Author: Nakagawa, T.
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TUA1 Development of Riken 28 GHz SC-ECRIS for Production of Intense Metal Ion Beam 44
 
  • T. Nakagawa, Y. Higurashi, T. Nagatomo, J. Ohnishi
    RIKEN Nishina Center, Wako, Japan
 
  To produce intense metal ion beams (e.g. Ti13+, V12+,13+, U35+ ) for super heavy element search and RIBF experiments at RIKEN, we tried to optimize the RIKEN 28 GHz SC-ECRIS performance. Based on the scaling low and 'high B mode' operation, we systematically measured the beam intensity of various heavy ions as a function of Binj, Br and Bext with 28 and 18 GHz microwaves. In these experiments, we observed that (1) optimum Binj>1.6~2 Bext, (2) optimum Br>1.2~1.4 Bext and (3) optimum Bext is dependent on the charge state and ion spices as described by scaling low. We also observed same tendency for 18 GHz liquid-He-free SC-ECRIS. Using this systematics, we obtained ~400μA of V13+ at the RF power of 2kW (28 GHz) and very low Bext (~1.4 T with 28 GHz). For long term operation (one month), we successfully produced very stable beam of 100~200 μA of V13+ ion. Following the success, we constructed new 28 GHz SC-ECRIS for super heavy element search experiments. In this contribution, we report the experimental results in detail and how to produce intense metal ion beams.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-ECRIS2018-TUA1  
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TUA3 New 28-GHz Superconducting ECR Ion Source for Synthesizing New Super Heavy Elements of Z > 118 53
 
  • T. Nagatomo, M. Fujimaki, N. Fukunishi, Y. Higurashi, O. Kamigaito, K. Kumagai, T. Nakagawa, J. Ohnishi, N. Sakamoto, A. Uchiyama
    RIKEN Nishina Center, Wako, Japan
 
  To increase the intensity of heavy-ion beams such as V and Cr for synthesizing new super heavy elements (SHE), we started to construct a new 28-GHz Superconducting ECR ion source (SC-ECRIS) for RIKEN Linear Accelerator (RILAC) in 2017. The new SC-ECRIS consists of fully SC magnets and is designed to produce the beams of more than a hundred µA. RILAC is also currently being upgraded by adding superconducting (SC) rf cavities. The beam losses not only in the cavities but also in the beam pipes neighboring them must be avoided to keep the environment in the cold section as clean as possible. Thus, the high-intensity beam with well-controlled emittance is required for this SHE project. To meet the requirement, we use a triplet slits to limit the transverse emittance of the beam in the low energy beam transport (LEBT). In this contribution, we report the recent developments and the property of the first beam extracted from the new 28-GHz SC-ECRIS.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-ECRIS2018-TUA3  
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WEB4 Practical Use of High-Temperature Oven for 28 GHz Superconducting ECR Ion Source at RIKEN 180
 
  • J. Ohnishi, Y. Higurashi, T. Nakagawa
    RIKEN Nishina Center, Wako, Japan
 
  In order to accelerate uranium beams at the RI-beam Factory (RIBF) at RIKEN, U35+ ions are extracted from a 28 GHz superconducting ECR ion source by using a high-temperature oven. Our high temperature oven uses a tungsten crucible joule-heated with a large DC current. The crucible is heated to a temperature of approximately 2000°C to achieve a UO2 vapor pressure of 0.1'1 Pa. We encountered the following problems since 2013: 1) the ejection hole of the crucible was blocked with UO2, 2) local over-heating in the upper and lower rods supporting the crucible, and 3) the supporting rods were bent and broken by an electromagnetic force because of the reduction of tungsten strength in the long-term operation at high temperature. We overcame the above problems, and moreover by doubling the volume of the crucible, the high-temperature oven has been used for the ion source operation for the RIBF experiments since the first use in the autumn of 2016. In this contribution, we report the design changes in the new crucible, and the results of the long-term operation. Moreover, we also present the practical use of the high-temperature oven for vanadium beams for the super heavy element search.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-ECRIS2018-WEB4  
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