Refine your search:     
Report No.
 - 
Search Results: Records 1-20 displayed on this page of 53

Presentation/Publication Type

Initialising ...

Refine

Journal/Book Title

Initialising ...

Meeting title

Initialising ...

First Author

Initialising ...

Keyword

Initialising ...

Language

Initialising ...

Publication Year

Initialising ...

Held year of conference

Initialising ...

Save select records

Journal Articles

Development of 300$$^{circ}$$C heat resistant boron-loaded resin for neutron shielding

Morioka, Atsuhiko; Sakurai, Shinji; Okuno, Koichi*; Sato, Satoshi; Verzirov, Y. M.; Kaminaga, Atsushi; Nishitani, Takeo; Tamai, Hiroshi; Shibama, Yusuke; Yoshida, Shigeru*; et al.

Journal of Nuclear Materials, 367-370(2), p.1085 - 1089, 2007/08

 Times Cited Count:20 Percentile:17.82(Materials Science, Multidisciplinary)

A 300$$^{circ}$$C heat-resistant neutron shielding material is newly developed, which consists of phenol-based resin with 6 weight-% boron. The neutron shielding performance of the developed resin, examined by the $$^{252}$$Cf neutron source, is almost the same as that of the polyethylene. The neutron shielding characteristic was also estimated by 3D Monte Carlo Code MCNP-4C2 using the continuous energy cross section data sets based on the JENDL-3.2. The calculation result agrees well with the experimental result. To understand the kinds of the outgas from the developed resin in the high temperature region, the mass spectrum of the outgas was measured until $$sim$$300$$^{circ}$$C by Thermal Desorption Specroscopy (TDS). The observed mass number was 2, 17, 18, 28, 32, and 44. The number corresponds to hydrogen (H$$_{2}$$), ammonia (NH$$_{3}$$), water (H$$_{2}$$O), carbon monoxide (CO), oxygen (O$$_{2}$$), carbon dioxide (CO$$_{2}$$), respectively. The main outgas component from the resin at 100$$sim$$150$$^{circ}$$C was NH $$_{3}$$ and H$$_{2}$$O. The outgas of NH$$_{3}$$ and H$$_{2}$$O from the resin have been measured, however, the neutron shielding performance of the resin after 200$$^{circ}$$C baking was almost the same as that before baking. The quantitative analysis of the outgas from the resin in the high temperature region was done by the Temperature Programmed Desorption (TPD) / Gas Chromatography and Mass spectrometry (GC/MS). The 13 kinds of organic gases have been observed by the amount of $$mu$$g/g at 300$$^{circ}$$C. The neutron shielding performance of the developed resin at 300$$^{circ}$$C was simulated by the 3D analysis. The resonance cross section of the nucleus is broad at the high temperature region by the Doppler effect. The calculation results using 327$$^{circ}$$C library and 20$$^{circ}$$C library are almost same.

Journal Articles

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

Ishikawa, Masao; Takechi, Manabu; Shinohara, Koji; Cheng, C. Z.*; Matsunaga, Go; Kusama, Yoshinori; Fukuyama, Atsushi*; Nishitani, Takeo; Morioka, Atsuhiko; Sasao, Mamiko*; et al.

Nuclear Fusion, 47(8), p.849 - 855, 2007/08

 Times Cited Count:18 Percentile:41.11(Physics, Fluids & Plasmas)

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 and then saturate as the minimum value of the safety factor decrease, have been observed in JT-60U. These mode behavior can be explained by RSAEs and the transition from RSAEs to TAEs. Measured total neutron emission rate in the presence of these 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.

Journal Articles

Overview of national centralized tokamak program; Mission, design and strategy to contribute ITER and DEMO

Ninomiya, Hiromasa; Akiba, Masato; Fujii, Tsuneyuki; Fujita, Takaaki; Fujiwara, Masami*; Hamamatsu, Kiyotaka; Hayashi, Nobuhiko; Hosogane, Nobuyuki; Ikeda, Yoshitaka; Inoue, Nobuyuki; et al.

Journal of the Korean Physical Society, 49, p.S428 - S432, 2006/12

To contribute DEMO and ITER, the design to modify the present JT-60U into superconducting coil machine, named National Centralized Tokamak (NCT), is being progressed under nationwide collaborations in Japan. Mission, design and strategy of this NCT program is summarized.

Journal Articles

Poloidal field coil configuration and plasma shaping capability in NCT

Matsukawa, Makoto; Tamai, Hiroshi; Fujita, Takaaki; Kizu, Kaname; Sakurai, Shinji; Tsuchiya, Katsuhiko; Kurita, Genichi; Morioka, Atsuhiko; Ando, Toshinari; Miura, Yushi

IEEE Transactions on Applied Superconductivity, 16(2), p.914 - 917, 2006/06

 Times Cited Count:4 Percentile:69.01(Engineering, Electrical & Electronic)

no abstracts in English

Journal Articles

Overview of the national centralized tokamak programme

Kikuchi, Mitsuru; Tamai, Hiroshi; Matsukawa, Makoto; Fujita, Takaaki; Takase, Yuichi*; Sakurai, Shinji; Kizu, Kaname; Tsuchiya, Katsuhiko; Kurita, Genichi; Morioka, Atsuhiko; et al.

Nuclear Fusion, 46(3), p.S29 - S38, 2006/03

 Times Cited Count:13 Percentile:54.2(Physics, Fluids & Plasmas)

The National Centralized Tokamak (NCT) facility program is a domestic research program for advanced tokamak research to succeed JT-60U incorporating Japanese university accomplishments. The mission of NCT is to establish high beta steady-state operation for DEMO and to contribute to ITER. The machine flexibility and mobility is pursued in aspect ratio and shape controllability, feedback control of resistive wall modes, wide current and pressure profile control capability for the demonstration of the high-b steady state.

Journal Articles

Engineering design and control scenario for steady-state high-beta operation in national centralized tokamak

Tsuchiya, Katsuhiko; Akiba, Masato; Azechi, Hiroshi*; Fujii, Tsuneyuki; Fujita, Takaaki; Fujiwara, Masami*; Hamamatsu, Kiyotaka; Hashizume, Hidetoshi*; Hayashi, Nobuhiko; Horiike, Hiroshi*; et al.

Fusion Engineering and Design, 81(8-14), p.1599 - 1605, 2006/02

 Times Cited Count:1 Percentile:89.15(Nuclear Science & Technology)

no abstracts in English

Journal Articles

Nuclear technology and potential ripple effect of superconducting magnets for fusion power plant

Nishimura, Arata*; Muroga, Takeo*; Takeuchi, Takao*; Nishitani, Takeo; Morioka, Atsuhiko

Fusion Engineering and Design, 81(8-14), p.1675 - 1681, 2006/02

 Times Cited Count:3 Percentile:73.3(Nuclear Science & Technology)

In a fusion reactor plant, a neutral beam injector (NBI) will be operated for a long time, and it will allow neutron streaming from NBI ports to outside of the plasma vacuum vessel. It requires the superconducting magnet to develop nuclear technology to produce stable magnetic field and to reduce activation of the magnet components. In this report, the back ground of the necessity and the contents of the nuclear technology of the superconducting magnets for fusion application are discussed and some typical investigation results are presented, which are the neutron irradiation effect on Nb$$_{3}$$Sn wire, the development of low activation superconducting wire, and the design concept to reduce nuclear heating and nuclear transformation by streaming. In addition, recent activities in high energy particle physics are introduced and potential ripple effect of the technology of the superconducting magnets is described briefly.

Journal Articles

Development of high heat-resistance resin for neutron shielding

Morioka, Atsuhiko; Okuno, Koichi*

Purasuchikkusu, 57(1), p.148 - 152, 2006/01

no abstracts in English

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:35 Percentile:23.87(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

Design study of national centralized tokamak facility for the demonstration of steady state high-$$beta$$ plasma operation

Tamai, Hiroshi; Akiba, Masato; Azechi, Hiroshi*; Fujita, Takaaki; Hamamatsu, Kiyotaka; Hashizume, Hidetoshi*; Hayashi, Nobuhiko; Horiike, Hiroshi*; Hosogane, Nobuyuki; Ichimura, Makoto*; et al.

Nuclear Fusion, 45(12), p.1676 - 1683, 2005/12

 Times Cited Count:15 Percentile:50.65(Physics, Fluids & Plasmas)

Design studies are shown on the National Centralized Tokamak facility. The machine design is carried out to investigate the capability for the flexibility in aspect ratio and shape controllability for the demonstration of the high-beta steady state operation with nation-wide collaboration, in parallel with ITER towards DEMO. Two designs are proposed and assessed with respect to the physics requirements such as confinement, stability, current drive, divertor, and energetic particle confinement. The operation range in the aspect ratio and the plasma shape is widely enhanced in consistent with the sufficient divertor pumping. Evaluations of the plasma performance towards the determination of machine design are presented.

Journal Articles

Development of a heat-resistant neutron shielding resin for the national centralized tokamak

Morioka, Atsuhiko; Sakurai, Shinji; Okuno, Koichi*; Tamai, Hiroshi

Purazuma, Kaku Yugo Gakkai-Shi, 81(9), p.645 - 646, 2005/09

A 300 $$^{circ}$$C heat-resistant neutron shielding material is newly developed, which consists of phenol-based resin with 5 weight-% boron. The neutron shielding performance of the developed resin, examined by the $$^{252}$$Cf neutron source, is almost the same as that of the polyethylene. The resin is applicable to the port section of vacuum vessel of the DD plasma device to suppress the streaming neutrons and to reduce the nuclear heating of the superconducting coils.

Journal Articles

Alfv$'e$n eigenmodes in reversed shear plasmas in JT-60U negative-ion-based neutral beam injection discharges

Takechi, Manabu; Fukuyama, Atsushi*; Ishikawa, Masao; Cheng, C. Z.*; Shinohara, Koji; Ozeki, Takahisa; Kusama, Yoshinori; Takeji, Satoru*; Fujita, Takaaki; Oikawa, Toshihiro; et al.

Physics of Plasmas, 12(8), p.082509_1 - 082509_7, 2005/08

 Times Cited Count:28 Percentile:30.36(Physics, Fluids & Plasmas)

Rapid frequency sweeping modes observed in reversed magnetic shear (RS) plasmas on the Japan Atomic Energy Research Institute Tokamak 60 Upgrade (JT-60U) have been identified as Reversed-Shear-induced Alfv$'e$n Eigenmodes (RSAEs), which are ideal MHD Alfv$'e$n eigenmodes (AEs) localized to the region of minimum safety factor, $$q_{rm min}$$, and are excited by negative-ion-based neutral beam injection. The chirping and subsequent saturation of the mode frequency are consistent with theoretical predictions for the transition from RSAEs to Toroidal Alfv$'{e}$n eigenmodes (TAEs). The previously observed rapid frequency sweeping modes in ion cyclotron wave heated plasmas in JT-60U can also be similarly explained. The observed AE amplitude is largest during the transition from RSAEs to TAEs, and fast ion loss is observed when the AE amplitude is largest at this transition. It is preferable to operate outside the transition range of $$q$$$$_{min}$$, e.g., 2.4 $$<$$ $$q$$$$_{min}$$ $$<$$ 2.7 for the n = 1 AE to avoid substantial fast ion loss in RS plasmas.

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

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:66.22(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

Irradiation and penetration tests of boron-doped low activation concrete using 2.45 MeV and 14 MeV neutron sources

Morioka, Atsuhiko; Sato, Satoshi; Kinno, Masaharu*; Sakasai, Akira; Hori, Junichi*; Ochiai, Kentaro; Yamauchi, Michinori*; Nishitani, Takeo; Kaminaga, Atsushi; Masaki, Kei; et al.

Journal of Nuclear Materials, 329-333(2), p.1619 - 1623, 2004/08

 Times Cited Count:7 Percentile:52.07(Materials Science, Multidisciplinary)

The neutron penetration and the activation characteristics of the boron-doped low activation concrete were investigated for irradiation of 2.45 and 14 MeV neutrons. The shielding property of the 2 wt% boron-doped low activation concrete is superior to that of the 1 wt% boron for the thermal neutron, on the contrary to the no clear difference for the fast neutron. The total activity detected in the boron-doped low activation concrete was about one hundredth of that in the geostandard sample at more than 30 days cooling time. The total activity of the boron-doped concrete by major nuclei does not depend on the boron density for the 14 MeV neutron irradiation.

Journal Articles

Advanced control scenario of high-performance steady-state operation for JT-60 superconducting tokamak

Tamai, Hiroshi; Kurita, Genichi; Matsukawa, Makoto; Urata, Kazuhiro*; Sakurai, Shinji; Tsuchiya, Katsuhiko; Morioka, Atsuhiko; Miura, Yushi; Kizu, Kaname; Kamada, Yutaka; et al.

Plasma Science and Technology, 6(3), p.2281 - 2285, 2004/06

 Times Cited Count:0 Percentile:100(Physics, Fluids & Plasmas)

High performance steady-state operation for JT-60SC are evaluated by the TOPICS analysis. $$beta$$$$_N$$$$sim$$5 and bootstrap current fraction $$sim$$86% is kept steady at I$$_p$$=1.5 MA, B$$_t$$=2 T by neutral beam power of 11 MW. The ERATO-J analysis shows that the external-kink mode with multiple toroidal mode numbers of n=1 and n=2 is stable at $$beta$$$$_N$$ $$leq$$5.5 at the average ratio of conducting wall radius to plasma minor radius of about 1.2 with the wall stabilisation effect. Resistive wall modes, induced by a close location of the wall to plasma, is expected to be suppressed by the active feedback stabilisation with a set of non-axisymmetric field coils behind the stabilising plates. Further optimisation for the high-$$beta$$$$_N$$ accessibility by the plasma shaping is performed with the TOSCA analysis. The plasma shaping factor defined as S=(I$$_p$$/aB$$_t$$)q$$_9$$$$_5$$ and strongly correlated to the plasma elongation and triangularity, is scanned from $$sim$$4 to $$sim$$6, which extends the availability of current and pressure profile control for the high performance plasma operation.

Journal Articles

Experimental study on induced radioactivity in boron-doped low activation concrete for DT fusion reactors

Sato, Satoshi; Morioka, Atsuhiko; Kinno, Masaharu*; Ochiai, Kentaro; Hori, Junichi; Nishitani, Takeo

Journal of Nuclear Science and Technology, 41(Suppl.4), p.66 - 69, 2004/03

no abstracts in English

Journal Articles

Neutron transmission experiment of boron-doped resin for the JT-60SC neutron shield using 2.45 MeV neutron source

Morioka, Atsuhiko; Sato, Satoshi; Ochiai, Kentaro; Sakasai, Akira; Hori, Junichi; Yamauchi, Michinori*; Nishitani, Takeo; Kaminaga, Atsushi; Masaki, Kei; Sakurai, Shinji; et al.

Journal of Nuclear Science and Technology, 41(Suppl.4), p.109 - 112, 2004/03

Neutron shielding material of the port section of JT-60 superconducting modification (JT-60SC) serves as a design which used resin (KRAFTON-HB4) excellent in the temperature characteristic from polyethylene. In order to make port weight mitigate and reduce the nuclear heating of the superconducting coil, we were developed the resin which added natural BORON to resin. The 2.45MeV neutron generated in the D-D reaction was irradiated, the penetration of the neutron was measured in some kinds of samples which changed the amount of BORON, and the shielding performance of the resin containing BORON was compared with them. The penetration rates of fast neutron flux do not depend on the doped density of boron in both measurements. Whereas the penetration rates of thermal neutron flux in the resin with 2 wt% B are about 25% lower than those with 1 wt% at the back surface of the test specimens.

Journal Articles

Advanced fusion technologies developed for JT-60 superconducting Tokamak

Sakasai, Akira; Ishida, Shinichi; Matsukawa, Makoto; Akino, Noboru; Ando, Toshinari*; Arai, Takashi; Ezato, Koichiro; Hamada, Kazuya; Ichige, Hisashi; Isono, Takaaki; et al.

Nuclear Fusion, 44(2), p.329 - 334, 2004/02

no abstracts in English

Journal Articles

Advanced fusion technologies developed for JT-60 superconducting Tokamak

Sakasai, Akira; Ishida, Shinichi; Matsukawa, Makoto; Akino, Noboru; Ando, Toshinari*; Arai, Takashi; Ezato, Koichiro; Hamada, Kazuya; Ichige, Hisashi; Isono, Takaaki; et al.

Nuclear Fusion, 44(2), p.329 - 334, 2004/02

 Times Cited Count:7 Percentile:74.52(Physics, Fluids & Plasmas)

no abstracts in English

53 (Records 1-20 displayed on this page)