Challenge
RAON (Rare isotope Accelerator complex for ON-line experiments), Korea’s first heavy-ion accelerator, requires a charge stripper to increase uranium beam charge state from 34+ to 79+ for achieving 200 MeV/u energy. This requires forming a precise 22 μm thick liquid lithium film. However, existing electromagnetic thrusters weighing 340 kg make maintenance extremely difficult.
Approach: Lightweight Helical EM Thruster
Fig. Design evolution: conventional EM thruster (left) vs redesigned lightweight thruster (right)
Electromagnetic Thruster Optimization
- Helical-type MHD design with Sm₂Co₁₇ permanent magnets
- Single-direction magnet arrangement for weight reduction
- SUS316 construction for lithium compatibility
- FEM simulation using COMSOL and ANSYS Maxwell
Charge Stripper System
- Nozzle optimization: 0.7 mm diameter, 34° angle
- Laser thickness measurement (replacing electron gun method)
- Curved deflector design to minimize lithium droplet contamination
Results
Fig. Experimental test loop system (left) and successfully formed liquid lithium thin film (right)
| Parameter | Conventional | Redesigned |
|---|---|---|
| Weight | 340 kg | 21 kg (-94%) |
| Input Current | 872 A | 500 A (-43%) |
| Developed Pressure | 10.5 bar | 14.6 bar (+40%) |
- Achieved 22 μm lithium film thickness at 107 A input current
- 94% weight reduction enabling easy maintenance
- Laser-based thickness measurement avoids the electron-beam measurement method
- Verified the film thickness required for a 79+ uranium charge state; beam charge-state conversion was not measured in this study
Publication
SCIE
- T.U. Kang, G. Lee, H.R. Kim, “Experimental characterization of the flowline of a lithium film formed using an electromagnetic thruster for a RAON prototype charge stripper,” Nuclear Engineering and Design, 412, 112481, 2023. DOI
Research Project
(2020-2021) Research on the development of prototype lithium charge stripper, Institute for Basic Science.