Speaker
Description
A critical issue in the development of radio frequency (RF) negative ion sources for ITER neutral beam injection (NBI) is the large beam divergence angle. One of the potential causes is the deformation of the beam extraction interface (meniscus) induced by the RF electric field. Previous work showed that the applied RF electric field near the meniscus triggered both oscillations and an increase in the beam divergence [1]. In this study, we developed a beam focusing model accounting for the RF electric field at the meniscus and compared it with previous experimental results. In this model, the RF electric field was introduced as a perturbation to the meniscus. The linear response of the model reproduced the experimentally observed oscillations of the beam divergence. The non-linear response (an increase in the divergence angle) was also reproduced by the time-averaging effect of the oscillations. It was confirmed that the linear and non-linear responses of beam focusing can consistently be explained by the model.
| Email address | yasui.tsuyoshi@nifs.ac.jp |
|---|---|
| Funding Agency | JSPS KAKENHI Grant Number 25K00989 and NIFS Collaboration Research Program (NIFS23KIIR023). |
| Classification/Track | Beam formation / meniscus |
| Visitor's Visa | no |
| Classification | Beam formation and low energy transport |
| Footnote | [1] K. Nagaoka et al., Sci. Rep. 15, 1494 (2025). |