Study of H&lt;sup&gt;−&lt;/sup&gt; Production in DC H&lt;sup&gt;−&lt;/sup&gt; Source of Medical Cyclotron

Etoh, H.; Onai, M.; Aoki, Yasushi; Mitsubori, H.; Arakawa, Y.; Sakuraba, J.; Kato, Takanori; Mitsumoto, T.; Yajima, S.; Shibata, T.; Hatayama, A.; Okumura, Y.

doi:10.1585/pfr.11.2406063

Cited by 6 publications

(11 citation statements)

References 23 publications

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“…As discussed below, the non-equilibrium features of the EEDF are very important for the both volume and surface H − production. [17,18,64,65] Here, we focus on the modeling of Cs-free H − VP. As mentioned in section 1, the H − VP is mainly through the following two step processes, (1) the production of vibrationally excited H 2 (v) molecules (EV process) by fast energetic electrons (E>20 eV), and (2) H − production (DA process) by slow electrons (E<1 eV).…”

Section: Modeling Of Multi-cusp Arc-discharge Sourcesmentioning

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: Modeling Of Multi-cusp Arc-discharge Sourcesmentioning

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 magnetic filter field is optimized so as to maximize the arc efficiency, defined as the ratio of the beam current to the arc power in Cs-free operation [2]. Effects of magnetic filter strength and arc power on H − production in Cs-free operation have also been studied by KEIO-MARC code [8,9]. There are two arch shaped tungsten filaments on the end flange to generate plasma via arc discharge between these filaments and the chamber wall.…”

Section: Apparatusmentioning

confidence: 99%

Development of a 20 mA negative hydrogen ion source for cyclotrons

Etoh

Onai

Arakawa

et al. 2017

AIP Conference Proceedings

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Effect due to plasma electrode adsorbates upon the negative ion current and electron current extracted from a negative ion source AIP Conference Proceedings 1869, 030025 (2017) Abstract. A cesiated DC negative ion source has been developed for proton cyclotrons in medical applications. A continuous H − beam of 23 mA was stably extracted at an arc power of 3 kW. The beam current gradually decreases with a constant arc power and without additional Cs injection and the decay rate was about 0.03 mA (0.14%) per hour. A feedback control system that automatically adjusts the arc power to stabilize the beam current is able to keep the beam current constant at ±0.04 mA (±0.2%).

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“…The geometrical model of the SHI source is shown in Fig. 1 [1]. The source consists of cylindrical chamber (100mm diameter and 160mm in length) made of copper, arch shaped filaments made of tungsten, cusp magnets, filter magnets, the plasma electrode, the extraction electrode and the grounded electrode.…”

Section: Keio-marc Codementioning

confidence: 99%

“…The number of electrons emitted from the filaments is determined by the arc-discharge current. The space inside the (1) 030043-2 plasma chamber is divided into small cubic cells (2mm 2mm 2mm) and the resultant EEDF is calculated in each cells.…”

Section: Keio-marc Codementioning

confidence: 99%

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Numerical modeling of the negative hydrogen ion production in the ion source for cyclotrons

Onai

Etoh

Mattei

et al. 2017

AIP Conference Proceedings

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Abstract.A filament driven multi-cusp negative ion source has been developed for proton cyclotron applications. In this study, numerical analysis of the volume production in the negative ion source has been conducted by the KEIO-MARC code and zero dimensional rate equations. The code calculate the Electron Energy Distribution Function (EEDF) in multi-cusp arc discharge sources from the following main input parameters: 1) 3D geometry of the source chamber and filaments, 2) 3D magnetic configuration, 3) arc voltage, 4) arc current and 5) gas pressure. Using the EEDF, we can also estimate the resultant amount of the H-volume production by the 0D rate equations. In this paper, we focus on the dependency of the production on the filter magnetic field and the arc-discharge voltage. It is shown that KEIO-MARC code reproduces the magnetic filter effect, i.e., the electron temperature and density are reduced across the filter region. Also, the 0D analysis shows that the amount of H-production increases with the arc-voltage, but is gradually saturated in the high voltage region ( >150V . The mechanism which leads to the saturation is possibly explained by the saturation of the electron density in such a high voltage regime.

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Study of H<sup>−</sup> Production in DC H<sup>−</sup> Source of Medical Cyclotron

Cited by 6 publications

References 23 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

Development of a 20 mA negative hydrogen ion source for cyclotrons

Numerical modeling of the negative hydrogen ion production in the ion source for cyclotrons

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