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Journal Articles

ITPA (International Tokamak Physics Activity) meeting report, 53

Kawano, Yasunori; Akiyama, Tsuyoshi*; Ishikawa, Masao; Isobe, Mitsutaka*; Itami, Kiyoshi; Ejiri, Akira*; Peterson, B.*

Purazuma, Kaku Yugo Gakkai-Shi, 92(2), P. 145, 2016/02

no abstracts in English

Journal Articles

ITPA (International Tokamak Physics Activity) meeting report, 50

Kawano, Yasunori; Akiyama, Tsuyoshi*; Ishikawa, Masao; Isobe, Mitsutaka*; Itami, Kiyoshi; Ejiri, Akira*; Peterson, B.*

Purazuma, Kaku Yugo Gakkai-Shi, 91(8), P. 565, 2015/08

no abstracts in English

Journal Articles

ITPA (International Tokamak Physics Activity) meeting report, 48

Kawano, Yasunori; Akiyama, Tsuyoshi*; Ishikawa, Masao; Isobe, Mitsutaka*; Itami, Kiyoshi; Ejiri, Akira*; Peterson, B. J.*

Purazuma, Kaku Yugo Gakkai-Shi, 91(1), P. 76, 2015/01

no abstracts in English

Journal Articles

A Study on fast digital discrimination of neutron and $$gamma$$-ray for improvement neutron emission profile measurement

Uchida, Yuki*; Takada, Eiji*; Fujisaki, Akihiro*; Isobe, Mitsutaka*; Ogawa, Kunihiro*; Shinohara, Koji; Tomita, Hideki*; Kawarabayashi, Jun*; Iguchi, Tetsuo*

Review of Scientific Instruments, 85(11), p.11E118_1 - 11E118_4, 2014/11

 Times Cited Count:6 Percentile:33.97(Instruments & Instrumentation)

Journal Articles

ITPA (International Tokamak Physics Activity) meeting report, 46

Kawano, Yasunori; Akiyama, Tsuyoshi*; Ishikawa, Masao; Isobe, Mitsutaka*; Itami, Kiyoshi; Ejiri, Akira*; Peterson, B.*

Purazuma, Kaku Yugo Gakkai-Shi, 90(7), P. 431, 2014/07

no abstracts in English

Journal Articles

Fast neutron-$$gamma$$ discrimination on neutron emission profile measurement on JT-60U

Ishii, Keiichi*; Shinohara, Koji; Ishikawa, Masao; Baba, Mamoru*; Isobe, Mitsutaka*; Okamoto, Atsushi*; Kitajima, Sumio*; Sasao, Mamiko*

Review of Scientific Instruments, 81(10), p.10D334_1 - 10D334_3, 2010/10

 Times Cited Count:6 Percentile:33.58(Instruments & Instrumentation)

Journal Articles

Escaping ion measurement with high time resolution during bursting modes induced by neutral beam injection on CHS

Shinohara, Koji; Isobe, Mitsutaka*; Darrow, D. S.*; Shimizu, Akihiro*; Nagaoka, Kenichi*; Okamura, Shoichi*

Plasma and Fusion Research (Internet), 2, p.042_1 - 042_8, 2007/09

Journal Articles

Neutron emission profile measurement and fast charge exchange neutral particle flux measurement for transport analysis of energetic ions in JT-60U

Ishikawa, Masao; Nishitani, Takeo; Kusama, Yoshinori; Sukegawa, Atsuhiko; Takechi, Manabu; Shinohara, Koji; Krasilnikov, V. A.*; Kaschuck, Y.*; Sasao, Mamiko*; Isobe, Mitsutaka*; et al.

Plasma and Fusion Research (Internet), 2, p.019_1 - 019_11, 2007/05

no abstracts in English

Journal Articles

Confinement degradation of energetic ions due to Alfv$'e$n eigenmodes in JT-60U negative-ion-based neutral beam injection plasmas

Ishikawa, Masao; Takechi, Manabu; Shinohara, Koji; Matsunaga, Go; Kusama, Yoshinori; Fukuyama, Atsushi*; Krasilnikov, V. A.*; Kashuck, Yu.*; Nishitani, Takeo; Morioka, Atsuhiko; et al.

Proceedings of 21st IAEA Fusion Energy Conference (FEC 2006) (CD-ROM), 8 Pages, 2007/03

Confinement degradation of energetic ions due to Alfv$'e$n Eigenmodes (AEs) induced by negative-ion-based neutral beam injection for the classical confinement is quantitatively evaluated for the first time. AEs, whose frequency largely sweep with the time scale of a few hundreds millisecond as the minimum value of the safety factor decrease, have been observed in JT-60U. These mode behavior can be explained by reversed-shear induced AEs (RSAEs). Measured total neutron emission rate (Sn) in the presence of the AEs is compared with that predicted by a classical theory. As a result, confinement degradation of energetic ions is confirmed, Line-integrated neutron emission profile is also compared with that predicted when assuming that the confinement is classical. The result indicates energetic ions are transported from core region of the plasma due to these AEs. Further, changes in energy distribution of charge exchange neutral fluxes suggest radial transport is due to the resonance interaction between energetic ions and AEs.

Journal Articles

Studies of fast-ion transport induced by energetic particle modes using fast-particle diagnostics with high time resolution in CHS

Isobe, Mitsutaka*; Toi, Kazuo*; Matsushita, Hiroyuki*; Goto, Kazuyuki*; Suzuki, Chihiro*; Nagaoka, Kenichi*; Nakajima, Noriyoshi*; Yamamoto, Satoshi*; Murakami, Sadayoshi*; Shimizu, Akihiro*; et al.

Nuclear Fusion, 46(10), p.S918 - S925, 2006/10

 Times Cited Count:27 Percentile:69.39(Physics, Fluids & Plasmas)

no abstracts in English

Journal Articles

Observation of confinement degradation of energetic ions due to Alfv$'e$n eigenmodes in JT-60U weak shear plasmas

Ishikawa, Masao; Takechi, Manabu; Shinohara, Koji; Kusama, Yoshinori; Matsunaga, Go; Krasilnikov, V. A.*; Kashuck, Y.*; Isobe, Mitsutaka*; Nishitani, Takeo; Sukegawa, Atsuhiko; et al.

Nuclear Fusion, 46(10), p.S898 - S903, 2006/10

 Times Cited Count:13 Percentile:44.28(Physics, Fluids & Plasmas)

Confinement degradation of energetic ions due to Alfv$'e$n eigenmodes (AEs) has been investigated with negative ion based neutral beam injection into JT-60U weak shear plasmas. AEs with a rapid frequency sweeping and then saturation as the minimum value of the safety factor decreases have been observed. This frequency behaviour can be explained by RSAE and the transition from RSAEs toTAEs. The associated change in the charge exchange neutral particle flux suggests energetic ion transport due to these AEs. The total neutron emission reduction rate in the presence of these AEs is evaluated by calculation using the orbit following Monte-Carlo code taking into account the change in bulk plasmas. The evaluation indicates confinement of energetic ions is degraded due to these AEs. In particular, it is found that the confinement degradation of energetic ions is maximum during the transition from RSAEs to TAEs.

Journal Articles

Escaping ion measurement with high time resolution on CHS

Shinohara, Koji; Isobe, Mitsutaka*; Darrow, D. S.*

Review of Scientific Instruments, 77(10), p.10E521_1 - 10E521_4, 2006/10

 Times Cited Count:4 Percentile:26.54(Instruments & Instrumentation)

A scintillator probe can measure the temporal evolution of both the gyro-radius and the pitch angle of the escaping ions with relatively large energy. On this system, the time resolution of the 2D measurement is determined by a framing rate of the camera. The framing rate of the old camera was 60Hz, thus the time resolution was about 17 ms. Our interest is to understand the energetic ion transport in fast events such as a bursting Alfv$'e$n eigenmode. The typical time scale of these event interested is less than a few ms. The time resolution of the old camera was not enough for this purpose. The FASTCAM ultima II, which is a product of Photron Co., is an image-intensified high-speed video camera system with the ability to record up to 13,500 frames per second. By replacing the old camera with this ultima II, the temporal resolution was improved from about 17 ms to 0.075 ms. We have successfully installed the fast camera and captured some fast events caused by MHDs, which was not observed by the old camera. Here, we will present the specification of this system and the preliminary results using this fast camera.

Journal Articles

Energetic ion measurements using a directional probe

Nagaoka, Kenichi*; Isobe, Mitsutaka*; Shinohara, Koji; Osakabe, Masaki*; Shimizu, Akihiro*; Okamura, Shoichi*

Plasma and Fusion Research (Internet), 1(1), p.005_1 - 005_2, 2006/01

A directional Langmuir probe (DLP) method has been applied for energetic particles (ions) measurement in a magnetically confined plasma. Two experimental demonstrations have been performed in the compact helical system (CHS). One is neutral beam modulation experiment and the other is the measurement of energetic ion loss induced by MHD bursts. The results of the DLP are consistent with that of a neutral particle analyzer (NPA) and a lost ion probe (LIP). These experiments show that this method is applicable outside and also inside of the last closed flux surface.

Journal Articles

Energetic ion transport by abrupt large-amplitude event induced by negative-ion-based neutral beam injection in the JT-60U

Ishikawa, Masao; Takechi, Manabu; Shinohara, Koji; Kusama, Yoshinori; Cheng, C. Z.*; Matsunaga, Go; Todo, Yasushi*; Gorelenkov, N. N.*; Kramer, G. J.*; Nazikian, R. M.*; et al.

Nuclear Fusion, 45(12), p.1474 - 1480, 2005/12

 Times Cited Count:37 Percentile:76.55(Physics, Fluids & Plasmas)

To investigate energetic ion transport induced by Alfven eigenmodes (AEs) the neutron emission profile measurement and the charge exchange (CX) neutral particle flux measurement by Natural Diamond Detector has been performed simultaneously in the JT-60U for the first time. The energetic ion profiles inferred from these measurements indicate that ALEs cause a radial redistribution of energetic ions of limited energy range from the core region to the outer region of the plasma in weak shear plasmas. This energy range is consistent with the resonance condition between the mode and the energetic ions. In reversed shear plasmas, reversed-shear-induced AEs (RSAEs) and their transition to TAEs as the minimum value of the safety factor decreases has been observed. Neutron measurements suggest energetic ion loss is large in the transition phase from RSAEs to TAEs.

Journal Articles

Energetic neutral particle measurement with natural diamond detector in JT-60U

Kusama, Yoshinori; Ishikawa, Masao; Takechi, Manabu; Nishitani, Takeo; Morioka, Atsuhiko; Sasao, Mamiko*; Isobe, Mitsutaka*; Krasilnikov, A.*; Kaschuck, Y.*

Proceedings of Plasma Science Symposium 2005/22nd Symposium on Plasma Processing (PSS-2005/SPP-22), p.395 - 396, 2005/00

The energetic neutral particles have been successfully measured with a natural diamond detector in the neutron and $$gamma$$ ray radiation circumstance of the JT-60U deuterium discharges. The diamond detector was covered with polyethylene and lead in order to reduce the neutron and $$gamma$$ ray background. The shield has shown expected shielding capability. A rapid increase in neutral particles has been observed at the onset of the Toroidal Alfven Eigenmode (TAE) excited by the negative-ion-based neutral beam injection. The energy range of increased neutral particles has agreed well with that predicted from the resonant interaction between the energetic ions and the TAE.

Journal Articles

Escaping fast ion diagnostics for the fast particle transport analysis

Isobe, Mitsutaka*; Shinohara, Koji

Purazuma, Kaku Yugo Gakkai-Shi, 80(12), p.1036 - 1043, 2004/12

Escaping energetic ion diagnostics in magnetically confined plasma experiments are described in this lecture note. Experimental results from escaping energetic ion diagnostics in TFTR, JFT-2M, CHS and W7-AS are shown. In addition to mechanism of energetic ion loss from a viewpoint of particle orbit, effect of MHD activity on energetic particle transport is reviewed.

Journal Articles

Charge exchange neutral particle measurements with natural diamond detector under the deuterium-deuterium neutron field on JT-60U tokamak

Ishikawa, Masao; Kusama, Yoshinori; Takechi, Manabu; Nishitani, Takeo; Morioka, Atsuhiko; Sasao, Mamiko*; Isobe, Mitsutaka*; Krasilnikov, A.*; Kaschuck, Y. A.*

Review of Scientific Instruments, 75(10), p.3643 - 3645, 2004/10

 Times Cited Count:5 Percentile:33.07(Instruments & Instrumentation)

Measurement of energy distribution of charge exchange neutral particles by using Natural Diamond Detector (NDD) has been started on the JT-60U Tokamak. Because the NDD is sensitive to neutrons and $$gamma$$-rays too, the radiation shield has been set up around the NDD. Then energy distribution of neutral particles corresponding to injected neutral beam energy are successfully obtained. Also, enhance of neutral particle flux due to sawtooth oscillation and Alfven Eigenmode induced by N-NBI was observed. The performance of the NDD as CX neutral particle analyzer under the DD neutron filed was demonstrated on JT-60U.

Journal Articles

Achievement of high fusion triple product, steady-state sustainment and real-time NTM stabilization in high-$$beta_p$$ ELMy H-mode discharges in JT-60U

Isayama, Akihiko; Kamada, Yutaka; Hayashi, Nobuhiko; Suzuki, Takahiro; Oikawa, Toshihiro; Fujita, Takaaki; Fukuda, Takeshi; Ide, Shunsuke; Takenaga, Hidenobu; Ushigusa, Kenkichi; et al.

Nuclear Fusion, 43(10), p.1272 - 1278, 2003/10

 Times Cited Count:126 Percentile:96.3(Physics, Fluids & Plasmas)

no abstracts in English

Journal Articles

A Report on the 12th topical conference on high temperature plasma diagnostics

Kodama, Ryosuke*; Yoshida, Hidetoshi; *; Nishitani, Takeo; Muto, Sadatsugu*; *; Matsuda, Toshiaki; *; Kawahata, Kazuo*; Isobe, Mitsutaka*; et al.

Purazuma, Kaku Yugo Gakkai-Shi, 74(10), p.1208 - 1213, 1998/10

no abstracts in English

Journal Articles

Transport and loss of energetic ions in JT-60U

Tobita, Kenji; Nishitani, Takeo; Harano, Hideki*; Tani, Keiji; Isobe, Mitsutaka*; Fujita, Takaaki; Kusama, Yoshinori; G.A.Wurden*; Shirai, Hiroshi; Oikawa, Toshihiro; et al.

Fusion Energy 1996, Vol.1, p.497 - 505, 1997/00

no abstracts in English

37 (Records 1-20 displayed on this page)