Recent 28GHz Results with VENUS

Abstract: The next generation, superconducting ECR ion source VENUS (Versatile ECR ion source for NUclear Science) has operated with 28GHz since 2004, and has produced world record ion beam intensities. The VENUS project is focused on two main objectives. First, for the 88-Inch Cyclotron, VENUS will serve as the third injector source boosting both the energy and intensity of beams available from the facility. Secondly, VENUS also serves as the prototype injector source for a high intensity heavy ion beam driver linac for a next generation radioactive ion beam facility, where the goal is to produce intense beams of medium to low charge states ions such as 240eμA of Xe²⁰⁺ or 250eμA of U^28+to34+. These high intensity ion beam requirements present a challenge for the beam transport system since the total currents extracted from the ECR ion source reach several mA. Therefore in parallel to ion beam developments, we are also enhancing our ion beam diagnostics devices and are conducting an extensive ion beam simulation effort to improve the understanding of the ion beam transport from the VENUS ECR ion source. The paper will give an overview of recent experiments with the VENUS ECR ion source. Since the last ECR ion source workshop in Berkeley in 2004, we have installed a new plasma chamber, which includes X-ray shielding. This enables us to operate the source reliably at high power 28GHz operation. With this new chamber several high intensity beams (such as 2.4mA of O⁶⁺, 600eμA of O⁷⁺, 1mA of Ar⁹⁺, etc.) have been produced. In addition, we have started the development of high intensity uranium beams. For example, 200eμA of U³³⁺ and U³⁴⁺ have been produced so far. In respect to high charge state ions, 1eμA of Ar¹⁸⁺, 133eμA of Ar¹⁶⁺, and 4.9eμA of U⁴⁷⁺ have been measured. In addition, ion beam profile measurements are presented with, and without the sextupole magnetic field energized. These experimental results are being compared with simulations using the WARP code.