Simulation of higher order modes and loss factor of a new type of 500-MHz single cell superconducting cavity at SSRF

In this paper, higher order modes (HOMs) and loss factor of a new type of 500-MHz superconducting cavity is studied, by simulating its broadband HOMs damping at different positions of the ferrite HOM-absorber and different lengths of the ferrite. The results show that the impedance and Q value of the HOMs in transverse and longitudinal modes could be greatly reduced. The HOM longitudinal impedance could be damped to meet the requirement of SSRF beam instability threshold. The calculated loss factor of the new SC cavity was compared with cavities at SSRF. It was estimated that the HOM absorber could absorb a total power of 3.16 kW at 4-mm beam bunch length.