超导加速器由于具有极高的Q值,因此表现出较强的腔束相互作用,尤其是在以CW模式运行下,严重时会产生束流崩溃(BBU)效应.德国TESLA式的9-cell超导串腔在束流负载为1 mA,束团重复频率为81.25 MHz情况下,对其高阶模的产生及相应的功率水平进行了分析.结果表明:对于该腔的主要高阶模,谐振偏差值在π/4以上,束流没有发生谐振,高阶模功率在mW量级.

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, refering 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.