Koser, D. Gerhard, P. Groening, L. Kester, O.K. Podlech, H. JACoW Geneva, Switzerland 978-3-95450-182-3 10.18429/JACoW-IPAC2017-THPIK021 English 4142-4144 THPIK021 Contribution to a conference proceedings 2017 2017-05 http://dx.doi.org/10.18429/JACoW-IPAC2017-THPIK021 http://jacow.org/ipac2017/papers/thpik021.pdf The High Charge State Injector (HLI) at the GSI Helmholtz Centre for Heavy Ion Research in Darmstadt, Germany, serves as one of the two injector linacs for the UNILAC as well as dedicated injector for the upcoming cw linac project for super heavy element research. As the front end of the HLI is planned to be upgraded for cw operation a newly revised cw capable RFQ structure with an operating frequency of 10⁸ MHz is required. The existent 4-rod structure, which was commissioned at the HLI in 2010, suffers from severe modulated rf power reflections originating from mechanical oscillations of the electrodes that both limit the achievable performance and impede stable operation*. Besides preceding vibration measurements that were done by GSI using a laser vibrometer**, the structural mechanical behavior of the 4-rod geometry was extensively analyzed using ANSYS Workbench. Thereby the crucial mechanical eigenmodes could be identified and their impact on the rf properties was investigated by simulations using CST MWS. A completely newly revised 4-rod RFQ design with optimized structural rigidity was developed of which a 6-stem prototype is currently being manufactured.