Modeling of plasma transport and negative ion extraction in a magnetized radio-frequency plasma source

Fubiani, G.; Garrigues, Laurent; Hagelaar, Gerjan; Kohen, Nicolas; Boeuf, Jean-Pierre

doi:10.1088/1367-2630/19/1/015002

Cited by 68 publications

(95 citation statements)

References 72 publications

(121 reference statements)

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“…The symbols j and k denote particle species. Recently, almost the same 2D3V ES-PIC modelings [32,43], but with the different scaling (i.e., reduced-density scaling) have been done with a more detailed model of the collision processes with Monte-Carlo method for collisions (MCC).…”

Section: Introductionmentioning

confidence: 99%

Present status of numerical modeling of hydrogen negative ion source plasmas and its comparison with experiments: Japanese activities and their collaboration with experimental groups

et al. 2018

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The present status of kinetic modeling of particle dynamics in hydrogen negative ion (H − ) source plasmas and their comparisons with experiments are reviewed and discussed with some new results. The main focus is placed on the following topics, which are important for the research and development of H − sources for intense and high-quality H − ion beams: (i) effects of non-equilibrium features of electron energy distribution function on volume and surface H − production, (ii) the origin of the spatial non-uniformity in giant multi-cusp arc-discharge H − sources, (iii) capacitive to inductive (E to H) mode transition in radio frequency-inductively coupled plasma H − sources and (iv) extraction physics of H − ions and beam optics, especially the present understanding of the meniscus formation in strongly electronegative plasmas (so-called ion-ion plasmas) and its effect on beam optics. For these topics, mainly Japanese modeling activities, and their domestic and international collaborations with experimental studies, are introduced with some examples showing how models have been improved and to what extent the modeling studies can presently contribute to improving the source performance. Close collaboration between experimental and modeling activities is indispensable for the validation/improvement of the modeling and its contribution to the source design/development. chamber wall (anode) and filaments (cathode). In the latter sources, the RF-electromagnetic field is used to generate and heat plasmas.In this review, we mainly focus on the modeling studies, especially the modeling study of H − source plasmas using kinetic approaches, such as the test particle Monte-Carlo model [14] and particle in cell (PIC) model [14,15], which has been reviewed in [16]. Here, we extend it with some new results. Close collaboration between the experimental and modeling study is very important as it can improve our basic understanding of source plasmas. Various examples of the model validation will be shown through comparisons with experiments and also how modeling studies contribute to the improvement of source performances.As for the multi-cusp arc-discharge source, we will first show a systematic study to help us understand the role of the EEDF on the H − VP in section 2.2. The study has been carried out for a compact multi-cusp arcdischarge source (SHI H − source: Sumitomo Heavy Industry H − source [17,18]) for medical application such as boron neutron capture therapy and the radioisotope production for molecular imaging technology.The SHI H − source is a typical tandem type H − source [19]. In such a tandem type volume sources, the plasma source volume is divided into two regions by the transverse magnetic field (the so-called magnetic filter filed: MF-field) to control the EEDFs and to promote the two step H − VP reactions explained above. Namely, the source volume consists of two regions: (1) the 'driver region' where the electron energy is high and the EV process is promoted, and (2) the 'extraction region' where the electr...

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Section: Introductionmentioning

confidence: 99%

Present status of numerical modeling of hydrogen negative ion source plasmas and its comparison with experiments: Japanese activities and their collaboration with experimental groups

et al. 2018

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“…The negative space charge in front of electrically biased grids in a negative ion source is important because it can adversely affect the extraction of negative ions from the plasma. The sheath width obtained in the present study can be useful for choosing the appropriate grid size and the number of simulating particles in 2D/3D PIC with Monte Carlo collision simulation techniques used for optimized computing in negative ion sources . An important result from this study indicates that the sheath width increases during negative ion emission from the electrode surface.…”

Section: Discussionmentioning

confidence: 66%

“…The sheath width obtained in the present study can be useful for choosing the appropriate grid size and the number of simulating particles in 2D/3D PIC with Monte Carlo collision simulation techniques used for optimized computing in negative ion sources. [70] An important result from this study indicates that the sheath width increases during negative ion emission from the electrode surface. As a result, the positive ion transit time inside the sheath will increase; therefore, the probability of interaction with the background ions/neutrals should also increase.…”

Section: Discussionmentioning

confidence: 72%

Positive ion speed at the plasma–sheath boundary of a negative ion‐emitting electrode

Pandey

Karkari

2020

Contributions to Plasma Physics

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One‐dimensional fluid model for a planar sheath in front of a negative ion‐emitting electrode surface immersed in a collision‐less, non‐magnetized, electronegative plasma is presented. It was found that the positive ion speed at the plasma–sheath boundary (PSB) increases linearly with negative ion emission from the electrode but attains a saturation value as soon as a virtual cathode is formed near the electrode surface. The effect of negative ion emission on the pre‐sheath region shows that the potential drop increases across the pre‐sheath in accordance with the rise in positive ion speed at the PSB. The sheath width obtained using the present model shows a similar trend as the Child‐Langmuir law, but its magnitude is found to be consistently higher compared with a non‐emitting electrode. A plausible explanation has been given to explain these effects.

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“…This reveals asymmetries resulting from electron drifts and provides insight into the complexity of the plasma expansion chamber. Fubiani presents a similar approach focusing on meniscus interaction involving high plasma density physics, transport of neutrals and chemistry on low work functions surfaces [30].…”

Section: Negative Ion Source Beam Intensities Across 20 Orders Of Magmentioning

confidence: 99%

Focus on sources of negatively charged ions

Fantz

Lettry

2018

New J. Phys.

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This focus issue presents theoretical investigations, modelling and technical achievements across the large variety of sources of negatively charged ions (NCI). The twenty contributions cover a fraction of the very broad range of applications requiring very different time structure, intensities and beam energies. The world's largest NCI source area is 1×2 m 2 and shall provide 1280 beamlets of ∼30 mA intensity each, while the smallest unit of our selection is only a few mm 2 and requires the highest ionization efficiencies to deliver negative radioisotope-ions far from stability produced via nuclear reactions at rates down to or below few atoms per seconds.

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Modeling of plasma transport and negative ion extraction in a magnetized radio-frequency plasma source

Cited by 68 publications

References 72 publications

Present status of numerical modeling of hydrogen negative ion source plasmas and its comparison with experiments: Japanese activities and their collaboration with experimental groups

Present status of numerical modeling of hydrogen negative ion source plasmas and its comparison with experiments: Japanese activities and their collaboration with experimental groups

Positive ion speed at the plasma–sheath boundary of a negative ion‐emitting electrode

Focus on sources of negatively charged ions

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