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Journal Articles

Neutronic analysis for ${it in situ}$ calibration of ITER in-vessel neutron flux monitor with microfission chamber

Ishikawa, Masao; Kondoh, Takashi; Kusama, Yoshinori; Bertalot, L.*

Fusion Engineering and Design, 88(6-8), p.1377 - 1381, 2013/10

 Times Cited Count:0 Percentile:0.01(Nuclear Science & Technology)

Neutronic analysis is performed for ${it in situ}$ calibration of the in-vessel neutron flux monitor in ITER, the Microfission Chamber (MFC). The transfer system of a neutron generator, which consists of two toroidal rings and a neutron generator holder, has been designed and its effect on the detection efficiency of the MFC is estimated through neutronic analysis with MCNP. The result indicates that the designed transfer system is unaffected for the detection efficiency of the MFC. ${it In situ}$ calibrations for the point by point method and the rotation method are simulated and compared through neutronic analysis. It is found that the rotation method is appropriate for full calibration because this method has the advantage that the calibration time can be shortened and all neutron flux monitors can be calibrated simultaneously.

Journal Articles

Neutronic analysis of the ITER poloidal polarimeter

Ishikawa, Masao; Kawano, Yasunori; Imazawa, Ryota; Sato, Satoshi; Vayakis, G.*; Bertalot, L.*; Yatsuka, Eiichi; Hatae, Takaki; Kondoh, Takashi; Kusama, Yoshinori

Fusion Engineering and Design, 86(6-8), p.1286 - 1289, 2011/10

 Times Cited Count:0 Percentile:0.01(Nuclear Science & Technology)

The nuclear heating rates of the optical mirrors of the poloidal polarimeter installed in the equatorial port plug of ITER are calculated. Since the system cannot have a sufficiently labyrinthine structure and the second mirrors are located nearly as close to the plasma as the first mirrors due to limited space, the nuclear heating rate of the second mirrors is as high as that of the first mirrors. However, it is possible to reduce the nuclear heating rates of the mirrors if the blanket shield module provides a sufficient degree of neutron shielding.

Journal Articles

Nuclear technology aspects of ITER vessel-mounted diagnostics

Vayakis, G.*; Bertalot, L.*; Encheva, A.*; Walker, C.*; Brichard, B.*; Cheon, M. S.*; Chitarin, G.*; Hodgson, E.*; Ingesson, C.*; Ishikawa, Masao; et al.

Journal of Nuclear Materials, 417(1-3), p.780 - 786, 2011/10

 Times Cited Count:19 Percentile:83.81(Materials Science, Multidisciplinary)

Journal Articles

Effect of thermal neutrons on fusion power measurement using the microfission chamber in ITER

Ishikawa, Masao; Kondoh, Takashi; Nishitani, Takeo; Kusama, Yoshinori

Fusion Engineering and Design, 86(4-5), p.417 - 420, 2011/06

 Times Cited Count:0 Percentile:0.01(Nuclear Science & Technology)

A Microfission Chamber (MFC) provides time-resolved measurements of global neutron source strength in ITER. Measurements of the neutron source strength could be affected by cooling water in branch pipes installed near the MFC. The effect of the branch pipes upon the MFC is assessed through neutron transport calculation. Results indicate a significant increase in the MFC response rate due to the branch pipe. The increase in the MFC response is caused by the slowing down of the neutrons due to the cooling water in the branch pipes. One possible solution to reduce the effect is to cover the MFC with a material that absorbs thermal neutrons such as cadmium. The ways in which the absorbent material may affect MFC response is analyzed through neutron transport calculation. Results indicate that the increase in the MFC response can be reduced to $$<$$ 10% through cadmium coating.

Journal Articles

Development of in-vessel components of the microfission chamber for ITER

Ishikawa, Masao; Kondoh, Takashi; Okawa, Kiyofumi*; Fujita, Kyoichi*; Yamauchi, Michinori*; Hayakawa, Atsuro*; Nishitani, Takeo; Kusama, Yoshinori

Review of Scientific Instruments, 81(10), p.10D308_1 - 10D308_3, 2010/10

 Times Cited Count:2 Percentile:14.37(Instruments & Instrumentation)

Microfission chambers (MFCs) will provide total neutron source strength in ITER. The MFC is a pencil-sized gas counter containing the fissile material, $$^{235}$$U. The MFCs will be installed behind blanket modules in the vacuum vessel (VV). Double coaxial mineral insulated (MI) cables will carry signals from the MFCs to the upper port. Though the MI cables will be installed at a factory of the vacuum vessel or ITER assembly hall, detectors with $$^{235}$$U will be installed to the vacuum vessel at the tokamak pit. Then, the MI cable should be connected in the vacuum vessel. In this work, the connection of the MI cable with the MFC was conceptually designed. The MI cable should be also installed with small curvature radius (R) of 100 $$sim$$ 200 mm to avoid the VV structure and other diagnostics. So, the vending test of the MI cable was conducted. As a result, damages leak, electrical disconnection and the change in insulation resistance have not been observed at R = 100 mm.

Journal Articles

Neutron transport analysis for in-vessel diagnostics in ITER

Ishikawa, Masao; Kondoh, Takashi; Nishitani, Takeo; Kawano, Yasunori; Kusama, Yoshinori

Journal of Plasma and Fusion Research SERIES, Vol.9, p.43 - 47, 2010/08

Neutron transport analysis is very important for design and optimization of diagnostics in ITER. Especially, in-vessel diagnostics are exposed to strong neutron and $$gamma$$ radiation and then it could lead to damage and temperature increase due to nuclear heating of the components of those diagnostics. High dose rate due to strong radiation also makes those maintenances difficult. Therefore, evaluation of neutron/$$gamma$$ flux, spectrum and nuclear heating at the location of the diagnostics with neutron transport analysis are essential to design a neutron radiation shield system and/or a cooling system. In this paper, results of neutron transport analysis applied to in-vessel components of the microfission chamber (MFC) and the poloidal polarimeter, which are developed by Japan Atomic Energy Agency, are presented.

Journal Articles

Development of the microfission chamber for fusion power diagnostics on ITER

Ishikawa, Masao; Kondoh, Takashi; Nishitani, Takeo; Kusama, Yoshinori

Journal of Plasma and Fusion Research SERIES, Vol.8, p.334 - 337, 2009/09

Microfission chambers (MFCs) are one of the most important diagnostics to measure total neutron source strength in ITER. The MFCs will be installed behind blanket modules upper outboard and lower outboard in the vacuum vessel. Double coaxial mineral insulated (MI) cables as signal cables are also installed form the MFCs to the upper port. It is very difficult to install the MI cables together with the MFC because of the security regulation. In this design work, a new type of MFC, which can be separable from the MI cable, has been designed. On the other hand, steaming neutrons along the gap between two blanket modules can affect the absolute measurement of total neutron source strength. The effects of streaming neutrons tat the installation position are investigated by a neutron Monte Carlo calculation using MCNP version 5 code. The result suggests that the effect of streaming neutrons should be taken into account if the MFCs are installed at the distance less than 20 cm from the gap.

Journal Articles

Engineering and maintenance studies of the ITER diagnostic upper port plug

Sato, Kazuyoshi; Omori, Junji; Kondoh, Takashi; Hatae, Takaki; Kajita, Shin*; Ishikawa, Masao; Neyatani, Yuzuru; Ebisawa, Katsuyuki*; Kusama, Yoshinori

Fusion Engineering and Design, 84(7-11), p.1713 - 1715, 2009/06

 Times Cited Count:1 Percentile:10.95(Nuclear Science & Technology)

Engineering analyses have been performed for the representative diagnostic upper port plug of ITER. Maintenance and integration design have been also carried out for the diagnostic components to be installed in the upper port plug. From the electromagnetic and structural analyses, it has come up an important problem to suppress the displacement of the upper port plug rather than to reduce the produced stress. Reducing the EM force will help to decrease the severity of potential displacement. Maximum displacement of the port plug decreases with increasing in the number of slits in a manner that the displacement would seem to be less than the design tolerance. A proposed low body roller and inner frame may enhance maintenance and integration. These studies and designs have established the design basis for the diagnostic upper port plug.

Journal Articles

Design of microfission chamber for ITER operations

Ishikawa, Masao; Kondoh, Takashi; Nishitani, Takeo; Kusama, Yoshinori

Review of Scientific Instruments, 79(10), p.10E507_1 - 10E507_4, 2008/10

 Times Cited Count:13 Percentile:54.32(Instruments & Instrumentation)

Micro-fission chambers (MFCs) are one of the most important diagnostics to measure the fusion power in ITER. The MFCs for high power operation (measurement range: fusion power of 100 kW - 1 GW) and MFCs for low power operation (fusion power of $$<$$ 100 kW) will be used in combination in order to cover the target measurement requirements of ITER. The MFCs for high power operation will be installed in the vacuum vessel. However, since size of the MFCs for low power operation is large, those will be installed in the equatorial (EQ) port. Several kinds of neutron shield exist between the plasma and MFCs. Then, we estimate the effect of these shields by a neutron Monte Carlo calculation using MCNP code. Effect of the changes in the plasma positions is also investigated. It is found that correction based on the position of the plasma center for output of the MFCs is needed for the horizontal changes in the plasma position for the MFC for low power operation.

Journal Articles

Absolute neutron emission measurement in burning plasma experiments

Nishitani, Takeo; Ishikawa, Masao; Kondoh, Takashi; Kusama, Yoshinori; Asai, Keisuke*; Sasao, Mamiko*

AIP Conference Proceedings 988, p.267 - 274, 2008/04

no abstracts in English

JAEA Reports

Detail design of microfission chamber for fusion power diagnostic on ITER

Ishikawa, Masao; Kondoh, Takashi; Hayakawa, Atsuro*; Nishitani, Takeo; Kusama, Yoshinori

JAEA-Technology 2007-062, 57 Pages, 2007/12

JAEA-Technology-2007-062.pdf:45.95MB

The microfission chambers (MFC)provide time-resolved measurements of the global neutron source strength and fusion power from ITER. In the previous work, it was found that combination of the MFC for low power operation and for high power operation can cover the target measurement requirement of ITER. Signals from the MFC are transferred by double coaxial mineral cable (MI) cable. These MFC will be installed in the vacuum vessel, so that the MI cables should be placed in the vacuum vessel. In this design work, the placing route of the MI cables from the installation position of the microfission chamber to the feed-through in the upper port is designed. As far placing of the MI cable, since the MI cable is filled with Ar gas at 14.6 atom, the double pipe structure that the outer pipe covers the MI cable is adopted in order to prevent the gas leak into the vacuum vessel. The exhaust system of the double pipe is also designed for detection and exhaust of the leaked Ar gas.

Journal Articles

Development of collective Thomson scattering for alpha-particle diagnostic in burning plasmas

Kondoh, Takashi; Hayashi, Toshimitsu; Kawano, Yasunori; Kusama, Yoshinori; Sugie, Tatsuo

Plasma and Fusion Research (Internet), 2, p.S1111_1 - S1111_4, 2007/11

A diagnostic of fusion-generated alpha-particles is important to understand burning plasma physics, however, an effective measurement method has not yet been established. A collective Thomson scattering (CTS) diagnostic CO$$_{2}$$ laser is being developed to establish a diagnostic method of confined alpha-particles. To realize the CTS diagnostic, a high-repetition Transversely Excited Atmospheric (TEA) CO$$_{2}$$ has been developed. In order to obtain single-mode output, which is needed for the CTS diagnostic, seed laser is injected to the cavity with an unstable resonator. Using this technique, output energy of 17J with the frequency of 15 Hz has been achieved with single-mode output. These results gives a prospect for the CTS diagnostic on International Thermonuclear Experimental Reactor (ITER), which requires energy of 20 J with the repetition rate of 40 Hz. Proof-of-principle test is being performed with the improved laser system on the JT-60U tokamak.

Journal Articles

Engineering design of the ITER invessel neutron monitor using micro-fission chambers

Nishitani, Takeo; Yamauchi, Michinori; Izumi, Mikio*; Hayakawa, Atsuro*; Ebisawa, Katsuyuki*; Kondoh, Takashi; Kusama, Yoshinori

Fusion Engineering and Design, 82(5-14), p.1192 - 1197, 2007/10

 Times Cited Count:4 Percentile:33.11(Nuclear Science & Technology)

no abstracts in English

Journal Articles

Progress in development of collective Thomson scattering diagnostic with high power CO$$_{2}$$ laser

Kondoh, Takashi; Kawano, Yasunori; Hatae, Takaki; Sugie, Tatsuo; Hayashi, Toshimitsu; Kusama, Yoshinori

NIFS-PROC-68, p.126 - 129, 2007/09

High power and high repetition CO$$_{2}$$ laser has been developed for collective Thomson scattering (CTS) diagnostic to establish a diagnostic method of confined $$alpha$$-particles in burning plasmas. Pulse energy of 17 J at a repetition rate of 15 Hz has been achieved in a single-mode operation. This result gives a prospect for the CTS diagnostic on International Thermonuclear Experimental Reactor (ITER), which requires energy of 20 J with repetition rate of 40 Hz. The laser injection test into the vacuum vessel of the JT-60U tokamak has been carried out to check the electric noise and stray signals of the receiver system using the new CO$$_{2}$$ laser without plasma. As a result, electrical noise has been decreased, however, stray signal due to multimode oscillation has been observed in about 30% of the pulses and a further improvement of the laser is needed.

Journal Articles

Progress in the ITER physics basis, 7; Diagnostics

Donn$'e$, A. J. H.*; Costley, A. E.*; Barnsley, R.*; Bindslev, H.*; Boivin, R.*; Conway, G.*; Fisher, R.*; Giannella, R.*; Hartfuss, H.*; von Hellermann, M. G.*; et al.

Nuclear Fusion, 47(6), p.S337 - S384, 2007/06

 Times Cited Count:291 Percentile:80.7(Physics, Fluids & Plasmas)

no abstracts in English

Journal Articles

CO$$_{2}$$ laser collective Thomson scattering diagnostic of $$alpha$$-particles in burning plasmas

Kondoh, Takashi; Hayashi, Toshimitsu; Kawano, Yasunori; Kusama, Yoshinori; Sugie, Tatsuo; Hirata, Mafumi*; Miura, Yukitoshi

Fusion Science and Technology, 51(2T), p.62 - 64, 2007/02

 Times Cited Count:3 Percentile:26.87(Nuclear Science & Technology)

A diagnostic of fusion-generated $$alpha$$-particles is important for the understanding of their contribution to plasma heating and plasma instabilities in burning plasmas. However, an effective measurement method has not yet been established. In International Thermonuclear Experimental Reactor (ITER), measurement of velocity and spatial distributions of confined $$alpha$$-particles requires temporal resolution of 0.1 s and spatial resolution of a/10, where a is the plasma minor radius of ITER. A collective Thomson scattering (CTS) diagnostic for the measurement of $$alpha$$ particles is being developed using carbon dioxide (CO$$_{2}$$) lasers. The CTS based on the CO$$_{2}$$ laser (wavelength 10.6 $$mu$$m) has an advantage of small plasma refraction, simplifying the tracking of the scattered radiation. To realize the CTS diagnostic, a high-repetition Transversely Excited Atmospheric (TEA) CO$$_{2}$$ laser is being developed. The laser was designed based on a commercially available laser, TEA CO$$_{2}$$ marking laser. Maximum output energy of 36 J has been obtained with a cavity configuration of stable resonator. In order to obtain single-mode output, which is needed for CTS diagnostic, seed laser is injected to the cavity with unstable resonator. Using this technique, output energy of 10 J at a frequency of 10 Hz has been achieved with single-mode output. Proof-of-principle test will be performed with the improved laser system on the JT-60U tokamak. In this paper, we will describe development of the new TEA laser system, measurement results of the CTS on the JT-60U tokamak. Application of the CTS diagnostic to the mirror systems will be also described.

Journal Articles

Advanced diagnostics for burning plasma experiments

Sasao, Mamiko*; Yamada, Hiroshi*; Baba, Mamoru*; Kondoh, Takashi; Peterson, B. J.*; Kawahata, Kazuo*; Mase, Atsushi*; Yoshikawa, Masayuki*; Azechi, Hiroshi*; Toi, Kazuo*; et al.

Fusion Science and Technology, 51(2T), p.40 - 45, 2007/02

 Times Cited Count:0 Percentile:0.01(Nuclear Science & Technology)

Several unexplored physics issues will be studied in burning plasma experiments, planned on ITER in the near future. To carry out these studies, it is essential to develop novel diagnostic systems, such as fusion product measurement systems and high-resolution, high-reliability profile measurement of various plasma parameters. Scientific research on "Advanced Diagnostics for Burning Plasma Experiment" was assigned as a priority area by MEXT in 2004, and more than 20 studies are currently underway under this program. The feasibility of several new diagnostic concepts applicable to ITER is examined and diagnostic components for these systems are now under development.

Journal Articles

Development of pulsed CO$$_2$$ laser for alpha-particle diagnostic

Kondoh, Takashi; Hayashi, Toshimitsu; Kawano, Yasunori; Kusama, Yoshinori; Sugie, Tatsuo

Tokutei Ryoiki Purazuma Nensho No Tameno Senshin Keisoku News Letter, (5), P. 2, 2006/11

no abstracts in English

Journal Articles

High-repetition CO$$_{2}$$ laser for collective Thomson scattering diagnostic of $$alpha$$ particles in burning plasmas

Kondoh, Takashi; Hayashi, Toshimitsu; Kawano, Yasunori; Kusama, Yoshinori; Sugie, Tatsuo; Miura, Yukitoshi; Koseki, Ryoji*; Kawahara, Yoshihiro*

Review of Scientific Instruments, 77(10), p.10E505_1 - 10E505_3, 2006/10

 Times Cited Count:6 Percentile:35.58(Instruments & Instrumentation)

A collective Thomson scattering (CTS) technique based on a pulsed CO$$_{2}$$ laser is being developed in order to establish a diagnostic method of confined $$alpha$$-particles in burning plasmas. In International Thermonuclear Experimental Reactor (ITER), measurement of velocity and spatial distributions of confined $$alpha$$-particles requires temporal resolution of 0.1 s and spatial resolution of a/10, where a is plasma minor radius. A new laser system (Energy $$>$$10J, repetition 10Hz) has been developed based on a commercially available laser (Shibuya Kogyo Co., Ltd, SEL4000) to meet the requirement of temporal resolution of ITER and to improve a signal-to-noise ratio. The laser has unstable resonator with a cavity length of 4 m and discharge electrodes with heat exchanger of laser gas for high-repetition operation. Proof-of-principle test of the CTS technique will be performed with the new laser system on JT-60U (JAEA Tokamak 60 - Upgrade). This work was supported by Grant-in-Aid for Scientific Research on Priority Areas "Advanced Diagnostics for Burning Plasmas" from Ministry of Education, Culture, Sports, Science and Technology, No.16082210.

Journal Articles

Simultaneous measurements of ion and electron currents using a novel compact electrostatic end-loss-current detector

Hirata, Mafumi*; Miyake, Yasuhiro*; Chujo, T.*; Kohagura, Junko*; Numakura, Tomoharu*; Shimizu, Kiyoaki*; Ito, Marie*; Kiminami, Serina*; Morimoto, Naomichi*; Hirai, Katsuaki*; et al.

Review of Scientific Instruments, 77(10), p.10E719_1 - 10E719_3, 2006/10

 Times Cited Count:0 Percentile:0.01(Instruments & Instrumentation)

no abstracts in English

143 (Records 1-20 displayed on this page)