The Turkish Atomic Energy Authority (TAEK) is conducting a project for the construction of a radio frequency quadrupole (RFQ) cavity to accelerate protons in the range of 1 - 5 MeV energy at Saraykoy Nuclear Research and Training Center (SANAEM). The RF system of the project consists of an RF power supply unit, an RF transmission line with rectangular and coaxial waveguide parts, waveguide converters and a circulator. The whole line is terminated by a power coupler of coaxial type. In order to provide the power needed for the operation of the cavity, the right conditions must be satisfied by the power coupler. This coupler must handle a peak power of 120 kW in pulsed mode for the 352.21 MHz RFQ cavity. The present study focuses on the electromagnetic design of a new prototype power coupler for the determination of its materials and geometrical parameters using the CST Studio Suite. Moreover, simulations studies for multipacting in the coupler were performed with the same software.