Status of the ITER heating neutral beam system

Hemsworth, R.; Decamps, Hans; Graceffa, J.; Schunke, B.; Tanaka, Masanobu; Dremel, M.; Tanga, A.; Esch, H.P.L. de; Geli, F.; Milnes, J.; Inoue, Takashi; Marcuzzi, D.; Sonato, P.; Zaccaria, P.

doi:10.1088/0029-5515/49/4/045006

Cited by 441 publications

(296 citation statements)

References 33 publications

(57 reference statements)

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“…Indeed, one of the heating strategies of a magnetically confined plasma in tokamaks uses high energy hydrogen or deuterium atoms accelerated by the electrostatic field of a high voltage system, the performance of which is severely limited by damaging electron currents induced by field emission. [2][3][4] The intensity of such a field emission current can be reduced by raising the pressure in the vacuum system, typically from high or ultrahigh vacuum to pressures of the order of 10 À4 À 10 À2 Pa. [5][6][7][8][9] This effect has been known for quite some time 10,11 and has been investigated recently in detail for tungsten carbide and tungsten cathodes. [12][13][14] These changes in field emission intensity with ambient pressure are related to modifications of the cathode surface state at some unknown scale, which may be the micrometer size scale or an even smaller one.…”

Section: Introductionmentioning

confidence: 99%

Static electric field enhancement in nanoscale structures

Lepetit

Lemoine

Márquez-Mijares

2016

Journal of Applied Physics

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We study the effect of local atomic-and nano-scale protrusions on field emission and, in particular, on the local field enhancement which plays a key role as known from the Fowler-Nordheim model of electronic emission. We study atomic size defects which consist of right angle steps forming an infinite length staircase on a tungsten surface. This structure is embedded in a 1 GV/m ambient electrostatic field. We perform calculations based upon density functional theory in order to characterize the total and induced electronic densities as well as the local electrostatic fields taking into account the detailed atomic structure of the metal. We show how the results must be processed to become comparable with those of a simple homogeneous tungsten sheet electrostatic model. We also describe an innovative procedure to extrapolate our results to nanoscale defects of larger sizes, which relies on the microscopic findings to guide, tune, and improve the homogeneous metal model, thus gaining predictive power. Furthermore, we evidence analytical power laws for the field enhancement characterization. The main physics-wise outcome of this analysis is that limited field enhancement is to be expected from atomic-and nano-scale defects. Published by AIP Publishing.

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Section: Introductionmentioning

confidence: 99%

Static electric field enhancement in nanoscale structures

Lepetit

Lemoine

Márquez-Mijares

2016

Journal of Applied Physics

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“…In order to provide additional heating power and current drive for the international nuclear fusion experiment ITER presently under construction in Cadarache (France), a new neutral beam injection system is being developed [1]. In ITER, two neutral beam injectors will provide about 17 MW of heating power each by means of injection of neutral particles which are accelerated up to 1 MeV.…”

Section: Introductionmentioning

confidence: 99%

Advanced ion beam calorimetry for the test facility ELISE

Nocentini

Bonomo

Pimazzoni

et al. 2015

AIP Conference Proceedings

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Abstract. The negative ion source test facility ELISE (Extraction from a Large Ion Source Experiment) is in operation since beginning of 2013 at the Max-Planck-Institut für Plasmaphysik (IPP) in Garching bei München. The large radio frequency driven ion source of ELISE is about 1x1 m 2 in size (1/2 the ITER source) and can produce a plasma for up to 1 h. Negative ions can be extracted and accelerated by an ITER-like extraction system made of 3 grids with an area of 0.1 m 2 , for 10 s every 3 minutes. A total accelerating voltage of up to 60 kV is available, i.e. a maximum ion beam power of about 1.2 MW can be produced. ELISE is equipped with several beam diagnostic tools for the evaluation of the beam characteristics. In order to evaluate the beam properties with a high level of detail, a sophisticated diagnostic calorimeter has been installed in the test facility at the end of 2013, starting operation in January 2014. The diagnostic calorimeter is split into 4 copper plates with separate water calorimetry for each of the plates. Each calorimeter plate is made of 15x15 copper blocks, which act as many separate inertial calorimeters and are attached to a copper plate with an embedded cooling circuit. The block geometry and the connection with the cooling plate are optimized to accurately measure the time-averaged power of the 10 s ion beam. The surface of the blocks is covered with a black coating that allows infrared (IR) thermography which provides a 2D profile of the beam power density. In order to calibrate the IR thermography, 48 thermocouples are installed in as many blocks, arranged in two vertical and two horizontal rows. The paper describes the beam calorimetry in ELISE, including the methods used for the IR thermography, the water calorimetry and the analytical methods for beam profile evaluation. It is shown how the maximum beam inhomogeneity amounts to 13% in average. The beam divergence derived by IR thermography ranges between 1° and 4° and correlates relatively well with the values measured by beam emission spectroscopy with up to 30% difference. It has also been observed that the beam inhomogeneity decreases with lower beam divergence.

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“…However, pulse length of the negative ion beam is limited by the heat loads of the acceleration grids and beam line components. Especially, beam halo can contribute to the heat loads even at the optimum perveance for the beam core [1,2]. Studies using the 2D3V-PIC (two dimension in real space and three dimension in velocity space)·(Particle In Cell), and 3D3V-PIC (three dimension in real space and three dimension in velocity space) model have been done, aiming to understand the extraction mechanisms of H − ions from the negative ion source, [3,4,5].…”

Section: Introductionmentioning

confidence: 99%

Study of the negative ion extraction mechanism from a double-ion plasma in negative ion sources

Goto

Miyamoto

Nishioka

et al. 2015

AIP Conference Proceedings

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Study of ion-ion plasma formation in negative ion sources by a three-dimensional in real space and three-dimensional in velocity space particle in cell model Journal of Applied Physics 119, 023302 (2016) Abstract. We have developed a 2D3V-PIC model of the extraction region, aiming to clarify the basic extraction mechanism of H − ions from the double-ion plasma in H − negative ion sources. The result shows the same tendency of the H − ion density n H − as that observed in the experiments, i.e., n H − in the upstream region away from the plasma meniscus (H − emitting surface) has been reduced by applying the extraction voltage. At the same time, relatively slow temporal oscillation of the electric potential compared with the electron plasma frequency has been observed in the extraction region. Results of the systematic study using a 1D3V-PIC model with the uniform magnetic field confirm the result that the electrostatic oscillation is identified to be lower hybrid wave. The effect of this oscillation on the H − transport will be studied in the future.

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Status of the ITER heating neutral beam system

Cited by 441 publications

References 33 publications

Static electric field enhancement in nanoscale structures

Static electric field enhancement in nanoscale structures

Advanced ion beam calorimetry for the test facility ELISE

Study of the negative ion extraction mechanism from a double-ion plasma in negative ion sources

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