Primary study of high order mode for superconducting accelerator under CW operation

The superconducting accelerator has high quality factor, so the decay time of the field emitted by beam is much longer than that in normal conducting cavity. This results in the strong interaction between the SC cavity and the beam through it. The high order mode field excited by short bunches could effect the beam and cause beam break up. In this paper, the total high order mode power of TESLA 9-cell cavity with the beam load of 1 mA was estimated．The result shows that the phase shifts of high ovder mode, referring to major eigen frequencies of the cavity, are more than π/4. There would be no resonant buildup. The total high order module power is in mW level.