Beam commissioning of the RAON injector and low-energy superconducting linac SCL3

Abstract

Beam commissioning of the RAON linac has been carried out with various ion species in the injector and with ⁴⁰Ar⁹⁺ and ⁴⁰Ar⁸⁺ beams in the low-energy superconducting linac SCL3. This paper primarily reports the results obtained with ⁴⁰Ar⁸⁺ beams, while data from other ion species are included when needed. A beam-tuning procedure for the LEBT based on Allison scanner data was established, enabling proper beam matching at the RFQ entrance. In the MEBT, transverse beam parameters were refined through wire-scanner measurements. During SCL3 beam commissioning, cavity settings obtained from phase scans yielded beam energies consistent with TRACK predictions and were confirmed by TOF measurements. The SCL3 transmission was lower than expected, indicating that further study is required to clarify and mitigate the beam-loss mechanisms, including possible limitations in the longitudinal acceptance.