RECENT DEVELOPMENTS IN RIKEN 28-GHZ SC-ECRIS

We improved the performance of the RIKEN 28GHz SC-ECRIS with several methods. For production of the U vapor, we chose the sputtering method. Using sputtering method, it is possible to install the large amount of material in the plasma chamber for achieving the long term operation without break. We also used the Al chamber instead of stainless steel one. Using these methods, we successfully produced ~185eA of U, ~230eA of U at the injected RF power of 2~3kW (28GHz). We observed that the beam intensity and stability are strongly dependent on the sputtering voltage, material position, biased disc voltage and its position. We continuously produced intense U ion beam for Riken RIBF experiment longer than one month without break. In this contribution, we will report the beam intensity of highly charged U ions as a function of various parameters (RF power, sputtering voltage etc.) We also present the experience of the long term operation of the ion source for the RIKEN RIBF experiments.