RF SYSTEM FOR VEPP-5 DAMPING RING N. Alinovsky, D. Bolkhovityanov, V. Dolgashev, V. Kuptsov, G. Kurkin, I. Makarov, O. Nezhevenko , A. Nikiforov, S. Nosyrev, V. Osipov, G. Ostreiko, V. Parkhomchuk, B. Persov, V. Polukhin, I. Sedlyarov, G. Serdobintsev, A. Shteinke, V. Tarnetsky, N. Zapyatkin, Budker Institute of Nuclear Physics Novosibirsk, Russia Abstract RF system with operating frequency 700 MHz was de- veloped for the damping ring of the VEPP-5. The block diagram and elements descriptions are presented. Calcu- lated and measured parameters of the accelerating cavity are given. 1 INTRODUCTION The damping ring of the VEPP-5 facility [1, 2] was de- signed to provide accumulation, cooling, and extraction of electron and positron beams at energy 510 MeV with par- ticle production rate per second. Preinjector is a 510 MeV linear accelerator (f=2856 MHz). Compen- sation of synchrotron radiation energy losses is provided by a 700 MHz cavity. RF frequency is 64-th harmonic of the particle revolution frequency. Block diagram of the RF system is shown in Fig.1. It consists of RF power source, circulator, transmission waveguide, and RF cavity. H O 2 H O 2 G ref inc 50 dB inc ref 50 dB KU-393 100 kW U 18-30 kV RF cavity H O 2 Figure 1: Block diagram of damping ring RF system. 2 RF POWER SOURCE RF power source is a CW 100 kW klystron KU-393. Main operating parameters of the klystron are listed in Table 1. The klystron is powered by 200 kW six-phase rectifier. The voltage is controlled by thyristors. A resistor is incor- porated into the cathode circuit to prevent damage of the klystron by discharges. Klystron solenoid consists of five coils each powered by individual power source. Coils are Table 1: RF source parameters Frequency, MHz 700 Beam voltage, kV 27 Beam current, A 5.4 Output power, kW 65 Efficiency, % 45 Gain, dB 46 Perveance, A/V 1.23 placed into the same shield to decrease scattered magnetic field. General layout of the klystron section is shown in Fig.2. Figure 2: General view of klystron section. 3 WAVEGUIDE AND CIRCULATOR RF power is transmitted through a rectangular aluminium waveguide WR-1150 (292.1 146.05). Attenuation of the waveguide is about 0.0035 dB/m. Waveguide section con- tains E and H turns. Since the klystron output and cavity input have a coaxial design waveguide-to-coax transition has been produced (see Fig.3). A frequency dependence of VSWR of the transition is shown in Fig.4. Directional cou- plers in the transmission section are used for high power RF measurements. A CW 100 kW circulator developed in RSC “Domen” was incorporated into waveguide section to decouple the 1799