Development of a versatile multiaperture negative ion source

Cavenago, M.; Kulevoy, T. V.; Petrenko, S. V.; Serianni, G.; Antoni, V.; Bigi, M.; Fellin, F.; Recchia, M.; Veltri, P.

doi:10.1063/1.3670350

Cited by 26 publications

(11 citation statements)

References 13 publications

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“…12 NIO1 consists of an ion source from which 9 beamlets of 15 mA each of H − are accelerated up to 60 kV. Particles are extracted through the apertures of a plasma grid (PG) and their acceleration is provided by an extraction grid (EG) and a post-acceleration grid (PA).…”

Section: Results and Future Perspectivesmentioning

confidence: 99%

A 2D Particle in Cell model for ion extraction and focusing in electrostatic accelerators

Veltri¹,

Cavenago

Serianni³

2013

Review of Scientific Instruments

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Negative ions are fundamental to produce intense and high energy neutral beams used to heat the plasma in fusion devices. The processes regulating the ion extraction involve the formation of a sheath on a scale comparable to the Debye length of the plasma. On the other hand, the ion acceleration as a beam is obtained on distances greater than λD. The paper presents a model for both the phases of ion extraction and acceleration of the ions and its implementation in a numerical code. The space charge of particles is deposited following usual Particle in Cell codes technique, while the field is solved with finite element methods. Some hypotheses on the beam plasma transition are described, allowing to model both regions at the same time. The code was tested with the geometry of the NIO1 negative ions source, and the results are compared with existing ray tracing codes and discussed.

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Section: Results and Future Perspectivesmentioning

confidence: 99%

A 2D Particle in Cell model for ion extraction and focusing in electrostatic accelerators

Veltri¹,

Cavenago

Serianni³

2013

Review of Scientific Instruments

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“…A complete description of the system is available in ref. [6]. For larger beam power 𝐼 𝑎 𝑉 𝑠 > 0.5 kW where 𝐼 𝑎 is the total beam current, a removable Faraday cup is being built (to replace CFC tile) and a fixed calorimeter will be placed at diagnostic tube end.…”

Section: Jinst 18 C10012mentioning

confidence: 99%

Observation of beamlet displacement and parallelism in NIO1

Ugoletti,

Cavenago,

Agnello

et al. 2023

J. Inst.

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In the compact radiofrequency negative ion source NIO1 (Negative Ion Optimization phase 1), beamlet images are recorded from visible light monochrome cameras, for which several mounting positions are available. For two cameras, named CAM1 and CAM2, looking in directions perpendicular to each other and to the z axis of the beam drift tube, an extensive database of images is available, with methods and results of analysis discussed here. All NIO1 beamlets, arranged in a 3 × 3 matrix, are extracted, so CAM1 can record 3 beamlet projection groups and CAM2 also. Both cameras can be used to estimate the beam optics, depending on extracted beamlet currents, their uniformity and applied voltages; moreover CAM1 shows the filter current effects, while CAM2 images may give information on the deflection field (due to magnets inserted in the extraction grid EG and the post-acceleration grid PA). Light reflection is reduced by careful set-up, and by considering image central portion for analysis. Image luminosity can be simply fitted by Gaussian shapes, when the 3 projection groups are fairly separated. This analysis allows to estimate beamlet displacement and deflection. In general, optional algorithms for noise rejection and pre-smoothing for improving automatic recognizing of beamlet peaks is discussed, as well as the classes of available fits. Results for beamlet size, deflection and rms divergence are reported for selected datasets (within the 10 or 20 mrad goal). In some datasets, beamlet convergence was observed, indicating the need for further analysis and beam optics adjustments.

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“…Four different groups are working on 3D codes with reduced domains: the code developed at Keio University, Japan ("Keio-BFX") is applied mainly for investigating the formation of the ion-ion plasma [56] close to the extraction system as well as for investigations on the meniscus formation [57,58]. The 3D code by CNR-Nanotec, Bari, Italy ("Bari-Ex"), has been lately applied [59] for modelling the extraction system of the small ion source test bed NIO1 [60,61]. At LAPLACE, Université de Toulouse, a 3D PIC code is applied for modeling the plasma transport in RF driven negative ion sources [55].…”

Section: Particle In Cell Modelling Of Negative Ion Sources For Fusionmentioning

confidence: 99%

Review of particle-in-cell modeling for the extraction region of large negative hydrogen ion sources for fusion

Wünderlich

Mochalskyy

Montellano

et al. 2018

Review of Scientific Instruments

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Particle-in-cell (PIC) codes are used since the early 1960s for calculating self-consistently the motion of charged particles in plasmas, taking into account external electric and magnetic fields as well as the fields created by the particles itself. Due to the used very small time steps (in the order of the inverse plasma frequency) and mesh size, the computational requirements can be very high and they drastically increase with increasing plasma density and size of the calculation domain. Thus, usually small computational domains and/or reduced dimensionality are used. In the last years, the available central processing unit (CPU) power strongly increased. Together with a massive parallelization of the codes, it is now possible to describe in 3D the extraction of charged particles from a plasma, using calculation domains with an edge length of several centimeters, consisting of one extraction aperture, the plasma in direct vicinity of the aperture, and a part of the extraction system. Large negative hydrogen or deuterium ion sources are essential parts of the neutral beam injection (NBI) system in future fusion devices like the international fusion experiment ITER and the demonstration reactor (DEMO). For ITER NBI RF driven sources with a source area of 0.9 × 1.9 m and 1280 extraction apertures will be used. The extraction of negative ions is accompanied by the co-extraction of electrons which are deflected onto an electron dump. Typically, the maximum negative extracted ion current is limited by the amount and the temporal instability of the co-extracted electrons, especially for operation in deuterium. Different PIC codes are available for the extraction region of large driven negative ion sources for fusion. Additionally, some effort is ongoing in developing codes that describe in a simplified manner (coarser mesh or reduced dimensionality) the plasma of the whole ion source. The presentation first gives a brief overview of the current status of the ion source development for ITER NBI and of the PIC method. Different PIC codes for the extraction region are introduced as well as the coupling to codes describing the whole source (PIC codes or fluid codes). Presented and discussed are different physical and numerical aspects of applying PIC codes to negative hydrogen ion sources for fusion as well as selected code results. The main focus of future calculations will be the meniscus formation and identifying measures for reducing the co-extracted electrons, in particular for deuterium operation. The recent results of the 3D PIC code ONIX (calculation domain: one extraction aperture and its vicinity) for the ITER prototype source (1/8 size of the ITER NBI source) are presented.

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Development of a versatile multiaperture negative ion source

Cited by 26 publications

References 13 publications

A 2D Particle in Cell model for ion extraction and focusing in electrostatic accelerators

A 2D Particle in Cell model for ion extraction and focusing in electrostatic accelerators

Observation of beamlet displacement and parallelism in NIO1

Review of particle-in-cell modeling for the extraction region of large negative hydrogen ion sources for fusion

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