Yoon, J.Y. Bhang, J.B. Cha, H.J. Jang, S.W. Kako, E. Kim, D.Y. Kim, E.-S. Kim, K.R. Lee, J. Park, C.S. Park, S. H. Shin, I. JACoW Publishing Geneva, Switzerland 2226-0366 978-3-95450-194-6 10.18429/JACoW-LINAC2018-TUPO052 English 451-453 TUPO052 simulation pick-up cavity superconducting-cavity resonance Contribution to a conference proceedings 2019 2019-01 https://doi.org/10.18429/JACoW-LINAC2018-TUPO052 http://jacow.org/linac2018/papers/tupo052.pdf We present design studies of a prototype RF input power coupler, which provides RF powers to 325MHz cavities up to 18.5 kW in CW mode. The prototype power coupler is a coaxial capacitive type with single ceramic window. In order to optimize the RF coupler design, we performed multi-physics simulations, including electromagnetic, thermal, and mechanical analyses.