Electromagnetic simulations, manufacturing and low power measurements of a 352.21 MHz RF power coupler for the SANAEM RFQ project

Radio frequency quadrupole (RFQ) linear accelerators occupy an important place among modern accelerators since the days it was conceived and constructed because of its ability to focus, bunch and accelerate the low energy beams at high efficiency. In Turkey, recently a 352.21 MHz RFQ accelerator cavity is designed and manufactured within a proton beamline located at the Turkish Atomic Energy Authority (TAEK), Saraykoy Nuclear Research and Training Center (SANAEM). The SANAEM RFQ cavity, operating in pulsed mode needs an overall RF power of 120 kW to accelerate the proton beam up to a final beam energy of 1.3 MeV. A new prototype RF power coupler, considering multipacting effect is designed, developed and manufactured to be used to deliver the required power for the RFQ. At the beginning of this study, design and 3D EM simulations of a coaxial power coupler considered for the SANAEM RFQ accelerator is presented. The RF properties of the coupler such as external quality factor, power loss on the loop, coupling coefficient and scattering parameters are evaluated and the geometrical parameters are optimized with the CST Microwave Studio. Also, various dielectric window materials to be used in the coupler are discussed. Moreover, multipacting simulations for the coupler are carried out using the CST Particle Studio and RF power levels at which the multipacting effect occurs are obtained. Finally, the manufacturing of a prototype coupler, low power measurements and discussions are presented in the present article.