Variable wedge for ARIS

At the Facility for Rare Isotope Beams (FRIB) Advanced Rare Isotope Separator (ARIS), wedges filter rare isotopes and produce beams of specified isotopes for experiments. Proper wedges (with the right thickness, angle, and density variation) efficiently collect and purify rare isotope beams by selectively slowing desired beams and contaminants via atomic interactions while maintaining achromaticity. Currently, wedges are designed, fabricated, and swapped for each experiment based on LISE++ analysis. While effective, this process requires significant preparation time, and the single-wedge operation allows no adjustments for calculation, material, or fabrication errors. To enhance ARIS, a variable wedge system is being developed. It consists of four degraders: two with quadratic cross sections forming an angle-tunable wedge and two linear-shaped pieces adjusting thickness. By modifying their positions, the system achieves angle variation of 1–20 mrad and thickness variation of 0.5–20 mm. This paper presents the system’s principle, design, performance estimation, and simulation results, demonstrating improved efficiency, higher isotope yield, and reduced FRIB operation costs.