Production of high intensity high charge state uranium ion beams in afterglow mode with advanced electron cyclotron resonance (ECR) ion sources.

To satisfy the requirement of heavy ion synchrotron for intense highly charged ion beams, a comprehensive study of the afterglow mode was performed with two advanced electron cyclotron resonance (ECR) ion sources, i.e., a second-generation ECR ion source (LECR4) and a third-generation ECR ion source (SECRAL-II). Intense pulsed uranium ion beams of highly charged states were produced with both ion sources (e.g., 58 eμA of 238U39+ in LECR4 and 124 eμA of 238U46+ in SECRAL-II). Compared to the beam intensity records obtained in continuous wave mode, the gain factor is up to ∼6. It was found that the optimum microwave pulse width and the decay time in SECRAL-II operating at 24 GHz are obviously longer than those in LECR4 operating at 14.5 GHz, aligning with a previous observation made with SECRAL-II ion source.