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Journal Articles

Study of negative hydrogen ion beam optics using the 2D PIC method

Miyamoto, Kenji*; Okuda, Shin*; Hatayama, Akiyoshi*; Hanada, Masaya; Kojima, Atsushi

AIP Conference Proceedings 1515, p.22 - 30, 2013/02

 Times Cited Count:10 Percentile:94.94

We have developed the integrated 2D PIC code for the analysis of the negative ion beam optics, in which an overall region from the source plasma to the accelerator is modeled. Thus, the negative ion trajectory can be solved self-consistently without any assumption of the plasma meniscus form initially. This code can reproduce the negative ion beam halo observed in an actual negative ion beam. It is confirmed that the surface produced negative ions which are extracted near the edge of the meniscus can be one of the reasons for the beam halo: these negative ions are over-focused due to the curvature of the meniscus. The negative ions are not focused by the electrostatic lens, and consequently become the beam halo.

Journal Articles

Study of plasma meniscus formation and beam halo in negative hydrogen ion sources

Okuda, Shin*; Miyamoto, Kenji*; Fukuyama, Toshishige*; Nishioka, Shu*; Hatayama, Akiyoshi*; Fukano, Azusa*; Hanada, Masaya; Kojima, Atsushi

AIP Conference Proceedings 1515, p.107 - 113, 2013/02

 Times Cited Count:9 Percentile:94.02

A meniscus of plasma-beam boundary in H$$^{-}$$ ion sources largely affects the extracted H$$^{-}$$ ion beam optics. Recently it is shown that the beam halo is mainly caused by the meniscus, i.e. ion emissive surface, close to the plasma grid (PG) where its curvature is large. The purpose of this study is to clarify the effect of H$$^{-}$$ surface production rate on plasma meniscus and beam halo formation with PIC (particle-in-cell) modeling. It is shown that the plasma meniscus and beam halo formation is strongly dependent on the amount of surface produced H$$^{-}$$ ions.

Journal Articles

Study of beam optics and beam halo by integrated modeling of negative ion beams from plasma meniscus formation to beam acceleration

Miyamoto, Kenji*; Okuda, Shin*; Hatayama, Akiyoshi*; Hanada, Masaya; Kojima, Atsushi

Applied Physics Letters, 102(2), p.023512_1 - 023512_4, 2013/01

 Times Cited Count:24 Percentile:69.14(Physics, Applied)

To understand the physical mechanism of the beam halo formation in negative ion beams, a two-dimensional particle-in-cell code for simulating the trajectories of negative ions created via surface production has been developed. The simulation code reproduces a beam halo observed in an actual negative ion beam. The negative ions extracted from the periphery of the plasma meniscus (an electro-static lens in a source plasma) are over-focused in the extractor due to large curvature of the meniscus.

Journal Articles

Numerical analysis of surface produced H$$^{-}$$ ions by using two-dimensional particle-in-cell method

Miyamoto, Kenji*; Okuda, Shin*; Hatayama, Akiyoshi*; Hanada, Masaya

Review of Scientific Instruments, 83(2), p.02A723_1 - 02A723_4, 2012/02

 Times Cited Count:8 Percentile:37.74(Instruments & Instrumentation)

The modeling and analysis of a negative ion source is proceeding by using a 2D particle-in-cell simulation. The effect of the H$$^{-}$$ ion production on the plasma grid (PG) surface is investigated. It is shown that with the increase of H$$^{-}$$ ions per time step, the H$$^{-}$$ ion current density is enhanced, while the electron current density decreases with increasing the H$$^{-}$$ production rate on the PG surface. Theseresults agree well with the experimental results observed in typical negative ion sources. Moreover, it is found that plasma quasi-neutrality is held mainly by both H$$^{+}$$ and H$$^{-}$$ ions in the bulk plasma.

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