• Y. Higurashi, M.K. Fujimaki, A. Goto, E. Ikezawa, O. Kamigaito, M. Kase, M. Komiyama, T. Nakagawa, J. Ohnishi, Y. Watanabe
  RIKEN Nishina Center, Wako
• T. Aihara, M. Tamura, A. Uchiyama
  SHI Accelerator Service Ltd., Tokyo

The next generation heavy ion accelerator facility, such as the RIKEN RIBF, requires great variety of high charged heavy ions with a magnitude higher beam intensity than currently achievable. In the last decade, performance of the ECR ion sources has been dramatically improved with increasing the magnetic field and RF frequency to enhance the density and confinement time of plasma. Furthermore, the effects of the key components (magnetic field configuration, gas pressure etc) on the ECR plasma have been revealed. Such basic studies give us how to optimize the ion source structure. Based on these studies and the technology, we successfully constructed the new 28GHz SC-ECRIS which has a flexible magnetic field configuration to enlarge the ECR zone and to optimize the field gradient at ECR point. In the test experiment, we obtained the direct evidence that the field gradient and the zone size strongly affect the beam intensity. It concludes that the gentler field gradient and large ECR zone size gives intense beam of highly charged heavy ions from ECR plasma. In this contribution, we report the systematic study of these effects on the beam intensity of highly charged heavy ions.