Speakers
Description
At the Facility for Rare Isotope Beams (FRIB), the Advanced Rare Isotope Separator (ARIS)* uses wedge degraders to purify rare isotope beams for experiments. Currently, custom aluminum wedges must be designed and fabricated for each experiment, allowing no adjustment for online optimization or fabrication errors, which limits tuning efficiency.
To address these limitations, a variable wedge system is being developed to achieve 1–20 mrad angle variation and 0.5–20 mm total thickness adjustment, using aluminum as the reference case. Note that the achievable ranges vary with the density of the wedge material. Two design approaches are under study.
The six-piece variable wedge includes two pairs of quadratic-profile aluminum wedges** for large and small angle ranges to improve angular precision, and two linear pieces for fine thickness control. An optimization algorithm determines relative displacements for target conditions. The system has advanced from theoretical simulation to a physical prototype, validating motion control and mechanical feasibility for potential beamline use.
The liquid wedge features a sealed fluid-filled chamber with windows driven by stepper-based linear actuators, enabling adjustment of tilt and axial positions based on target inputs. Detailed mechanical modeling and Geant4 simulations confirm feasibility.
Both systems demonstrate promising functionality and tunability to improve isotope purity and beam delivery for future FRIB experiments.
Footnotes
- M. Hausmann, A.M. Aaron, A.M. Amthor, et al., "Design of the Advanced Rare Isotope Separator ARIS at FRIB," Nucl. Instrum. Methods Phys. Res. B, Vol. 317, Part B, 2013, pp. 349-353, ISSN 0168-583X.
** J. Hwang, S. Michimasa, S. Ota, et al., "Angle-tunable wedge degrader for an energy-degrading RI beamline," PTEP 2019 (2019) 4, 043D02, DOI: 10.1093/ptep/ptz028.
Funding Agency
U.S. Department of Energy, Office of Science, Office of Nuclear Physics, under Award No. DE-SC0023633, and Facility for Rare Isotope Beams (FRIB).
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