Design of the RF ion source for the ITER NBI

Marcuzzi, D.; Agostinetti, P.; Palma, M. Dalla; Falter, H.; Heinemann, B.; Riedl, R.

doi:10.1016/j.fusengdes.2007.07.033

Cited by 35 publications

(18 citation statements)

References 7 publications

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“…But these sources have in common that they rely on plasma generation in a cylindrical discharge vessel via inductive coupling with a helical antenna (due to the large size the ITER sources is going to be equipped with 8 discharge vessels, the so-called drivers). However, in order to achieve the required H − currents very high RF powers are needed: for the ITER source a maximum RF power of up to 100 kW per driver is foreseen (operating pressure 0.3 Pa, working gas hydrogen and deuterium, RF frequency 1 MHz, driver volume ≈ 7.5 l) [1,2]; for the Linac4 source up to 100 kW are used (IS-02, operating pressure several Pa, working gas hydrogen, RF frequency 2 MHz, discharge vessel volume ≈ 0.25 l) [3]. These high RF powers pose strong demands on the RF circuit and generators which makes a reduction of the required powers very desirable.…”

Section: Introductionmentioning

confidence: 99%

“…However, Helicon discharges are typically operated in long and thin discharge vessels using rare gases (especially argon). The applicability of Helicon coupling to hydrogen or deuterium has not been investigated systematically yet 1 . In order to investigate and optimize Helicon coupling for H 2 and D 2 the laboratory experiment CHARLIE (Concept studies for Helicon Assisted RF Low pressure Ion sourcEs) has been set up [9].…”

Section: Introductionmentioning

confidence: 99%

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Alternative RF coupling configurations for H− ion sources

Briefi

Gutmann

Fantz

2015

AIP Conference Proceedings

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Abstract. RF heated sources for negative hydrogen ions both for fusion and accelerators require very high RF powers in order to achieve the required H − current what poses high demands on the RF generators and the RF circuit. Therefore it is highly desirable to improve the RF efficiency of the sources. This could be achieved by applying different RF coupling concepts than the currently used inductive coupling via a helical antenna, namely Helicon coupling or coupling via a planar ICP antenna enhanced with ferrites. In order to investigate the feasibility of these concepts, two small laboratory experiments have been set up. The PlanICE experiment, where the enhanced inductive coupling is going to be investigated, is currently under assembly. At the CHARLIE experiment systematic measurements concerning Helicon coupling in hydrogen and deuterium are carried out. The investigations show that a prominent feature of Helicon discharges occurs: the so-called low-field peak. This is a local improvement of the coupling efficiency at a magnetic field strength of a few mT which results in an increased electron density and dissociation degree. The full Helicon mode has not been achieved yet due to the limited available RF power and magnetic field strength but it might be sufficient for the application of the coupling concept to ion sources to operate the discharge in the low-field-peak region.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Alternative RF coupling configurations for H− ion sources

Briefi

Gutmann

Fantz

2015

AIP Conference Proceedings

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“…For example, at the ion source of the ITER neutral beam heating system which will be equipped with 8 cylindrical discharge vessels, the so-called drivers, a maximum RF power of 100 kW per driver is planned [1,2]. A reduction of the RF power would be highly beneficial, as such high powers pose strong demands on all components of the RF circuit and the generators.…”

Section: Introductionmentioning

confidence: 99%

Investigation of the RF efficiency of inductively coupled hydrogen plasmas at 1 MHz

Rauner

Mattei

Briefi

et al. 2017

AIP Conference Proceedings

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Abstract. The power requirements of RF heated sources for negative hydrogen ions in fusion are substantial, which poses strong demands on the generators and components of the RF circuit. Consequently, an increase of the RF coupling efficiency would be highly beneficial. Fundamental investigations of the RF efficiency in inductively coupled hydrogen and deuterium discharges in cylindrical symmetry are conducted at the lab experiment CHARLIE. The experiment is equipped with several diagnostics including optical emission spectroscopy and a movable floating double probe to monitor the plasma parameters. The presented investigations are performed in hydrogen at a varying pressure between 0.3 and 10 Pa, utilizing a conventional helical ICP coil driven at a frequency of 1 MHz and a fixed power of 520 W for plasma generation. The coupling efficiency is strongly affected by the variation in pressure, reaching up to 85 % between 1 and 3 Pa while dropping down to only 50 % at 0.3 Pa, which is the relevant operating pressure for negative hydrogen ion sources for fusion. Due to the lower power coupling, also the measured electron density at 0.3 Pa is only 5 · 10 16 m −3 , while it reaches up to 2.5 · 10 17 m −3 with increasing coupling efficiency. In order to gain information on the spatially resolved aspects of RF coupling and plasma heating which are not diagnostically accessible, first simulations of the discharge by an electromagnetic Particle-In-Cell Monte Carlo collision method have been conducted and are compared to the measurement data. At 1 Pa, the simulated data corresponds well to the results of both axially resolved probe measurements and radially resolved emission profiles obtained via OES. Thereby, information regarding the radial distribution of the electron density and mean energy is provided, revealing a radial distribution of the electron density which is well described by a Bessel profile.

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“…Radio frequency (RF) electrical power will excite plasmas of a negative hydrogen ion (H − ) sources for neutral beam injection system in the current ITER planning [1]. Test ion sources utilize RF power at MHz range to produce high current density H − beams [2].…”

Section: Introductionmentioning

confidence: 99%

Development of a 14 GHz Microwave H− Source

Wada

Demura

Kasuya

et al. 2011

Plasma and Fusion Research

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Microwave power at 14 GHz has excited a H 2 plasma in a 2 cm inner diameter 9 cm long alumina tube to generate negative hydrogen ion (H − ) beam. A pair of permanent magnets created a magnetic field with the intensity corresponding to an electron cyclotron resonance condition for the input microwave. The ion source produced stable plasmas with the H 2 pressure more than 0.5 Pa, while the amount of H − current decreased exponentially against increasing ion source pressure above 0.6 Pa. When the source produced H − beam with constant H 2 pressure at 0.6 Pa, the H − beam current saturated against the increase of microwave power above 200 W. These characteristics of the H − beam current indicate poor transport of vibrationally excited hydrogen molecules and that of H − to the ion extraction electrode.

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Design of the RF ion source for the ITER NBI

Cited by 35 publications

References 7 publications

Alternative RF coupling configurations for H− ion sources

Alternative RF coupling configurations for H− ion sources

Investigation of the RF efficiency of inductively coupled hydrogen plasmas at 1 MHz

Development of a 14 GHz Microwave H− Source

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