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Mieko Kashiwagi

Bio: Mieko Kashiwagi is an academic researcher from Japan Atomic Energy Agency. The author has contributed to research in topics: Beam (structure) & Ion. The author has an hindex of 23, co-authored 141 publications receiving 1594 citations.


Papers
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Journal ArticleDOI
Vanni Toigo, R. Piovan, S. Dal Bello, Elena Gaio, Adriano Luchetta, Roberto Pasqualotto, P. Zaccaria, M. Bigi, Giuseppe Chitarin, Diego Marcuzzi, N. Pomaro, Gianluigi Serianni, Piero Agostinetti, Matteo Agostini, V. Antoni, D. Aprile, C. Baltador, Marco Barbisan, M. Battistella, M. Boldrin, M. Brombin, M. Dalla Palma, A. De Lorenzi, R. Delogu, M. De Muri, F. Fellin, Alberto Ferro, A. Fiorentin, G. Gambetta, Francesco Gnesotto, Luca Grando, P. Jain, A. Maistrello, Gabriele Manduchi, Nicolò Marconato, M. Moresco, E. Ocello, M. Pavei, Simone Peruzzo, Nicola Pilan, A. Pimazzoni, M. Recchia, Andrea Rizzolo, G. Rostagni, Emanuele Sartori, M. Siragusa, Piergiorgio Sonato, A. Sottocornola, E. Spada, Silvia Spagnolo, M. Spolaore, C. Taliercio, M. Valente, Pierluigi Veltri, A. Zamengo, Barbara Zaniol, L. Zanotto, M. Zaupa, D. Boilson1, J. Graceffa1, Lennart Svensson1, B. Schunke1, H. Decamps1, M. Urbani1, M. Kushwah1, J. Chareyre1, M. J. Singh1, Tullio Bonicelli2, G. Agarici2, A. Garbuglia2, A. Masiello2, F. Paolucci2, Muriel Simon2, L. Bailly-Maitre2, E. Bragulat2, G. Gomez2, Daniel Gutierrez2, G. Mico2, J.F. Moreno2, V. Pilard2, Mieko Kashiwagi, Masaya Hanada, Hiroyuki Tobari, Kazuhiro Watanabe, T. Maejima, Atsushi Kojima, Naotaka Umeda, H. Yamanaka, A.K. Chakraborty, Ujjwal Baruah, C. Rotti, Hitesh Patel, M.V. Nagaraju, Namita Singh, A. Patel, H. Dhola, B. Raval, Ursel Fantz3, Bernd Heinemann3, W. Kraus3, S. Hanke, Volker Hauer, S. Ochoa, P. Blatchford, B. Chuilon, Y. Xue, H.P.L. de Esch, R. S. Hemsworth, Gabriele Croci4, Giuseppe Gorini4, Marica Rebai4, A. Muraro, M. Tardocchi, Marco Cavenago, Marco D’Arienzo5, Sandro Sandri5, A. Tonti 
TL;DR: The ITER Neutral Beam Test Facility (NBTF) is hosted in Padova, Italy and includes two experiments: MITICA, the full-scale prototype of the ITER heating neutral beam injector, and SPIDER, full-size radio frequency negative-ions source.
Abstract: The ITER Neutral Beam Test Facility (NBTF), called PRIMA (Padova Research on ITER Megavolt Accelerator), is hosted in Padova, Italy and includes two experiments: MITICA, the full-scale prototype of the ITER heating neutral beam injector, and SPIDER, the full-size radio frequency negative-ions source. The NBTF realization and the exploitation of SPIDER and MITICA have been recognized as necessary to make the future operation of the ITER heating neutral beam injectors efficient and reliable, fundamental to the achievement of thermonuclear-relevant plasma parameters in ITER. This paper reports on design and R&D carried out to construct PRIMA, SPIDER and MITICA, and highlights the huge progress made in just a few years, from the signature of the agreement for the NBTF realization in 2011, up to now—when the buildings and relevant infrastructures have been completed, SPIDER is entering the integrated commissioning phase and the procurements of several MITICA components are at a well advanced stage.

148 citations

Journal ArticleDOI
Vanni Toigo, D. Boilson1, Tullio Bonicelli2, R. Piovan, Masaya Hanada3, A.K. Chakraborty, G. Agarici2, V. Antoni, Ujjwal Baruah, M. Bigi, Giuseppe Chitarin, S. Dal Bello, H. Decamps1, J. Graceffa1, Mieko Kashiwagi3, R.S. Hemsworth1, Adriano Luchetta, Diego Marcuzzi, A. Masiello2, F. Paolucci2, Roberto Pasqualotto, Hitesh Patel, N. Pomaro, C. Rotti, Gianluigi Serianni, M. Simon2, M. J. Singh1, Namita Singh, Lennart Svensson1, Hiroyuki Tobari3, Kazuhiro Watanabe3, P. Zaccaria, Piero Agostinetti, Matteo Agostini, R. Andreani, D. Aprile, M. Bandyopadhyay, Marco Barbisan, M. Battistella, Paolo Bettini, P. Blatchford, M. Boldrin, Federica Bonomo, E. Bragulat2, M. Brombin, Marco Cavenago, B. Chuilon, A. Coniglio, Gabriele Croci, M. Dalla Palma, Marco D’Arienzo4, R. Dave, H.P.L. de Esch, A. De Lorenzi, M. De Muri, R. Delogu, H. Dhola, Ursel Fantz5, F. Fellin, L. Fellin, Alberto Ferro, A. Fiorentin, N. Fonnesu, P. Franzen5, M. Fröschle5, Elena Gaio, G. Gambetta, G. Gomez2, Francesco Gnesotto, Giuseppe Gorini6, Luca Grando, Veena Gupta, D. Gutierrez2, S. Hanke, Christopher D. Hardie, Bernd Heinemann5, Atsushi Kojima3, W. Kraus5, T. Maeshima3, A. Maistrello, Gabriele Manduchi, Nicolò Marconato, G. Mico2, J.F. Moreno2, M. Moresco, A. Muraro, V. N. Muvvala, Riccardo Nocentini5, E. Ocello, S. Ochoa, D. Parmar, A. Patel, M. Pavei, Simone Peruzzo, Nicola Pilan, V. Pilard2, M. Recchia, R. Riedl5, Andrea Rizzolo, G. Roopesh, G. Rostagni, Sandro Sandri4, Emanuele Sartori, P. Sonato, A. Sottocornola, Silvia Spagnolo, M. Spolaore, C. Taliercio, M. Tardocchi, A. Thakkar, Naotaka Umeda3, M. Valente, Pierluigi Veltri, Ashish Yadav, H. Yamanaka3, A. Zamengo, Barbara Zaniol, L. Zanotto, M. Zaupa 
TL;DR: In this paper, the authors present a general overview of the test facility and of the status of development of the main components at this important stage of the overall development, focusing on the latest and most critical issues, regarding both physics and technology, describing the identified solutions.
Abstract: The ITER project requires additional heating by two neutral beam injectors, each accelerating to 1 MV a 40 A beam of negative deuterium ions, to deliver to the plasma a power of about 17 MW for one hour. As these requirements have never been experimentally met, it was recognized as necessary to setup a test facility, PRIMA (Padova Research on ITER Megavolt Accelerator), in Italy, including a full-size negative ion source, SPIDER, and a prototype of the whole ITER injector, MITICA, aiming to develop the heating injectors to be installed in ITER. This realization is made with the main contribution of the European Union, through the Joint Undertaking for ITER (F4E), the ITER Organization and Consorzio RFX which hosts the Test Facility. The Japanese and the Indian ITER Domestic Agencies (JADA and INDA) participate in the PRIMA enterprise; European laboratories, such as IPP-Garching, KIT-Karlsruhe, CCFE-Culham, CEA-Cadarache and others are also cooperating. Presently, the assembly of SPIDER is on-going and the MITICA design is being completed. The paper gives a general overview of the test facility and of the status of development of the MITICA and SPIDER main components at this important stage of the overall development; then it focuses on the latest and most critical issues, regarding both physics and technology, describing the identified solutions.

111 citations

Journal ArticleDOI
TL;DR: The purpose of MITICA is to demonstrate that all operational parameters of the ITER HNB accelerator can be experimentally achieved, thus establishing a large step forward in the performances of neutral beam injectors in comparison with the present experimental devices.
Abstract: The ITER Neutral Beam Test Facility (PRIMA) is presently under construction at Consorzio RFX (Padova, Italy). PRIMA includes two experimental devices: an ITER-size ion source with low voltage extraction, called SPIDER, and the full prototype of the whole ITER Heating Neutral Beams (HNBs), called MITICA.The purpose of MITICA is to demonstrate that all operational parameters of the ITER HNB accelerator can be experimentally achieved, thus establishing a large step forward in the performances of neutral beam injectors in comparison with the present experimental devices.The design of the MITICA extractor and accelerator grids, here described in detail, was developed using an integrated approach, taking into consideration at the same time all the relevant physics and engineering aspects. Particular care was taken also to support and validate the design on the basis of the expertise and experimental data made available by the collaborating neutral beam laboratories of CEA, IPP, CCFE, NIFS and JAEA. Considering the operational requirements and the other physics constraints of the ITER HNBs, the whole design has been thoroughly optimized and improved. Furthermore, specific innovative concepts have been introduced.

86 citations

Journal ArticleDOI
TL;DR: The design of the ITER tokamak is described in this article, with an initial complement of two beamlines injecting parallel to the direction of the current arising from the transformer effect, and with the possibility of eventually adding a third beamline also in the co-current direction.

68 citations

Journal ArticleDOI
TL;DR: In this paper, the physics design of the accelerator for the heating neutral beamline on ITER is now finished and the considerations and choices which constitute the basis of this design are described and compared.
Abstract: The physics design of the accelerator for the heating neutral beamline on ITER is now finished and this paper describes the considerations and choices which constitute the basis of this design. Equal acceleration gaps of 88 mm have been chosen to improve the voltage holding capability while keeping the beam divergence low. Kerbs (metallic plates around groups of apertures, attached to the downstream surface of the grids) are used to compensate for the beamlet–beamlet interaction and to point the beamlets in the right direction. A novel magnetic configuration is employed to compensate for the beamlet deflection caused by the electron suppression magnets in the extraction grid. A combination of long-range and short-range magnetic fields is used to reduce electron leakage between the grids and limit the transmitted electron power to below 800 kW.

58 citations


Cited by
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Journal ArticleDOI
TL;DR: The ITER neutral beam (NB) injectors are the first injectors that will have to operate under conditions and constraints similar to those that will be encountered in a fusion reactor as discussed by the authors.
Abstract: The ITER neutral beam (NB) injectors are the first injectors that will have to operate under conditions and constraints similar to those that will be encountered in a fusion reactor. These injectors will have to operate in a hostile radiation environment and they will become highly radioactive due to the neutron flux from ITER. The injectors will use a single large ion source and accelerator that will produce 40?A 1?MeV D? beams for pulse lengths of up to 3600?s.Significant design changes have been made to the ITER heating NB (HNB) injector over the past 4 years. The main changes are: Modifications to allow installation and maintenance of the beamline components with an overhead crane. The beam source vessel shape has been changed and the beam source moved to allow more space for the connections between the 1?MV bushing and the beam source. The RF driven negative ion source has replaced the filamented ion source as the reference design. The ion source and extractor power supplies will be located in an air insulated high voltage (?1?MV) deck located outside the tokamak building instead of inside an SF6 insulated HV deck located above the injector. Introduction of an all metal absolute valve to prevent any tritium in the machine to escape into the NB cell during maintenance. This paper describes the status of the design as of December 2008 including the above mentioned changes.The very important power supply system of the neutral beam injectors is not described in any detail as that merits a paper beyond the competence of the present authors.The R&D required to realize the injectors described in this paper must be carried out on a dedicated neutral beam test facility, which is not described here.

432 citations

Journal ArticleDOI
R. C. Wolf1
TL;DR: In this article, internal transport barriers in tokamak plasmas are explored in order to improve confinement and stability beyond the reference scenario, used for the ITER extrapolation, and to achieve higher bootstrap current fractions as an essential part of non-inductive current drive.
Abstract: Internal transport barriers in tokamak plasmas are explored in order to improve confinement and stability beyond the reference scenario, used for the ITER extrapolation, and to achieve higher bootstrap current fractions as an essential part of non-inductive current drive. Internal transport barriers are produced by modifications of the current profile using external heating and current drive effects, often combined with partial freezing of the initial skin current profile. Thus, formerly inaccessible ion temperatures and QDTeq values have been (transiently) achieved. The present paper reviews the state of the art of these techniques and their effects on plasma transport in view of optimizing the confinement properties. Implications and limits for possible steady state operations and extrapolation to burning plasmas are discussed.

323 citations

Journal ArticleDOI
TL;DR: Negative hydrogen/deuterium ions can be formed by processes occurring in the plasma volume and on surfaces facing the plasma as mentioned in this paper, and the principal mechanisms leading to the formation of these negative ions are dissociative electron attachment to ro-vibrationally excited hydrogen and deuterium molecules when the reaction takes place in the volume, and direct electron transfer from the low work function metal surface to the hydrogen atoms when formation occurs on the surface.
Abstract: Negative hydrogen/deuterium ions can be formed by processes occurring in the plasma volume and on surfaces facing the plasma. The principal mechanisms leading to the formation of these negative ions are dissociative electron attachment to ro-vibrationally excited hydrogen/deuterium molecules when the reaction takes place in the plasma volume, and the direct electron transfer from the low work function metal surface to the hydrogen/deuterium atoms when formation occurs on the surface. The existing theoretical models and reported experimental results on these two mechanisms are summarized. Performance of the negative hydrogen/deuterium ion sources that emerged from studies of these mechanisms is reviewed. Contemporary negative ion sources do not have negative ion production electrodes of original surface type sources but are operated with caesium with their structures nearly identical to volume production type sources. Reasons for enhanced negative ion current due to caesium addition to these sources are discussed.

239 citations

Journal ArticleDOI
TL;DR: In this paper, the authors describe the design of the ITER HNB injectors, but not the associated power supplies, cooling system, cryogenic system etc, or the high voltage bushing which separates the vacuum of the beamline from the high pressure SF6 of the 1 MV transmission line, through which the power, gas and cooling water are supplied to the beam source.
Abstract: The heating neutral beam injectors (HNBs) of ITER are designed to deliver 16.7 MW of 1 MeV D0 or 0.87 MeV H0 to the ITER plasma for up to 3600 s. They will be the most powerful neutral beam (NB) injectors ever, delivering higher energy NBs to the plasma in a tokamak for longer than any previous systems have done. The design of the HNBs is based on the acceleration and neutralisation of negative ions as the efficiency of conversion of accelerated positive ions is so low at the required energy that a realistic design is not possible, whereas the neutralisation of H− and D− remains acceptable (≈56%). The design of a long pulse negative ion based injector is inherently more complicated than that of short pulse positive ion based injectors because: • negative ions are harder to create so that they can be extracted and accelerated from the ion source; • electrons can be co-extracted from the ion source along with the negative ions, and their acceleration must be minimised to maintain an acceptable overall accelerator efficiency; • negative ions are easily lost by collisions with the background gas in the accelerator; • electrons created in the extractor and accelerator can impinge on the extraction and acceleration grids, leading to high power loads on the grids; • positive ions are created in the accelerator by ionisation of the background gas by the accelerated negative ions and the positive ions are back-accelerated into the ion source creating a massive power load to the ion source; • electrons that are co-accelerated with the negative ions can exit the accelerator and deposit power on various downstream beamline components. The design of the ITER HNBs is further complicated because ITER is a nuclear installation which will generate very large fluxes of neutrons and gamma rays. Consequently all the injector components have to survive in that harsh environment. Additionally the beamline components and the NB cell, where the beams are housed, will be activated and all maintenance will have to be performed remotely. This paper describes the design of the HNB injectors, but not the associated power supplies, cooling system, cryogenic system etc, or the high voltage bushing which separates the vacuum of the beamline from the high pressure SF6 of the high voltage (1 MV) transmission line, through which the power, gas and cooling water are supplied to the beam source. Also the magnetic field reduction system is not described.

205 citations