Experimental Demonstration of the Thin-Film Liquid-Metal Jet as a Charge Stripper

For high-power heavy ion accelerators, the development of a suitable charge stripper, which can handle intense beams, is essential. This Letter describes the first experimental demonstration of a heavy ion liquid lithium charge stripper. A $10–20\mu \mathrm{m}$ thick liquid lithium jet flowing at $>50\mathrm{m}/\mathrm{s}$ was formed and confirmed stable when bombarded by various heavy ion beams, while increasing the charge state of the incoming beams to the desired charge state range. This demonstration proved the existing power limitation with the conventional strippers can be overcome by the liquid-metal stripper, opening completely new possibilities in high-power accelerator development.

Figure 1

Schematic of liquid lithium charge stripper system and lithium film. (a) Schematic illustration of the LLCS system, area indicated by red-dot line with more details shown in (b) and (c). (b) Photograph of the liquid lithium film formed in the LLCS vacuum chamber. The extremely smooth surface of the lithium film appeared as a mirror. (c) Illustration of the liquid lithium film with labels for clarity.

Figure 2

Spatial profile of the liquid lithium film obtained from the energy loss measurement with $20\mathrm{MeV}/u$ Ar beam. (a) A two-dimensional profile. Red circle indicates a typical beam location of a 1 mm beam relative to the film. Dashed lines indicate where cross sectional profiles were obtained, which are shown in (b) and (c). (b) Vertical cross sectional thickness profile. (c) Horizontal cross sectional thickness profile.

Figure 3

Xenon (red) and uranium (blue) charge state distributions after the liquid lithium stripper. The thickness is $1.05\mathrm{mg}/{\mathrm{cm}}^2$ for the xenon and $1.40\mathrm{mg}/{\mathrm{cm}}^2$ for uranium beams.