Design of an RF Reference Distribution System for the RISP Linac

The heavy-ion accelerator of the Rare Isotope Science Project (RISP) in Korea has been developed. The RF reference distribution system must deliver phase reference signals to all low-level RF (LLRF) systems and BPM systems with low phase noise and low phase drift. The frequencies of the RISP linac are 81.25 MHz, 162.5 MHz and 325 MHz, and 30 LLRF systems and 60 BPMs are used for SCL3, and 210 LLRF systems and 60 BPMs are used for SCL2. A signal with a frequency of 81.25 MHz is chosen as the reference frequency signal, and a 1-5/8″ rigid coaxial line is installed with temperature control. This paper address aspects of the design for the RF reference distribution system, such as the reference frequency, phase noise on master oscillator, phase stability, temperature influence, and reference line attenuation.