Abstract
A new concept of a tuning free cavity for an ion synchrotron is described, which is based on an idea of applying an all-pass network to a ferrite LC resonator. Though the new type cavity has a smaller and simpler structure than bias-tuned one, it can produce comparably high RF voltage and a wide frequency range. After high power tests of newly developed ferrite materials and a proto-type cavity proved the concept practicable, beam acceleration tests were performed at HIMAC successfully. The course of developing the cavity is described with its unique merits and further applicability.