Efficient Fragment Separator for High Energy Secondary Radioactive Beams

Technical Report · Mon May 25 00:00:00 EDT 2020

OSTI ID:1630648

Kutsaev, Sergey

Radioactive beams have a major impact on studies of nuclear structure and nuclear physics far from stability. One of the important challenges facing nuclear physics is to describe neutron- and proton-rich isotopes that approach the edge of stability. The Facility for Rare Isotope Beams (FRIB) will be a cuttingedge research facility to enable scientists to make discoveries about the properties of rare isotopes in order to better understand the physics of nuclei, nuclear astrophysics, fundamental interactions, and applications for society. During the projectile fragmentation isotope production, along with the desired rare isotope, up to 1000 other isotopes are produced that could be harvested and used for other experiments or applications in a commensal mode of operation. To maximize the FRIB scientific program, the secondary fragments must be filtered to ensure the delivery of rare isotopes with high rates and high purities. The key part of the FRIB facility will be a next-generation three-stage magnetic projectile fragment separator specifically designed to handle the very intense primary and secondary beams. However, in magnetic fragment separator, the contaminant isotopes are still found at lower magnetic rigidity than their more stable counterparts. Thus, another criterion is needed to further purify the radioactive beam, i.e. by using a velocity filtering device. In response to this problem, RadiaBeam Systems in collaboration with FRIB scientists have designed an RF separator capable of producing a 300 kV kick with 18 cm aperture that can realize such velocity selection technique. A time difference eventually develops between the fragments due to the velocity difference. The fragments then arrive to different phases of the deflecting RF field in the kicker. Out-of-phase fragments are deflected from the beam axis and then removed by the slit. In Phase I of this project we have explored different candidates for accelerating structures of the separator, including split-coaxial resonator (SCR), single- and double- quarter-wave resonator (QWR) and Hresonators (IH- and CH-) and selected DQWR as the most applicable for fabrication and operations. We have, then, performed a detailed electromagnetic design and optimization to reduce RF power requirements and losses, and ensure the stable operational parameters (such as peak E- field). We have ensured via beam dynamics simulations that the beam is deflected by 13 mm after going through the cavity per FRIB requirements. The conceptual engineering design, which includes vacuum chamber, RF cavities, electrodes, couplers, tuners and cooling system was designed afterwards. We have done structural, thermal and CFD analysis to ensure the stable operation. In addition, we have designed an efficient RF power source based on solid-state technology and tested a single module.

• Research Organization: RadiaBeam Technologies, Santa Monica, CA (United States)
• Sponsoring Organization: USDOE Office of Science (SC)
• DOE Contract Number: SC0019723
• OSTI ID: 1630648
• Type / Phase: SBIR (Phase I)
• Report Number(s): DOE-RBS-19723
• Country of Publication: United States
• Language: English