Operation of the negative-ion based NBI for JT-60U

Kuriyama, M.; Akino, N.; Aoyagi, T.; Ebisawa, N.; Isozaki, N.; Honda, Akira; Inoue, Takashi; Itoh, Takaò; Kawai, M.; Kazawa, M.; Koizumi, J.; Mogaki, K.; Ohara, Y.; Ohga, T.; Okumura, Y.; Oohara, H.; Ohshima, K.; Satoh, F.; Takenouchi, T.; Toyokawa, Yoichi; Usui, K.; Watanabe, K.; Yamamoto, Masahiro; Yamazaki, Takeshi; Zhou, Chaobiao

doi:10.1016/s0920-3796(98)00183-5

Cited by 36 publications

(14 citation statements)

References 4 publications

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“…The maximum neutralisation yield for negative-ion deuterium beams is below 0.58, independent of the energy in the range 200 keV-1 MeV. One should note that the available cross sectional data to calculate the yield is given with ±25% accuracy, with experimental measurements supporting this result only up to 400 keV D − [79].…”

Section: Neutralisationmentioning

confidence: 92%

Neutralisation and transport of negative ion beams: physics and diagnostics

Serianni¹,

Agostinetti²,

Agostini³

et al. 2017

New J. Phys.

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Neutral beam injection is one of the most important methods of plasma heating in thermonuclear fusion experiments, allowing the attainment of fusion conditions as well as driving the plasma current. Neutral beams are generally produced by electrostatically accelerating ions, which are neutralised before injection into the magnetised plasma. At the particle energy required for the most advanced thermonuclear devices and particularly for ITER, neutralisation of positive ions is very inefficient so that negative ions are used. The present paper is devoted to the description of the phenomena occurring when a high-power multi-ampere negative ion beam travels from the beam source towards the plasma. Simulation of the trajectory of the beam and of its features requires various numerical codes, which must take into account all relevant phenomena. The leitmotiv is represented by the interaction of the beam with the background gas. The main outcome is the partial neutralisation of the beam particles, but ionisation of the background gas also occurs, with several physical and technological consequences. Diagnostic methods capable of investigating the beam properties and of assessing the relevance of the various phenomena will be discussed. Examples will be given regarding the measurements collected in the small flexible NIO1 source and regarding the expected results of the prototype of the neutral beam injectors for ITER. The tight connection between measurements and simulations in view of the operation of the beam is highlighted. operating in the existing tokamaks. Consequently, PRIMA, the ITER Neutral Beam Test Facility [2], was set up to constitute a test-bed, where the solutions to all the issues related to the achievement of full performances in the heating NBI system for ITER are going to be addressed and optimised, particularly regarding critical aspects like density and uniformity of the extracted negative ion current, high voltage holding and heat loads on the components [3]. Megavolt ITER Injector Concept Advancement (MITICA) is the full-scale prototype of the ITER NBIs [4]; it includes an RF-driven plasma source for the production of negative ions and should operate at a pressure as low as 0.3 Pa in hydrogen or deuterium gasses. The negative ions are produced on the surface of the grid (Plasma Grid, PG) that closes the plasma region; their production is enhanced thanks to a thin caesium layer continuously deposited over the PG by evaporation. Negative ions are extracted through the 1280 apertures in the PG by application of a suitable positive voltage to the extraction grid (EG), located just downstream of the PG. The RF plasma source operates at an applied electric potential of about −1 MV. Five additional acceleration grids (AG1, AG2, AG3, AG4, GG), at intermediate electric potential increasing by 200 kV steps, are located downstream with respect to the EG, thus constituting a 5-stage electrostatic accelerator. The resulting negative ion beam at 1 MeV, after passing through a gas cell neutraliser and an electro...

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Section: Neutralisationmentioning

confidence: 92%

Neutralisation and transport of negative ion beams: physics and diagnostics

Serianni¹,

Agostinetti²,

Agostini³

et al. 2017

New J. Phys.

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“…Table 1 shows the major specifications of the N-NBI system in JT-60U [118]. Since then, progress has been made to increase beam voltage by conditioning [119], to improve ion source uniformity [120,121] and to reduce heat load to the electrodes [122,123]. Table 1.…”

Section: Demonstration Of Current Drive With N-nbimentioning

confidence: 99%

A Review of Fusion and Tokamak Research Towards Steady-State Operation: A JAEA Contribution

Kikuchi

2010

Energies

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Providing a historical overview of 50 years of fusion research, a review of the fundamentals and concepts of fusion and research efforts towards the implementation of a steady state tokamak reactor is presented. In 1990, a steady-state tokamak reactor (SSTR) best utilizing the bootstrap current was developed. Since then, significant efforts have been made in major tokamaks, including JT-60U, exploring advanced regimes relevant to the steady state operation of tokamaks. In this paper, the fundamentals of fusion and plasma confinement, and the concepts and research on current drive and MHD stability of advanced tokamaks towards realization of a steady-state tokamak reactor are reviewed, with an emphasis on the contributions of the JAEA. Finally, a view of fusion energy utilization in the 21st century is introduced.

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“…[9][10][11][12] The response frequency of the pair-ion plasma is limited to narrow bandwidths of below 50 kHz because of the massive ions. The research and development of negative-ion sources have been extensively performed for more than 20 years in connection with neutral beam injection heating for fusion-oriented plasmas [13][14][15][16] and ion guns for proton accelerators. Several difficulties exist in the development of this plasma source that must be overcome.…”

Section: Introductionmentioning

confidence: 99%