Speaker
Description
Beam oscillation has been observed in radio-frequency negative hydrogen ion sources (e.g., Ref. [1]). Recently, the oscillation has been investigated using an electrostatic Particle-in-Cell (PIC) simulation, and the behavior resulted from oscillations in the source plasma density [2]. In the simulation, it was assumed that the source plasma in the driver region periodically oscillates, while the surface production rate of the negative ions remains constant. To further understand the mechanism of beam oscillation, this research focuses on plasma kinetics, particularly the fluxes onto the plasma grid (PG), using the electromagnetic PIC Monte Carlo collision code NINJA [3], which incorporates a neutral transport module. The results indicate that the spatially averaged atomic hydrogen flux onto the PG exhibits no periodic oscillation. This suggests that the number of surface-produced negative hydrogen ions per unit time, which are derived from atomic hydrogen, is stable and does not cause the beam oscillation. The presentation will also discuss the behavior of the generated plasma and its influence on the extraction region, including magnetic field and particle energy distributions.
| Email address | n.kawamura@keio.jp |
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| Visitor's Visa | no |
| Classification | Numerical simulations of sources, beams, space-charge, ion-optics |
| Footnote | [1] T. Shibata et al., AIP Conf. Proc. 2373, 050002 (2021). [2] K. Hayashi et al., 21st International Conference on Ion Sources, Oxford, UK, September 2025. [3] S. Mattei et al., J. Comput. Phys. 350, 891 (2017). |