Experimental experience and improvement of NIO1 H− ion source

Movable electrical probes were used to diagnose the beam flux profile and potential of ion beams since the early 1960s. Experimental measurements of beam plasmas can provide essential data related to the space charge neutralization, but the current-voltage characteristics obtained from such electrical probes are dominated by beam ion impact and ion-induced secondary emission. In this work, we present an analysis of the Langmuir characteristics obtained in a negative ion beam. We identify and discuss separately the contributions to the collected current given by secondary plasma ions and electrons, stripped electrons, beam ions, and ion-induced secondary electron emission. We present the beam plasma parameters obtained at different beam energies in NIO1.

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“…In this paper, a dataset consisting of 11 CV characteristics is used. The data are obtained in the NIO1 experiment 9 (Negative Ion…”

Section: Methods To Extract Beam Plasma Parametersmentioning

confidence: 99%

Analysis of current–voltage characteristics for Langmuir probes immersed in an ion beam

Sartori

Candeloro

Serianni³

2020

Review of Scientific Instruments

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“…The Negative Ion Optimisation facility, phase 1 (NIO1) [28], is a versatile multi-aperture H2 source, with compact and modular design, capable of continuous operation. It aims at reproducing the physics conditions of the much larger ion sources, to readily verify the effects of individual source components/parameters and to compare results with simulations.…”

Section: Accompanying Programmementioning

confidence: 99%

SPIDER in the roadmap of the ITER neutral beams

Serianni

Toigo

Bigi

et al. 2019

Fusion Engineering and Design

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To reach fusion conditions and control plasma configuration in ITER, a suitable combination of additional heating and current drive systems is necessary. Among them, two Neutral Beam Injectors (NBI) will provide 33MW hydrogen/deuterium particles electrostatically accelerated to 1MeV; efficient gas-cell neutralisation at such beam energy requires negative ions, obtained by caesium-catalysed surface conversion of atoms inside the ion source. As ITER NBI requirements have never been simultaneously attained, a Neutral Beam Test Facility (NBTF) was set up at Consorzio RFX (Italy), including two experiments. MITICA is the full-scale NBI prototype with 1MeV particle energy. SPIDER, with 100keV particle energy, aims at testing and optimising the full-scale ion source: extracted beam uniformity, negative ion current density (for one hour) and beam optics (beam divergence <7mrad; beam aiming direction within 2mrad). This paper outlines the worldwide effort towards the ITER NBI realisation: the main results of the ELISE facility (IPP-Garching, Germany), equipped with a half-size source, are described along with the status of MITICA; specific issues are investigated by small specific facilities and by joint experiments at QST and NIFS (Japan). The SPIDER experiment, just come into operation, will profit from strong modelling activities, to simulate and interpret experimental scenarios, and from advanced diagnostic instruments, providing thorough plasma and beam characterisation. Finally, the results of the first experiments in SPIDER are presented, aimed at a preliminary source plasma characterisation by plasma light detectors and plasma spectroscopy.

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“…NIO1 aims at studying the source plasma and the beam production, to support the development of neutral beam injectors (NBI) for future fusion reactors (DEMO in particular). [1][2][3][4] Differently from other larger facilities in this field, NIO1 was designed to withstand plasma generation and beam extraction for several hours. [5][6][7] The structure of NIO1 is shown in the 3D section of figure 1.…”

Section: Introductionmentioning

confidence: 99%

Continuous pulse advances in the negative ion source NIO1

Barbisan,

Agnello,

Cavenago

et al. 2023

J. Inst.

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Consorzio RFX and INFN-LNL have designed, built and operated the compact radiofrequency negative ion source NIO1 (Negative Ion Optimization phase 1) with the aim of studying the production and acceleration of H- ions. In particular, NIO1 was designed to keep plasma generation and beam extraction continuously active for several hours. Since 2020 the production of negative ions at the plasma grid (the first grid of the acceleration system) has been enhanced by a Cs layer, deposited though active Cs evaporation in the source volume. For the negative ion sources applied to fusion neutral beam injectors, it is essential to keep the beam current and the fraction of co-extracted electrons stable for at least 1 h, against the consequences of Cs sputtering and redistribution operated by the plasma. The paper presents the latest results of the NIO1 source, in terms of caesiation process and beam performances during continuous (6 ÷ 7 h) plasma pulses. Due to the small dimensions of the NIO1 source (20 cm×∅10 cm), the Cs density in the volume is high (1015 ÷ 1016 m-3) and dominated by plasma-wall interaction. The maximum beam current density and minimum fraction of co-extracted electrons were respectively about 30 A/m2 and 2. Similarly to what done in other negative ion sources, the plasma grid temperature in NIO1 was raised for the first time, up to 80 °C, although this led to a minimal improvement of the beam current and to an increase of the co-extracted electron current.

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Experimental experience and improvement of NIO1 H− ion source

Cited by 6 publications

References 20 publications

Analysis of current–voltage characteristics for Langmuir probes immersed in an ion beam

Analysis of current–voltage characteristics for Langmuir probes immersed in an ion beam

SPIDER in the roadmap of the ITER neutral beams

Continuous pulse advances in the negative ion source NIO1

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