Low-field helicon discharges

Chen, F F; Jiang, Xicheng; Evans, J. D.; Tynan, G. R.; Arnush, Donald

doi:10.1088/0741-3335/39/5a/038

Cited by 44 publications

(29 citation statements)

References 5 publications

(4 reference statements)

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“…In addition, the position of the low-field peak is shifted to lower magnetic field strengths for lower pressure: for example for deuterium the low-field peak position is located at around 4 mT at 1 Pa, at 3.5 mT for 0.5 Pa and at 2.5 mT at 0.3 Pa. This behavior has also been observed in rare gas Helicon discharges [7] but the reason for it is still unclear as well.…”

Section: Behavior Of the Low-field Peakmentioning

confidence: 72%

“…The concept is generally known to produce rare gas discharges with very high efficiency [5,6]. Another prominent feature is the enhancement of the coupling efficiency at a few mT external magnetic field strength, the so-called low-field peak [7], which could be enough improvement regarding the application at ion sources. For the utilization of Helicon coupling, the basic geometry of the ion sources has not to be altered, as both the driver in ion sources for fusion and the discharge vessel at ion sources for accelerators are cylindrical; only an additional magnetic field and a differently shaped antenna have to be applied.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

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: Behavior Of the Low-field Peakmentioning

confidence: 72%

Section: Introductionmentioning

confidence: 99%

Alternative RF coupling configurations for H− ion sources

Briefi

Gutmann

Fantz

2015

AIP Conference Proceedings

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“…A standard ICP antenna can be exchanged by a helicon antenna (Nagoya type III) which favors together with an axial magnetic field the |m| = 1 helicon mode for propagation. Instead of aiming to operate in the full helicon mode for which several 100 mT are required, the investigations are focussed to achieve the better coupling due to the so-called low-field peak [19]. It has already been demonstrated that the low-field peak appears below 10 mT in hydrogen and deuterium plasmas at the relevant source pressure, showing that in the peak a higher dissociation degrees and plasma densities are achieved [20].…”

Section: Randd On Innovative Ion Sourcesmentioning

confidence: 99%

Conceptual design of the beam source for the DEMO Neutral Beam Injectors

et al. 2016

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DEMO (DEMOnstration Fusion Power Plant) is a proposed nuclear fusion power plant that is intended to follow the ITER experimental reactor. The main goal of DEMO will be to demonstrate the possibility to produce electric energy from the fusion reaction. The injection of high energy neutral beams is one of the main tools to heat the plasma up to fusion conditions. A conceptual design of the Neutral Beam Injector (NBI) for the DEMO fusion reactor, is currently being developed by Consorzio RFX in collaboration with other European research institutes. High efficiency and low recirculating power, which are fundamental requirements for the success of DEMO, have been taken into special consideration for the DEMO NBI. Moreover, particular attention has been paid to the issues related to reliability, availability, maintainability and inspectability. A conceptual design of the beam source for the DEMO NBI is here presented featuring 20 sub-sources (two adjacent columns of 10 sub-sources each), following a modular design concept, with each sub-source featuring its radio frequency driver, capable of increasing the reliability and availability of the DEMO NBI. Copper grids with increasing size of the apertures have been adopted in the accelerator, with three main layouts of the apertures (circular apertures, slotted apertures and frame-like apertures for each sub-source). This design, permitting to significantly decrease the stripping losses in the accelerator without spoiling the beam optics, has been investigated with a self-consistent model able to study at the same time the magnetic field, the electrostatic field and the trajectory of the negative ions. Moreover, the status on the R&D carried out in Europe on the ion sources is presented.

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“…A second RF generator serves for substrate biasing. The substrate was 600 400 mm Chen et al have described a large array of helicon sources [65].…”

Section: A Radial Profilesmentioning

confidence: 99%