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259 results on '"Kisaki M."'

1. Development of a set of movable electrostatic probes to characterize the plasma in the ITER neutral beam negative-ion source prototype

Author

Sartori, E., Brombin, M., Laterza, B., Zuin, M., Cavazzana, R., Cervaro, V., Degli Agostini, F., Fadone, M., Fasolo, D., Grando, L., Jain, P., Kisaki, M., Maistrello, A, Moro, G, Pimazzoni, A., Poggi, C., Segalini, B., Shepherd, A., Spolaore, M., Taliercio, C., Tollin, M., Ugoletti, M., Veltri, P., Zamengo, A., and Serianni, G.

Published
2021
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8. Strategy for Vacuum Insulation Tests of MITICA 1 MV Electrostatic Accelerator

Author

Chitarin, G., primary, Kojima, A., additional, Boldrin, M., additional, Luchetta, A., additional, Marcuzzi, D., additional, Zaccaria, P., additional, Zanotto, L., additional, Toigo, V., additional, Aprile, D., additional, Marconato, N., additional, Patton, T., additional, Pilan, N., additional, Barbato, P., additional, Berton, G., additional, Breda, M., additional, Dan, M., additional, Fincato, M., additional, Lotto, L., additional, Rigoni-Garola, A., additional, Sartori, E., additional, Tollin, M., additional, Valente, M., additional, Grando, L., additional, Pomaro, N., additional, De Lorenzi, A., additional, Hiratsuka, J., additional, Ichikawa, M., additional, Kisaki, M., additional, Murayama, M., additional, Saquilayan, G. M., additional, Tobari, H., additional, Umeda, N., additional, Watanabe, K., additional, and Kashiwagi, M., additional

Published
2022
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9. Nonuniform plasma meniscus modelling based on backward calculation of negative ion beamlet

Author

Kisaki, M., Nagaoka, K., Slief, J.H., Haba, Y., Nakamoto, R., Tsumori, K., Nakano, H., Ikeda, K., Osakabe, M., Kisaki, M., Nagaoka, K., Slief, J.H., Haba, Y., Nakamoto, R., Tsumori, K., Nakano, H., Ikeda, K., and Osakabe, M.

Abstract

The shape of a plasma meniscus is a key factor to determine the beam focusing. The physics model of the meniscus formation for hydrogen negative ion sources has not been established yet. A backward trajectory calculation based on experimental observation is performed in order to derive the particle information at the meniscus. It is observed that the negative ion density is spatially nonuniform in the direction parallel to the magnets for suppression of co-extracted electrons. A nonuniformity of the negative ion density in the vicinity of the meniscus is taken into account in the forward trajectory calculation. It reveals that the nonuniform negative ion distribution leads to degradation of the beam focusing and the beam splitting in phase space. The importance of the spatial distribution of negative ions on meniscus modelling is discussed with a comparison to uniform extraction model.

Published
2022

18. The stress field caused by a circular cylindrical inclusion in a transversely isotropic elastic solid

Author

Hasegawa, H. and Kisaki, M.

Subjects
Mechanics -- Research, Science and technology
Abstract

Exact solutions are presented in closed form for the axisymmetric stress and displacement fields caused by a circular solid cylindrical inclusion with uniform eigenstrain in a transversely isotropic elastic solid. This is an extension of a previous paper for an isotropic elastic solid to a transversely isotropic solid. The strain energy is also shown. The method of Green's functions is used. The numerical results for stress distributions are compared with those for art isotropic elastic solid. [DOI: 10.1115/1.1629755]

Published
2003

20. NIBS2020 poster Q+A

Author

Bito, K., primary, Faircloth, D., additional, Gamba, D., additional, Heiler, A., additional, Hernandez, J., additional, Huh, S., additional, Kisaki, M., additional, Lawrie, S., additional, Li, Z., additional, Shi, C., additional, Shimabukuro, Y., additional, Wang, J., additional, Wang, N., additional, Wang, R., additional, and Xu, Y., additional

Published
2021
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25. NIBS2020 poster Q+A.

Author

Bito, K., Faircloth, D., Gamba, D., Heiler, A., Hernandez, J., Huh, S., Kisaki, M., Lawrie, S., Li, Z., Shi, C., Shimabukuro, Y., Wang, J., Wang, N., Wang, R., and Xu, Y.

Subjects
POSTER presentations, POSTERS, MANUSCRIPTS
Abstract

This manuscript groups together all the text based Questions and Answers (Q+A) from the poster presentations at NIBS2020. [ABSTRACT FROM AUTHOR]

Published
2021
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32. Caesiated H- source operation with helium

Author

Tsumori, K., primary, Wada, M., additional, Nakano, H., additional, Kisaki, M., additional, Ikeda, K., additional, Haba, Y., additional, Nagaoka, K., additional, Kamio, S., additional, Fujiwara, Y., additional, and Osakabe, M., additional

Published
2018
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35. First measurements of beam plasma in NIFS test stand

Author

Sartori, E., primary, Nakano, H., additional, Veltri, P., additional, Kisaki, M., additional, Pimazzoni, A., additional, Brombin, M., additional, Antoni, V., additional, Cervaro, V., additional, Ikeda, K., additional, Tsumori, K., additional, and Serianni, G., additional

Published
2018
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37. Synergy of numerical simulations and experimental measurements to improve the interpretation of negative ion beam properties

Author

Serianni G., Agostinetti P., Antoni V., Aprile D., Brombin M., Cavenago M., Chitarin G., Delogu R., Marconato N., Pasqualotto R., Pimazzoni A., Sartori E., Veltri P., Kaneko O., Takeiri Y., Osakabe M., Nagaoka K., Ikeda K., Nakano H., Kisaki M., and Tsumori K.

Abstract

The ITER tokamak requires two heating Neutral Beam Injectors (NBIs), based on the neutralisation of 40A of negative hydrogen/deuterium ions accelerated to 1MeV with a pulse length of one hour. As these simultaneous parameters were never experimentally achieved, in order to optimise source operation and to assess beam properties, a specific test facility ("PRIMA") was established in Padova, comprising two experiments: SPIDER (full-size negative ion source with 40A beam, 100keV particle energy) and MITICA, the prototype of ITER NBIs. A key NBI component is the particle accelerator, where electrostatic and magnetic fields produce the beam optics. The design of SPIDER and MITICA accelerators was based on the most advanced numerical codes available for the investigation of the expected beam properties and on the most up-to-date experience of various research groups. Several diagnostic systems will characterise source and beam during the experiments. In view of the operation, effort is presently devoted (within bilateral collaboration frameworks between Italian and Japanese agencies) to the preparation for the synergistic employment of simulations and experiments. Specifically, a characterisation of the beam properties is carried out in the NIFS-R&D multi-cusp negative ion source (NIFS-RNIS) by a sophisticated set of source and beam diagnostic systems. Simulations are mainly performed at Consorzio RFX, by a suite of numerical tools to compute or investigate various aspects of beam physics. Preliminary comparisons showed very good agreement between simulations and measured data regarding the basic features of the accelerator. The present contribution describes the synergy between numerical codes and diagnostic techniques. Both are applied to real-time characterisation of the beam, with the main scopes of providing interpretation of the measured results and of supplying data for successive choices during the operation. These activities allow also extensive validation of numerical models and the choice of the most useful set of codes to be used in future experiments like DEMO.

Published
2016

38. Progress of Experimental Study on Negative Hydrogen Ion Production and Extraction

Author

Kisaki M., Tsumori K., Ikeda K., Nakano H., Geng S., Tokuzawa T., Osakabe M., Nagaoka K., Agostinetti P., Brombin M., Hatayama A., Nishioka S., Sartori E., Serianni G., Veltri P., Kaneko O., and Takeiri Y.

Abstract

Development of the high performance negative hydrogen ion source is a fundamental demand in realizing fusion reactor. In order to clarify the extraction mechanism of H´, temporal and spatial variations of the negative ions and electrons in the extraction region are intensively surveyed at NIFS. In addition, the beam acceleration experiments have been performed by changing the accelerator configuration in order to improve the voltage holding capability and to study the negative ion beam optics. In a caesiated hydrogen plasma, it was observed that the negative hydrogen ion density (nH´) becomes one order higher in magnitude than the electron density (n e) in the vicinity of the plasma grid (PG). The response of negative-ion rich plasmas to the extraction field was investigated by measuring the plasma potential (V p) profiles in the axis perpendicular to the PG before and during beam extraction. The V p increases with applying the extraction field, and the influence of the extraction field on the V p was observed at 30 mm from the PG. As for the nH´, it was also observed that the extraction field affects on the nH´ at 30 mm from the PG, where the nH´ decreases simultaneously with the beam extraction. These observations indicate that the extraction field affects the particle dynamics in the wide region extending over 30 mm from the PG. This feature is completely different from that of electron-ion plasmas. We also found that the negative ion production efficiency becomes twice higher by changing the shape of grounded grid holes without any modification on the plasma chamber. We assumed that the behaviour of the back-streaming ion was affected by changing the GG. The back-streaming ion trajectory was analyzed with the beam trajectory simulation, and it was found that the back-streaming ion distributes in the larger area on the back plate with the slot GG. This implies that some part of condensed Cs on the back plate was more effectively evaporated by the back-streaming ion with the slot GG and that Cs flux onto the PG surface increased, which resulted in the enhancement of the negative ion production. This result suggests that the accelerator configuration is one of the key factors to determine the negative ion production efficiency and that the Cs consumption can be reduced by the Cs recycling from the wall of the ion source chamber.

Published
2016

39. Extension of the operational regime of the LHD towards a deuterium experiment

Author

Takeiri, Y., primary, Morisaki, T., additional, Osakabe, M., additional, Yokoyama, M., additional, Sakakibara, S., additional, Takahashi, H., additional, Nakamura, Y., additional, Oishi, T., additional, Motojima, G., additional, Murakami, S., additional, Ito, K., additional, Ejiri, A., additional, Imagawa, S., additional, Inagaki, S., additional, Isobe, M., additional, Kubo, S., additional, Masamune, S., additional, Mito, T., additional, Murakami, I., additional, Nagaoka, K., additional, Nagasaki, K., additional, Nishimura, K., additional, Sakamoto, M., additional, Sakamoto, R., additional, Shimozuma, T., additional, Shinohara, K., additional, Sugama, H., additional, Watanabe, K.Y., additional, Ahn, J.W., additional, Akata, N., additional, Akiyama, T., additional, Ashikawa, N., additional, Baldzuhn, J., additional, Bando, T., additional, Bernard, E., additional, Castejón, F., additional, Chikaraishi, H., additional, Emoto, M., additional, Evans, T., additional, Ezumi, N., additional, Fujii, K., additional, Funaba, H., additional, Goto, M., additional, Goto, T., additional, Gradic, D., additional, Gunsu, Y., additional, Hamaguchi, S., additional, Hasegawa, H., additional, Hayashi, Y., additional, Hidalgo, C., additional, Higashiguchi, T., additional, Hirooka, Y., additional, Hishinuma, Y., additional, Horiuchi, R., additional, Ichiguchi, K., additional, Ida, K., additional, Ido, T., additional, Igami, H., additional, Ikeda, K., additional, Ishiguro, S., additional, Ishizaki, R., additional, Ishizawa, A., additional, Ito, A., additional, Ito, Y., additional, Iwamoto, A., additional, Kamio, S., additional, Kamiya, K., additional, Kaneko, O., additional, Kanno, R., additional, Kasahara, H., additional, Kato, D., additional, Kato, T., additional, Kawahata, K., additional, Kawamura, G., additional, Kisaki, M., additional, Kitajima, S., additional, Ko, W.H., additional, Kobayashi, M., additional, Kobayashi, S., additional, Kobayashi, T., additional, Koga, K., additional, Kohyama, A., additional, Kumazawa, R., additional, Lee, J.H., additional, López-Bruna, D., additional, Makino, R., additional, Masuzaki, S., additional, Matsumoto, Y., additional, Matsuura, H., additional, Mitarai, O., additional, Miura, H., additional, Miyazawa, J., additional, Mizuguchi, N., additional, Moon, C., additional, Morita, S., additional, Moritaka, T., additional, Mukai, K., additional, Muroga, T., additional, Muto, S., additional, Mutoh, T., additional, Nagasaka, T., additional, Nagayama, Y., additional, Nakajima, N., additional, Nakanishi, H., additional, Nakano, H., additional, Nakata, M., additional, Narushima, Y., additional, Nishijima, D., additional, Nishimura, A., additional, Nishimura, S., additional, Nishitani, T., additional, Nishiura, M., additional, Nobuta, Y., additional, Noto, H., additional, Nunami, M., additional, Obana, T., additional, Ogawa, K., additional, Ohdachi, S., additional, Ohno, M., additional, Ohno, N., additional, Ohtani, H., additional, Okamoto, M., additional, Oya, Y., additional, Ozaki, T., additional, Peterson, B.J., additional, Preynas, M., additional, Sagara, S., additional, Saito, K., additional, Sakaue, H., additional, Sanpei, A., additional, Satake, S., additional, Sato, M., additional, Saze, T., additional, Schmitz, O., additional, Seki, R., additional, Seki, T., additional, Sharov, I., additional, Shimizu, A., additional, Shiratani, M., additional, Shoji, M., additional, Skinner, C., additional, Soga, R., additional, Stange, T., additional, Suzuki, C., additional, Suzuki, Y., additional, Takada, S., additional, Takahata, K., additional, Takayama, A., additional, Takayama, S., additional, Takemura, Y., additional, Takeuchi, Y., additional, Tamura, H., additional, Tamura, N., additional, Tanaka, H., additional, Tanaka, K., additional, Tanaka, M., additional, Tanaka, T., additional, Tanaka, Y., additional, Toda, S., additional, Todo, Y., additional, Toi, K., additional, Toida, M., additional, Tokitani, M., additional, Tokuzawa, T., additional, Tsuchiya, H., additional, Tsujimura, T., additional, Tsumori, K., additional, Usami, S., additional, Velasco, J.L., additional, Wang, H., additional, Watanabe, T.-H., additional, Watanabe, T., additional, Yagi, J., additional, Yajima, M., additional, Yamada, H., additional, Yamada, I., additional, Yamagishi, O., additional, Yamaguchi, N., additional, Yamamoto, Y., additional, Yanagi, N., additional, Yasuhara, R., additional, Yatsuka, E., additional, Yoshida, N., additional, Yoshinuma, M., additional, Yoshimura, S., additional, and Yoshimura, Y., additional

Published
2017
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40. Caesiated H- Source Operation with Helium.

Author

Tsumori, K., Wada, M., Nakano, H., Kisaki, M., Ikeda, K., Haba, Y., Nagaoka, K., Kamio, S., Fujiwara, Y., and Osakabe, M.

Subjects
CESIUM, HYDROGEN ions, ION sources, COEXTRACTION (Chemistry), DEUTERIUM, ANIONS
Abstract

The consumption rate of cesium (Cs) for negative hydrogen (H-) ion source increases when the source operation gas is changed from hydrogen to deuterium. There was observed a clear indication that a deuterium discharge erodes Cs atoms on the plasma grid (PG) surface to increase work function and the co-extracted electron current. We have proposed a model, that the enhanced sputtering yield of Cs from the PG due to deuterium ions, which carries more kinetic energy to Cs adsorbed on the surface directly or indirectly, is the main reason for this fast dissipation of Cs. Introduction of helium (He) into discharge can verify the enhanced sputtering effect due to the lager mass ions in the source discharge. Comparing the effect due to seeded Cs before and after the He injection into discharge through Cs OES signals as well as the H- density measured with cavity ring-down method, the sputtering/evaporation enhancement due to He is estimated. Neutral atoms and positive ions in the He discharge should cause enhanced sputtering like deuterium, while the system does not generate neutron under the induction of acceleration voltage to diagnose the extracted negative ion beam. Plasma parameters of the H2 and He plasmas are investigated by diagnostics tools installed on NIFS-RNIS (National Institute for Fusion Science, Research and development Negative Ion Source) together with H- density measurement by cavity ring down. Enhanced consumption rate of Cs is compared with proposed sputtering yield data to predict the rate for deuterium operation of negative ion sources. [ABSTRACT FROM AUTHOR]

Published
2018
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41. Study of the Beam Extraction System of a Negative Ion Source with a C12A7 Electride Plasma Electrode.

Author

Kobayashi, M., Sasao, M., Kisaki, M., Eguchi, T., and Wada, M.

Subjects
PLASMA electrodes, EXTRACTION (Chemistry), ION sources, CURRENT density (Electromagnetism), HIGH voltages
Abstract

Key issues to fabricate a beam extraction system of a H- source with a plasma electrode (PE) made from C12A7 electride which has low work function were studied. Preliminary study of the H- extraction using a compact ECR ion source reveals, that high H- current can be extracted from a source without PE bias of high voltage. A bucket type with ECR source is being designed. Beam simulation for the extraction through the designed electrodes has been carried out using the OPERA code. It predicts that the optimum perveance is 0.6 mA/kV1.5, optimum acceleration to extraction voltage ratio Vacc/Vext is 4, with the minimum beam divergence of 9 mrad, which are enough to demonstrate the capability to produce a high H- current density. [ABSTRACT FROM AUTHOR]

Published
2018
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42. First measurements of beam plasma in NIFS test stand.

Author

Sartori, E., Nakano, H., Veltri, P., Kisaki, M., Pimazzoni, A., Brombin, M., Antoni, V., Cervaro, V., Ikeda, K., Tsumori, K., and Serianni, G.

Subjects
ION beams, CALORIMETERS, ELECTRON temperature, PLASMA potentials, HYDROGEN ions
Abstract

We report on the characteristics of the beam-generated plasma in the multibeamlet case of a hydrogen negative ion beam at NIFS. The plasma potential, and the energy of secondary particles in the drift region of an ion beam, offer an insight into the mechanisms that allow beam transport in low pressure gasses. The first measurements reported here were made by means of a four-gridded retarding field energy analyzer, combined with the measurement of the drain current at the beam dump, and with infrared beamlet monitoring technique. The retarding field analyzer measures the energy distributions of particles emitted radially from the beam-generated plasma [1]. The beam is dumped onto a graphite calorimeter, which is electrically insulated, so that it can be electrically biased and the collected current can be measured. The thermal image of the calorimeter is acquired during the beam pulse, thus offering a quantitative estimation of the single beamlet optics and multibeamlet focusing. Finally, the influence of the neutral gas density is studied by puffing hydrogen gas in this drift region. The measured ion and electron energy distribution functions are strongly affected by the electric bias of the calorimeter. For a 47kV, 0.3A beam, an electron temperature of 3eV at the plasma edge was found. The energy distribution of the ions for a pressure of about 0.03Pa is presented, from which the plasma potential can be inferred. [ABSTRACT FROM AUTHOR]

Published
2018
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43. Negative ion optics benchmark experiments at NIFS

Author

Veltri P., Antoni A., Agostinetti P., Brombin M., Ikeda K., Kisaki M., Nakano H., Sartori E., Serianni G., Takeiri Y., and Tsumori K.

Subjects
Neutral Beam Test Facility, NBTF, Beam Physics Simulations
Abstract

Negative ions are fundamental to produce high energy neutral beams used to he at the plasma in fusion experiments . The negative ions so urces for reactor class fusion devices represent a huge extrapolation from existing device, hence the use of modelling tools i s mandatory. In particular, the design of the neutral beam injector of the ITER experiment was strongly based on the results of n umerical codes. In this report we c ompare the models with the results of real experiments, carried out during dedicated campaigns at the R&D negative ion source (RNIS) hosted at the national institute for fusion science (NIFS), in Japan.

Published
2015

44. Recent Studies of Hydrogen Negativ e Ion Source and Beam Production for NBI in Large Helical Device

Author

Ikeda K., Agostinetti P., Brombin M., Fantz U., Geng S., Kaneko O., Kisaki M., Nagaoka K., Nakano H., Osakabe M., Sartori E., Serianni G., Takeiri Y., Tsumori K., Veltri P., Wimmer C., and Wunderlich D.

Abstract

Neutral beam injector (NBI) is an indispensable device to produce high-density and hot plasmas in fusion development machine. We have developed negative-ion-based NBI (N- NBI) in LHD, that have been operated continuously since 1998. Three N-NBIs are arranged tangentially, and was equipped with a negative hydrogen ion (H-) source which enabled high energy and high power beam injection. The nominal specication of beam energy and beam power for each N-NBI was 180 keV and 5 MW, respectively. We had achieved 16 MW beam injection by three N-NBIs in LHD experiment. Moreover, we installed two positive-ion-based neutral beam injector (P-NBI) arranged perpendicularly to the LHD. High-power (12 MW) with lower energy (40~60 keV) beam injection allowed effective ion heating and profile measurement of ion temperature by charge exchange recombination spectroscopy. A hydrogen negative ion source is a key component in N-NBI system, that will also use future NBI in ITER. Understanding of H- behavior from cesiated metal production surface to extraction aperture is an important issue to maintain high power negative ion beam. We have researched distribution of H- ions and its extraction behavior by cavity ring-down spectroscopy and a spectrally-selective imaging system, respectively, in the 1/3 scaled ion source (NIFS-RNIS). We found that H- ions widely distributed in the extraction region, and these ions constituted H- beam. Recently, we have a lot of domestic and international collaboration program for H- source. We applied a spectrally-selective imaging system in RF hydrogen negative on source in ELISE test facility in Max-Planck-Institut fur Plasmaphysik (IPP) Garching (Germany). We found clear signal response on H? emission during beam extraction. This observation will contribute to obtain behavior of H- ions in RF source which is variable output for production high power beam and optimization of beam shape in ITER source. We also observed an extracted H- beam shape in NIFS-RNIS used the mini-STRIKE system which consists of a carbon- fibre-carbon-composite (CFC) tiles and an infrared camera collaborated with Consorzio RFX (Italy). We found the clear dependence between the beam shape and operating parameters. These findings have contributed to the high performance and safety NBI operation in the LHD.

Published
2015

45. Optics of the NIFS Negative ion source test stand by infrared calorimetry and numerical modeling

Author

Veltri P., Antoni V., Agostinetti P., Brombin M., Ikeda K., Kisaki M., Nakano H., Sartori E., Serianni G., Takeiri Y., and Tsumori K.

Subjects
Physics::Accelerator Physics
Abstract

At the National Institute for Fusion Science (NIFS, Japan), neutral beams with the energy up to 15 MW are routinely injected to the hydrogen plasma confined in the Large Helical Device (LHD) using three negative ion beam-lines[1]. Together with the heating beam-lines, a test stand beamline is also operated at NIFS, to gain a better understanding of the physics regulating the formation, extraction and acceleration of negative ions, and their conversion to neutrals. The test stand is based on a 1/3-scaled negative ion source of the same arc-driven source adopted for the LHD beamline, and its acceleration system is a standard triode. The electrode grids are divided into 2 segments having slightly different geometries of the intermediate steering grid (SG) and a common multi slotted grounded grid. In this paper the beamlet optics of both systems was studied by means of an instrumented calorimeter [2] made of carbon fibre composite (CFC) tiles; the tiles were constructed making the propagation of thermal energy along the beam direction largely dominant with respect to the other directions, so that the thermal pattern on the rear plane of the tile has a strong correlation with the power profile deposited by the beamlets on the beamfacing plane of the tile. Infrared image of this thermal pattern is analysed to study the beamlet characteristics obtained in different source conditions [3]. The experimental measurements are then compared with 3D numerical simulations, in order to validate the codes, and to assess their degree of reliability. The simulations show a satisfactory agreement with the experimental results; some minor discrepancies are highlighted and their possible causes are addressed in the manuscript.

Published
2015

49. Ion beam transport: modelling and experimental measurements on a large negative ion source in view of the ITER heating neutral beam

Author

Veltri, P., primary, Sartori, E., additional, Agostinetti, P., additional, Aprile, D., additional, Brombin, M., additional, Chitarin, G., additional, Fonnesu, N., additional, Ikeda, K., additional, Kisaki, M., additional, Nakano, H., additional, Pimazzoni, A., additional, Tsumori, K., additional, and Serianni, G., additional

Published
2016
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