CONSTRUCTION OF 714 MHZ HOM-FREE ACCELERATING CAVITIES

A new 'higher-order-mode (HOM)-free' accelerating cavity has been deve loped which can provide an accelerating voltage of more than 400 kV pe r cavity at a frequency of 714 MHz. The harmful HOMs in the cavities, which can induce beam instabilities at high beam currents, were heavil y damped by using four special waveguide ports and broadband microwave loads. Two cavities of this design were installed in the 1.54 GeV acc elerator test facility (ATF) damping ring at KEK, and successfully sto red beams. This cavity will also be very useful for synchrotron light sources. The basic design, characteristics of HOMs and construction of this cavity are reported.