Practical Use of High-Temperature Oven for 28 GHz Superconducting ECR Ion Source at RIKEN

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.
Proceedings of the 23th Int. Workshop on ECR Ion Sources, ECRIS2018, Catania, Italy