Speaker
Description
Negative hydrogen (H$^{-}$) ion production on cesiated metal surfaces is a key process for high-intensity H$^{-}$ ion sources for neutral beam injection systems. Electron transfer from a low-work-function surface to an incident hydrogen atom produces H$^{-}$ ions$^{*}$ near an extraction hole. Semi-continuous Cs supply maintains the low-work-function of the plasma grid (PG)$^{**}$, while intense atomic hydrogen flux on the PG destroys H$^{-}$ ions by associative detachment and can modify the surface atomic structure and near-surface loss processes. The relation between atomic hydrogen flux and H$^{-}$ ion current remains unanswered because positive ions and electrons coexist near the PG surface.
We are experimentally investigating H$^{-}$ ion surface production using an ECR atomic hydrogen source originally developed for biomolecular mass analysis$^{***}$. A Cs-deposited metal target plate simulates the PG, and the H$^{-}$ ion current extracted through the target is measured as a function of atom-source parameters including power, H$_{2}$ flow rate, and duty factor. A Faraday-cup system has shown a clear time-of-flight signal of charged particle flux, and an H$^{-}$ ion detection system with an electron suppressor is being assembled.
| Email address | cygn0002@mail4.doshisha.ac.jp |
|---|---|
| Funding Agency | JSPS KAKENHI Grant Number 23K25855 |
| Classification/Track | Main: Caesium management, Sub: Fundamental processes and modeling |
| Visitor's Visa | no |
| Classification | Caesium management |
| Footnote | * C. Wimmer et al., Fusion Eng Des, 215, 114949 (2025) ** M. Bacal and M. Wada, Appl. Phys. Rev., 2(2), 021305, (2015) *** H. Takahashi et al., Anal. Chem., 88(7), 3810–3816, (2016) |