Speaker
Description
Caesium-free negative ion sources have been actively studied to reduce vacuum contamination and improve maintainability. Such demands are increasing beyond neutral beam injection systems, including accelerator mass spectrometry (AMS). In AMS, 2 m × 2 m scale $^{14}$C systems for wider use are being developed $^{1)}$, increasing interest in safer caesium-free operation compared with conventional caesium sputter sources.
One possible approach is surface negative ion generation using low-work-function (low-φ) materials. A major issue is surface contamination with adsorbates, which increases the work function and reduces ion production efficiency. The author has investigated microwave heating of granular low-φ materials as a possible solution.$^{2)}$ Since microwave heating of conductive materials is mainly limited to the skin-depth region, the use of granules can increase the heated area contributing to negative ion production.
Proof-of-concept experiments using LaB$_6$ granules and methane gas confirmed production of carbon molecular negative ions.$^{2)}$ However, experiments using CO$_2$ revealed carburization and oxidation of the LaB$_6$ surface, suggesting that surface reactions may become an important issue under CO$_2$ atmospheres. Based on these results, we are extending this low-φ material approach toward helium negative ion generation for industrial applications.
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$ ^{1)}$ S. Jinno, A. Matsubara, N. Fujita, K. Kimura, Nucl. Instr. and Meth. B 557, 165545 (2024).
$^{2)}$ A. Matsubara, Y. Kokubu, K. Nishio, K. Kimura, K. Kashimura, K. Shimada, N. Fujita, Nucl. Instr. and Meth. B 568, 165863 (2025).
| Email address | matsubara.akihiro@pesco.co.jp |
|---|---|
| Visitor's Visa | no |
| Classification | Applications of Negative sources - medical (diagnostics, therapy), industrial (implantation, materials analysis, carbon dating, discovery science |