Evaluation of Efficiency of Power Transferred from ICRF Fast Ions to Bulk Plasma Based on Orbit Following in Real Coordinates in LHD

Seki, R.; Seki, T.; Watanabe, K. Y.; Kasahara, Hiroshi; Saito, Kenji; Kamio, S.; Mutoh, T.

doi:10.1585/pfr.10.1402077

Cited by 4 publications

(4 citation statements)

References 4 publications

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“…VNC2 having nine sightlines was installed in a diagonal poloidal cross-section, while VNC3 having eight sightlines was installed in a vertically elongated poloidal cross-section. Figure 11 describes the sightlines of VNC2 and VNC3 with a typical density profile of helically trapped beam ions calculated by applying the Monte-Carlo orbit following model (MORH) code [84]. Note that the VNC2 is tandemly installed using a chemical vapor deposition single-crystal diamond-based neutral particle analyzer for simultaneous measurement of neutrons and charge-exchanged energetic particles [85].…”

Section: Vncmentioning

confidence: 99%

Progress on Integrated Neutron Diagnostics for Deuterium Plasma Experiments and Energetic Particle Confinement Studies in the Large Helical Device During the Campaigns from FY2017 to FY2019

Ogawa

Isobe

Osakabe

2021

Plasma and Fusion Research

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To achieve a steady-state fusion burning plasma, energetic particle confinement studies have been performed in fusion devices. Deuterium plasma experiments in the Large Helical Device starting from March 2017 have expanded the energetic ion confinement study toward a helical-type fusion reactor. To conduct this study, integrated neutron diagnostics, such as a wide dynamic range neutron flux monitor composed of three sets of detectors, a neutron activation system with two irradiation ends, three vertical neutron cameras, four types of scintillating fiber detectors, and a fast time response neutron fluctuation detector, were installed based on the plan and were working stably, as designed. Moreover, an energetic particle confinement study was advanced by utilizing integrated neutron diagnostics. Furthermore, the results of the energetic particle confinement study using neutron diagnostics obtained from FY2017 to FY2019 are reviewed in this paper.

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Section: Vncmentioning

confidence: 99%

Progress on Integrated Neutron Diagnostics for Deuterium Plasma Experiments and Energetic Particle Confinement Studies in the Large Helical Device During the Campaigns from FY2017 to FY2019

Ogawa

Isobe

Osakabe

2021

Plasma and Fusion Research

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“…The peak position of the neutron counts changed according to the R ax . The line-integrated neutron profile is predicted by the MORH code, which is based on the Monte Carlo guiding center orbit-following models [57] using the equilibrium reconstructed by the HINT code [58]. In this calculation the birth profile of beam ions is calculated by the HFREYA code, which is a part of the FIT3D code [51].…”

Section: Study Of the Beam Ion Profilementioning

confidence: 99%

Energetic ion confinement studies using comprehensive neutron diagnostics in the Large Helical Device

et al. 2019

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Understanding of energetic particle (EP) confinement is one of the critical issues in realizing fusion reactor. In stellarator/helical devices, the research on EP confinement is one of the key topics to obtain better confinement by utilizing the flexibility of three-dimensional magnetic field. Study of EP transport in the Large Helical Device (LHD) has been performed by means of escaping EP diagnostics in hydrogen plasma operation. By starting deuterium operation of the LHD, confinement study of EPs has progressed remarkably by using newly developed comprehensive neutron diagnostics providing the information of EPs confined in the core region. The total neutron emission rate (Sn) increases due to the relatively low deviation of beam ion orbit from the flux surface with the inward shift of the magnetic axis. Sn has the peak around the electron density of 2×10 19 m -3 to 3×10 19 m -3 , as predicted. It is found that the fraction of beam-beam components in Sn is evaluated to be approximately 20% by the Fokker-Planck models TASK/FP in the plasma with both co-and counter-neutral beam injections. The equivalent fusion gain in DT plasma achieved 0.11 in a negative-ion-based neutral beam heated 2 plasma. Time evolution of Sn following the short pulse neutral beam injection into the electroncyclotron-heated low-beta plasma is reproduced by drift kinetic simulation, indicating that transport of beam ion injected by short pulse neutral beam can be described with neoclassical models in magnetohydrodynamic quiescent low-beta plasmas. The vertical neutron camera works successfully, demonstrating that in the co-neutral beam injected plasma, neutron emission profile shifts according to magnetic axis position. The shift of the neutron emission profile is reproduced by orbit-following models. The triton burnup study is performed for the first time in stellarator/heliotron so as to understand the alpha particle confinement. It is found that the triton burnup ratio, which largely increases at inward shifted configurations due to the better triton orbit and better plasma performance in inward shifted configuration is similar to that measured in tokamak having a similar minor radius with the LHD. We study the confinement capability of EPs toward a helical reactor in magnetohydrodynamic -quiescent region and expansion of the energetic-ion physics study in toroidal fusion plasmas.

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“…Figures 2(c) and (d) illustrate why a diagonal cross-section was chosen for VNC2. These figures show the line of sight for VNC1 and VNC2 and the typical beam ion density in the PNB-heated plasma, calculated using the MORH code, which is based on a five-dimensional drift kinetic model with linear Coulomb collisions [63]. The PNB primarily produces helically-trapped beam ions, which move along the valley of the helical ripple formed by two twisted coils of the LHD.…”

Section: Methodsmentioning

confidence: 99%

Energetic particle transport and loss induced by helically-trapped energetic-ion-driven resistive interchange modes in the Large Helical Device

et al. 2020

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In this work, energetic-ion confinement and loss due to energetic-ion driven magnetohydrodynamic modes are studied using comprehensive neutron diagnostics and orbit-following numerical simulations for the Large Helical Device (LHD). The neutron flux monitor is employed in order to obtain global confinement of energetic ions and two installed vertical neutron cameras (VNCs) viewing different poloidal cross-sections are utilized in order to measure the radial profile of energetic ions. A strong helically-trapped energetic-ion-driven resistive interchange mode (EIC) excited in relatively low-density plasma terminated high-temperature state in LHD. Changes in the 2 neutron emission profile due to the EIC excitation are clearly visualized by the VNCs. The reduction in the neutron signal for the helical ripple valley increases with EIC amplitude, which reaches approximately 50%. In addition to the EIC experiment, orbit-following simulations using the DELTA5D code with EIC fluctuations were performed to assess the energetic-ion transport and loss. Two-dimensional temporal evolution results show that the neutron emissivity at the helical ripple decreases significantly due to the EIC. The rapid reduction in neutron emissivity shows that the helically-trapped beam ions immediately escape from the plasma. The reduction in the VNC signals for the helical ripple valley and the total neutron emission rate increase with increasing EIC amplitude, as observed in the experiment. Calculated line-integrated neutron emission results show that the profile measured by VNC1 has one peak, whereas the profile measured by VNC2 has two peaks, as observed in the experiment. Although the neutron emission profile for VNC2 has a relatively wide peak compared with the experimental results, the significant decrease in neutron signal corresponding to the helical ripple valley was successfully reproduced.

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Evaluation of Efficiency of Power Transferred from ICRF Fast Ions to Bulk Plasma Based on Orbit Following in Real Coordinates in LHD

Cited by 4 publications

References 4 publications

Progress on Integrated Neutron Diagnostics for Deuterium Plasma Experiments and Energetic Particle Confinement Studies in the Large Helical Device During the Campaigns from FY2017 to FY2019

Progress on Integrated Neutron Diagnostics for Deuterium Plasma Experiments and Energetic Particle Confinement Studies in the Large Helical Device During the Campaigns from FY2017 to FY2019

Energetic ion confinement studies using comprehensive neutron diagnostics in the Large Helical Device

Energetic particle transport and loss induced by helically-trapped energetic-ion-driven resistive interchange modes in the Large Helical Device

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