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Okada, Koichi*; Kondo, Keitaro; Ochiai, Kentaro; Sato, Satoshi; Konno, Chikara; Okamoto, Atsushi*; Kobuchi, Takashi*; Kitajima, Sumio*; Sasao, Mamiko*
Journal of Plasma and Fusion Research SERIES, Vol.8, p.666 - 669, 2009/09
Measurement of fuel ion density ratio, 
/
, is required for burning control on ITER. The measured / ratio must be fed back in real time. A neutron measurement system to measure / should be operable at high counting rate. It is estimated that the number of emitted DT neutrons is 200 times higher than that of DD neutrons under the condition of ITER standard operation. A neutron measurement system was developed using a DT/DD generator, where DT neutrons are dominant and DD neutrons are contaminated slightly in the neutron beam. The measurement instrument was a TOF spectrometer. Signals originating from each neutron must be distinguished in order to measure the fuel ratio. We developed a circuit system with discrimination windows to distinguish each signal pulse, and DT and DD neutrons were measured separately and simultaneously with this system. The experimental result indicates a possibility that this system is suitable for measurement of fuel ion density ratio on ITER.
Ida, Katsumi*; Sakamoto, Yoshiteru; Yoshinuma, Mikiro*; Takenaga, Hidenobu; Nagaoka, Kenichi*; Hayashi, Nobuhiko; Oyama, Naoyuki; Osakabe, Masaki*; Yokoyama, Masayuki*; Funaba, Hisamichi*; et al.
Nuclear Fusion, 49(9), p.095024_1 - 095024_9, 2009/09
Times Cited Count：29 Percentile：72.01(Physics, Fluids & Plasmas)Dynamics of ion internal transport barrier (ITB) formation and impurity transport both in the Large Helical Device (LHD) heliotron and JT-60U tokamak are described. Significant differences between heliotron and tokamak plasmas are observed. The location of the ITB moves outward during the ITB formation regardless of the sign of magnetic shear in JT-60U and the ITB becomes more localized in the plasma with negative magnetic shear. In LHD, the low Te/Ti ratio (
1) of the target plasma for the high power heating is found to be necessary condition to achieve the ITB plasma and the ITB location tends to expand outward or inward depending on the condition of the target plasmas. Associated with the formation of ITB, the carbon density tends to be peaked due to inward convection in JT-60U, while the carbon density becomes hollow due to outward convection in LHD. The outward convection observed in LHD contradicts the prediction by neoclassical theory.
Ida, Katsumi; Sakamoto, Yoshiteru; Takenaga, Hidenobu; Oyama, Naoyuki; Ito, Kimitaka*; Yoshinuma, Mikiro*; Inagaki, Shigeru*; Kobuchi, Takashi*; Isayama, Akihiko; Suzuki, Takahiro; et al.
Physical Review Letters, 101(5), p.055003_1 - 055003_4, 2008/08
Times Cited Count：33 Percentile：79.32(Physics, Multidisciplinary)A spontaneous transition phenomena between two meta-stable states of plasmas with internal transport barrier (ITB), that are characterized by different radial profiles of second derivative of ion temperature inside the ITB region where the ion temperature gradient is large, is observed in the steady-state phase of magnetic shear in the negative magnetic shear plasma in JT-60U tokamak. The curvature asymmetry factor evaluated from the radial profile of second derivative of ion temperature profiles changes from 0.08 (symmetric curvature ITB) to -0.43 (asymmetric curvature ITB) during transition phase.
Ida, Katsumi; Sakamoto, Yoshiteru; Yoshinuma, Mikiro*; Inagaki, Shigeru*; Kobuchi, Takashi*; Matsunaga, Go; Koide, Yoshihiko
Review of Scientific Instruments, 79(5), p.053506_1 - 053506_6, 2008/05
Times Cited Count：20 Percentile：64.11(Instruments & Instrumentation)A new technique to measure the first and second derivative of the ion temperature profile has been developed using a charge exchange spectroscopy system with space modulation optics. The space observed is scanned up to 
3 cm with a cosine wave modulation frequency up to 30 Hz by shifting the object lens in front of the optical fiber bundle by 0.5 mm with a piezoelement. The first and second derivatives of ion temperature are derived from the modulation component of the ion temperature measured using Fourier analysis.
Sakamoto, Yoshiteru; Ida, Katsumi*; Yoshinuma, Mikiro*; Inagaki, Shigeru*; Kobuchi, Takashi*; Matsunaga, Go; Koide, Yoshihiko; Yoshida, Maiko; Takenaga, Hidenobu
no journal, ,
no abstracts in English
Sakamoto, Yoshiteru; Ida, Katsumi*; Yoshinuma, Mikiro*; Inagaki, Shigeru*; Kobuchi, Takashi*; Matsunaga, Go; Koide, Yoshihiko; Fujita, Takaaki; Takenaga, Hidenobu
no journal, ,
no abstracts in English
Okada, Koichi*; Kondo, Keitaro; Ochiai, Kentaro; Sato, Satoshi; Konno, Chikara; Okamoto, Atsushi*; Kobuchi, Takashi*; Kitajima, Sumio*; Sasao, Mamiko*
no journal, ,
no abstracts in English
