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TY - UNPB AU - Nakagawa, T. AU - Higurashi, Y. AU - Ohnishi, J. TI - Further Improvement of Performance of RIKEN 28GHz SC-ECRIS and Search for the Optimum Structure of ECR Ion Sources J2 - Proc. of Heavy Ion Accelerator Technology Conference (HIAT2015), Yokohama, Japan, 7-11 September 2015 AB - To search for the optimum structure of the ECR ion source, we studied the effect of the main parameters (magnetic field, etc) of RIKEN SC-ECRIS on the beam intensity for various heavy ions (Ar~U) with 18 and 28GHz. In the systematic studies, we observed that the beam intensity is strongly dependent on these parameters. For examples, optimum value of Bmin for maximizing the beam intensity was dependent on the microwave frequency (~0.8Becr (18GHz), 0.6~0.65Becr (28GHz)) and gas pressure. We found that the optimum value of Br to maximize then beam intensity is strongly dependent on Bmin in a certain condition. Based on these studies, even though we used the magnetic field lower than the ordinary "High-B mode", we obtained more than 200euA of U³⁵⁺ at lower RF power. We could dramatically reduce the consumption rate of metal U form ~8.6 to ~2.8mg/h to produce 150euA of U³⁵⁺. In this contribution, we present the effect of main parameters on the beam intensities for various heavy ions and mechanisms in detail. We show how to optimize the performance to obtain the intense U beam. Based on these studies, we also describe the optimum structure for higher microwave frequency. PB - JACoW CY - Geneva, Switzerland ER -