Analysis of the double-ion plasma in the extraction region in hydrogen negative ion sources

Fukuyama, Takashi; Okuda, S.; Fukano, Azusa; Tsumori, K.; Nakano, H.; Hatayama, A.

doi:10.1063/1.4792772

Cited by 8 publications

(14 citation statements)

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“…In various Cs-seeded negative ion sources, an 'ion-ion plasma' layer which mainly consists of positive and negative ions has been observed in front of the PG [51,52,98,99]. Especially, recent experiments on the ion-ion plasma in [51] triggered a series of 2D ES-PIC modeling studies [39][40][41][42] in order to find the answer for the questions: (i) 'why such a thick ion-ion plasma layer is produced under the H − SP? ', and 'from where H − ions are extracted?…”

Section: Extraction Physicsmentioning

confidence: 99%

“…A series of 2D3V ES-PIC (two-dimensional in real space and three-dimensional velocity space, ES-PIC) modeling has been done in [36][37][38][39][40][41][42]. A reduced-size-scaling has been adopted to save the computational cost by keeping important normalized parameters the same as those in the real system [36,[38][39][40][41][42], e.g., normalized Larmor radius r L, j Lj * r = / collisionality parameter L, jk jk * l l = / where L is the characteristic scale length of the real system, while r Lj and jk l are the Larmor radius and collision mean free path, respectively. The symbols j and k denote particle species.…”

Section: Introductionmentioning

confidence: 99%

“…The simple ES-PIC model in [36][37][38][39][40][41][42] mentioned above has been improved step-by-step through the model validation by comparisons with various experiments and other theoretical/numerical results [44][45][46]. The models give useful insights into the H − extraction process, and also help identify basic and intrinsic mechanisms of various interesting phenomena in the qualitative manner.…”

Section: Introductionmentioning

confidence: 99%

“…Modeling studies in [36][37][38][39][40][41][42] give useful insights in helping to solve these questions, but problems (4) and (5) above have not yet been completely understood. Understanding of the ion-ion plasma and also plasma meniscus (H − emitting surface) shape in such ion-ion plasma are very important in helping to obtain good beam optics and to reduce the beam halo component.…”

Section: Introductionmentioning

confidence: 99%

“…Recently, the 2D ES-PIC model in [36][37][38][39][40][41][42] above has been extended to the 3D ES-PIC model and simulations of the ion-ion plasma have been carried out [56]. The 2D ES-PIC results of the formation mechanism of the ion-ion plasma have been validated by the 3D ES-PIC model.…”

Section: Introductionmentioning

confidence: 99%

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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: Extraction Physicsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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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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Kinetic modeling of particle dynamics in H− negative ion sources (invited)

Hatayama

Shibata

Nishioka

et al. 2014

Review of Scientific Instruments

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Progress in the kinetic modeling of particle dynamics in H(-) negative ion source plasmas and their comparisons with experiments are reviewed, and discussed with some new results. Main focus is placed on the following two topics, which are important for the research and development of large negative ion sources and high power H(-) ion beams: (i) Effects of non-equilibrium features of EEDF (electron energy distribution function) on H(-) production, and (ii) extraction physics of H(-) ions and beam optics.

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Study of ion-ion plasma formation in negative ion sources by a three-dimensional in real space and three-dimensional in velocity space particle in cell model

Nishioka

Goto

Miyamoto

et al. 2016

Journal of Applied Physics

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Recently, in large-scale hydrogen negative ion sources, the experimental results have shown that ion-ion plasma is formed in the vicinity of the extraction hole under the surface negative ion production case. The purpose of this paper is to clarify the mechanism of the ion-ion plasma formation by our three dimensional particle-in-cell simulation. In the present model, the electron loss along the magnetic filter field is taken into account by the “τ///τ⊥ model.” The simulation results show that the ion-ion plasma formation is due to the electron loss along the magnetic filter field. Moreover, the potential profile for the ion-ion plasma case has been looked into carefully in order to discuss the ion-ion plasma formation. Our present results show that the potential drop of the virtual cathode in front of the plasma grid is large when the ion-ion plasma is formed. This tendency has been explained by a relationship between the virtual cathode depth and the net particle flux density at the virtual cathode.

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Analysis of the double-ion plasma in the extraction region in hydrogen negative ion sources

Cited by 8 publications

References 0 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

Kinetic modeling of particle dynamics in H− negative ion sources (invited)

Study of ion-ion plasma formation in negative ion sources by a three-dimensional in real space and three-dimensional in velocity space particle in cell model

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