci.

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“…A and B are the minimum voltage points of the upper and lower antennas, respectively (shown in figure 11), and T is the connection point between the transmission line |TC| and the conjugate-T circuit. The lengths of the two legs of the conjugate-T are |AT| = L 1 and |BT| = L 2 , respectively, which can be determined by equation (12) if two S a_minV values are obtained experimentally. We choose two S parameters, S a_minV1 and S a_minV2 from all measured S parameters.…”

Section: Optimization Of Conjugate-t For Icrh Antenna System In Lhd W...mentioning

confidence: 99%

“…To keep the reflection low with the designed conjugate-T device, we choose one S parameter, S a_minV1 , at low density, and another, S a_minV2 , at high density, and attempt to ensure that most measured S parameters exist between them. By solving equation (12), several sets of solutions can be obtained. To obtain high heating efficiency in minority ion heating, we choose a solution that ensures the current phase difference between the two points A and B of the conjugate-T circuit (figure 17) close to 180 • to excite a large parallel wave number for the HAS antennas.…”

Section: Optimization Of Conjugate-t For Icrh Antenna System In Lhd W...mentioning

confidence: 99%

“…The Large Helical Device (LHD) is a superconducting device with a R 0 (major radius) of 3.9 m, an a 0 (minor radius) of 0.6 m, an m (toroidal mode number of helical coil) of 10, an l (multipolarity) of 2 [11]. The LHD has used the poloidal array (PA), handshake form (HAS) and field-aligned-impedancetransforming (FAIT) antennas for ICRH [2,12], and a worldrecord injected energy of 3.36 GJ in a long-pulse operation was achieved [12]. To realize the goal of high-power and longpulse operation, the ICRH devices of the LHD were optimized by adopting a devised in-vessel impedance transformer (IVIT) and an ex-vessel impedance transformer (EVIT) [2].…”

Section: Introductionmentioning

confidence: 99%

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Design of an optimized load-resilient conjugate T for the ICRH system in the LHD using a novel hybrid circuit/3DLHDAP code and experimental results

Du,

Saito,

Kwak

et al. 2023

Nucl. Fusion

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It is crucial to correctly predict the S-matrix with plasma and set the optimal impedance matching device in the ion cyclotron resonance heating (ICRH) antenna system design. In this paper, a hybrid circuit/3DLHDAP code to verify the S-matrix measurements in the presence of plasma and optimize the load-resilient conjugate-T circuit for Large Helical Device (LHD) ICRH antennas has been developed and benchmarked. The variation of S-matrices for handshake form (HAS) and field-aligned-impedance-transforming (FAIT) antenna systems with density, magnetic field and coupling distance during heating obtained by the code’s simulations agrees with that of with the LHD ICRH experiments. The mutual coupling of toroidally aligned HAS antennas is larger than that of poloidally aligned FAIT antennas over a wide range of densities. When the density and coupling distance increase, under a magnetic field on the magnetic axis of 2.75 T and 1.0 T, within a certain density change range, at the position of minimum voltage with vacuum injection, the change rule of the antennas’ Sa_minV_11 and Sa_minV_22 with density is opposite to that with coupling distance, which means that under certain conditions, adjusting the coupling distance may make up for the S-parameters changes caused by plasma density variation, keeping the minimum voltage position fixed, and may make impedance matching easier to achieve during long-pulse operation. Based on obtaining the S parameters, conjugate-T circuits for the HAS and FAIT antennas are designed with the hybrid circuit/3DLHDAP code, which can keep the reflection coefficients low without controlling impedance matching device over a wide range of plasma parameters region. The related results in this paper may provide some guidance for the high-power long-pulse operation of the ICRH antenna system on the fusion device.

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“…One of the highlights of the hydrogen experiment phase has been the demonstration of a 47 min 39 s-long discharge, with a few-keV range, achieving the world record in total injected energy (3.36 GJ) [8]. The LHD has explored a world-leading long-pulse operation regime, although its fusion triple product is much lower than those of break-even tokamaks.…”

Section: Lhd Project Entering Deuterium Experiments Phasementioning

confidence: 99%

Advanced Helical Plasma Research towards a Steady-State Fusion Reactor by Deuterium Experiments in Large Helical Device

Takeiri

2018

Atoms

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The Large Helical Device (LHD) is one of the world’s largest superconducting helical system fusion-experiment devices. Since the start of experiments in 1998, it has expanded its parameter regime. It has also demonstrated world-leading steady-state operation. Based on this progress, the LHD has moved on to the advanced research phase, that is, deuterium experiment, which started in March 2017. During the first deuterium experiment campaign, an ion temperature of 10 keV was achieved. This was a milestone in helical systems research: demonstrating one of the conditions for fusion. All of this progress and increased understanding have provided the basis for designing an LHD-type steady-state helical fusion reactor. Moreover, LHD plasmas have been utilized not only for fusion research, but also for diagnostics development and applications in wide-ranging plasma research. A few examples of such contributions of LHD plasmas (spectroscopic study and the development of a new type of interferometer) are introduced in this paper.

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ICRF Heating Experiment on LHD in Foreseeing a Future Fusion Device

Cited by 5 publications

References 10 publications

Prospect Toward Steady-State Helical Fusion Reactor Based on Progress of LHD Project Entering the Deuterium Experiment Phase

Prospect Toward Steady-State Helical Fusion Reactor Based on Progress of LHD Project Entering the Deuterium Experiment Phase

Design of an optimized load-resilient conjugate T for the ICRH system in the LHD using a novel hybrid circuit/3DLHDAP code and experimental results

Advanced Helical Plasma Research towards a Steady-State Fusion Reactor by Deuterium Experiments in Large Helical Device

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