An RF beam Sweeper for Purifying In-Flight Produced Rare Isotope Beams

The Argonne Tandem Linac Accelerator System (ATLAS) is the only national user facility for low-energy stable heavy ion beams. Beams of radioactive nuclei produced by the in-flight method provide access to more than 100 short-lived isotopes. After traversing the production target, the primary beam is energy degraded and acquires a long low-intensity energy tail from the multiple-scattering processes in the target material. For low intensity rare isotope beams, these tails can easily dominate the total delivered beams. In response to this problem, RadiaBeam Systems has designed a cost-efficient DC/RF sweeper resonator, capable of producing a 150kV effective deflecting voltage. High efficiency is achieved by using the coils and electrodes design, optimized to reduce RF power losses and Class-E solid state amplifiers that can achieve up 85% efficiency. In Phase I, we performed the detailed RF design of this cavity, as well as conceptual engineering design, which included thermal and structural analysis, to ensure the stable operation. Primary subcomponents such as RF coupler, tuner, cooling and vacuum systems, DC and RF power supply have been considered. In Phase II, we will finalize the engineering design of the separator and verify its performance with computer analysis. After the cavity is fabricated, we will perform tuning and cold RF tests at RadiaBeam, then deliver the prototype to ANL, where it will be power tested and integrated into ATLAS for online beam tests. The results of this work will be of immediate benefit to the ATLAS facility. In addition, a similar separator could be used at FRIB for radioactive beam separation. RF sweepers are also of interest for mass- spectrometry as they can provide very precise isotope separation, which is critical for security, defense, and environmental applications.