Recent development of RIKEN 28 GHz superconducting electron cyclotron resonance ion source

Over the past two years, we have tried to improve the performance of the RIKEN superconducting electron cyclotron resonance ion source using several methods. For the production of U vapor, we chose the sputtering method because it is possible to install a large amount of material inside the plasma chamber and thus achieve long-term operation without a break, although it is assumed that the beam intensity is weaker than in the oven technique. We also used an aluminum chamber instead of a stainless steel one. Using these methods, we successfully produced ∼180 eμA of U(35+) and ∼230 eμA of U(33+) at the injected radio frequency (RF) power of ∼4 kW (28 GHz). Very recently, to further increase the beam intensity of U(35+), we have started to develop a high temperature oven and have successfully produced a highly charged U ion beam. In this contribution, we report on the beam intensity of highly charged U ions as a function of various parameters (RF power and sputtering voltage) and discuss the effects of these parameters on the beam stability in detail.