K. Akai

Development of high-power ARES cavities

The ARES (Accelerator Resonantly coupled with Energy Storage) structure is a three-cavity system operated in the /spl pi//2 mode, where a HOM-damped accelerating cavity is coupled with an energy storage cavity via a coupling cavity equipped with a coaxial antenna damper to reduce the impedances of the parasitic 0 and /spl pi/ modes. Two high-power prototypes with different HOM-damping schemes have been developed, where one is with a quadrupole counter-mixing (QCM) choke structure and the other with grooved beam pipe one. Both prototypes have been tested with an electron beam of about 500 mA in the TRISTAN accumulation ring. This paper reports their RF structures together with some results of the high-power and high-current beam tests.

HOM absorber for the ARES cavity

Two types of sintered SiC (silicon carbide) ceramics have been developed and applied as the HOM absorbers for the second prototype ARES cavity (ARES96). One is bullet-shape SiC ceramics and the other is a tile one. The prototype cavity equipped with these absorbers was successfully tested with an electron beam in the TRISTAN accumulation ring. High power tests of these absorbers were carried out using an L-band RF power source. The HOM absorber designs and the results of the tests are discussed.

Fundamental mode characteristics of ARES cavity under beam environment

Two types of ARES cavities were tested in the TRISTAN accumulation ring in KEK. In this paper, results relating to the fundamental mode in the accelerating cavity are reported. The status of the cavity, including the detuning frequency under beam loading and the output power from the coupling cavity damper, was measured at different beam current and with various bunch patterns. Its behavior agrees well with the calculation based on a coupled resonator model.

Coupling cavity damper for the ARES

The coaxial (WX120D) antenna damper has been developed for damping the parasitic 0 and /spl pi/ modes of the KEKB ARES cavity. It is installed in the coupling cavity of the ARES. The damper consists of a disk-type coaxial ceramic window and a cross stub angle. The damper has a broadband RF property in order to absorb the RF power of the parasitic modes. The cross angle is utilized for supplying the cooling water to the antenna. The damper was designed by using a computer simulation code without a cold model test. Finally the properties of the damper has been confirmed by the high-power and the beam test for the ARES cavity.