Speaker
Description
Tandem accelerators require negative helium He- ions for efficient two-stage acceleration. Currently, He- is produced via charge exchange in alkali metal vapor [1]. This method causes severe issues: downstream contamination, disastrous for semiconductor applications, high-voltage sparking, and hazardous maintenance [2]. We propose transitioning to an alkali-free, volume production method directly within a pure helium plasma. This requires resonant low-energy electron attachment to form He- and it usually involves the metastable He*($1s2s \ , ^3S$ ) state as intermediate step and/or end product for its auto-detachment.
To evaluate potential pathways, we outline a computational framework for the necessary atomic precursor cross-sections. Using R-Matrix or Close-Coupling methods [3], we compute energy-dependent cross-sections for metastable excitation, attachment, and destructive loss channels. Integrating these over the plasma Electron Energy Distribution Function (EEDF) yields macroscopic rate coefficients. These, fed into a 0D global plasma model, can help identify the optimal parameter space that maximizes He- yield, guiding the development of new He- implantation devices.
| Email address | shubhamsinghbaghel25@gmail.com |
|---|---|
| Visitor's Visa | no |
| Classification | Other negative ion sources for fusion, accelerators, and other applications |
| Footnote | References: • [1] Heinemeier, J., & Tykesson, P. (1977). Production of $\text{He}^-$ beams by charge exchange in alkali metal vapors. Review of Scientific Instruments, 48(11), 1486-1489. • [2] Bacal, M., & Wada, M. (2020). Negative ion sources. Applied Physics Reviews, 7(2), 021305. • [3] Bray, I., Fursa, D. V., Kadyrov, A. S., Stelbovics, A. T., Khakoo, M. A., & Kingston, A. E. (2002). Electron-and photon-helium scattering. Physics Reports, 358(3-4), 203-345. |