[en] The D-T fusion plasma experiments have been performed since November 1993 on TFTR. Tritium was introduced to the torus by gas puffing and/or by neutral beam injection (NBI). As auxiliary heatings, the NBI heating and ion cyclotron range of frequency (ICRF) heating were provided. The D-T neutron energy spectra were obtained for 'NBI and ICRF' heated plasmas and for NBI heated plasmas. These were the first D-T neutron spectra obtained from D-T plasmas in the world. The full width at half maximum (FWHM) of the peak for the ICRF heated plasma is wider than that for NBI heated plasma. The calculated energy spectra suggested this broadening was due to the existence of the high energy tritium ion tail of 100-400keV. Space resolved measurements of D-T neutron energy spectra will be necessary for ICRF heated D-T plasma experiments on the next large tokamak, such as ITER, to evaluate the mechanism of ICRF heating in the plasma. The counter telescope with thick radiator (COTETRA) will be a suitable diagnostic for this purpose because of its good energy resolution and compactness. (J.P.N.) 74 refs

[en] A new kind of energetic particle driven geodesic acoustic mode (EGAM) is investigated using a hybrid simulation code for energetic particles interacting with a magnetohydrodynamic fluid. The energetic particle charge exchange and inertia are considered, and the new EGAM, which has weak bulk plasma temperature dependence of frequency in LHD, is reproduced by simulation. By contrast, the traditional EGAM frequency is proportional to the square root of bulk plasma temperature. Three conditions are found to be important for the transition from the traditional EGAM to the new EGAM: 1) high energetic particle pressure, 2) high charge exchange rate, and 3) low bulk plasma density. A new resonance condition that ω_E_G_A_M=(1/K)ω_θ is obtained, where 1 and K are arbitrary integers. 1/K=2/3 and 1/K=3/5 for most counter- and co-going particles, respectively. The counter-going particles are more dominant for resonance. In addition, it is found that the new EGAM is a kind of typical energetic particle mode (EPM). (author)

[en] As for the Large Helical Device (LHD), the authors are promoting research on the high-performance plasma using deuterium gas for the purpose of accumulating databases related to helical type fusion reactor design, building academic foundations, developing new research areas, and expanding the diversity of experiments. At the start of the deuterium experiment, they improved and expanded the performance of the LHD main unit, heating equipment, measuring equipment, etc. and newly developed the neutron measuring equipment, which symbolizes the deuterium experiment. In addition, prior to the deuterium experiment, they developed various analysis codes necessary for understanding the deuterium plasma together with collaborators in Japan and overseas, and these codes are currently widely used in experimental analysis. This paper gives an overview of the facilities, equipment, and analysis codes prepared for the deuterium experiments, and touches on typical research results, too. (A.O.)

[en] Additional heating of ctr-injected neutral beam was applied to the co-based High-T_i mode scenario plasma. The energy deposition by neutral beam was estimated for co-injected and co/ctr-injected cases at the plasma center. The analysis indicates that the ion temperature is strongly correlates with the energy deposition from fast ions to a single bulk ion. The analysis suggests that reduction of the fast ion loss is effective to increase ion temperature. (author)

[en] Two positive-ion-based neutral injectors for Large Helical Device (LHD), which are LHD-NBI no.4 and no.5, are overviewed. Those injectors are installed to enhance the ion temperature of LHD plasmas by producing low-temperature ions. Each beamline has four ion sources, and the injection power of NBI no.4 is 6 MW at the energy of 40 keV. The NBI no.5 is designed to provide the beam power of 6 MW at 45 keV for hydrogen beam and 9 MW at 80 keV for deuterium beam. Beam injection with NBI no.4 has started with two ion sources in 2004 and with full of four sources in 2005. The maximum power of NBI no.4 has reached 7 MW. The injector contributes to increase ion temperature, and is also applied to a diagnostic beam using charge exchange recombination spectroscopy (CXRS). The NBI no.5 has been operational in 2010. After tuning a ratio of acceleration and deceleration voltages, the injection power reaches 5.8 MW at 40 keV so far. (author)

[en] High power heating experiments combining electron cyclotron heating (ECH) and neutral injection beam (NBI) are performed with two gyrotrons and two neutral beam injectors. The classical effect to increase the effective energy input from neutral beam to ions and from electron to ions by increasing the electron temperature is expected. In addition to this classical effect, the change in the potential structure which can be stimulated by adding ECH is expected to change the high energy and/or bulk ion confinement. The results from this high power heating experiment are reported. (author)

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[en] 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. (author)

[en] The measurement of effective ion charge Z_eff in LHD is reconsidered. The plasma equilibrium database, the so-called TSMAP, recently made available is used for mapping of locations on the line-of-sight on the effective minor radius r_eff so that accuracy of the electron temperature and density profiles for evaluating the Bremsstrahlung intensity has been improved. The influence of impurity lines is also estimated from other diagnostic data, and it is demonstrated that unrealistically large Z_eff values derived with the conventional method for low density plasmas are avoidable. (author)