Suppression of HOM's on a Prototype Superconducting Cavity by Absorbers

Higher-order modes (HOM's) excited in the Superconducting Cavity (SCC) can be damped through many ways. Microwave absorbers, HOM' s couplers, coaxial waveguides and other devices are used to achieve this aim. The recent status of the R&D on an 800MHz Prototype SCC being developed is presented in this paper. For the cavity, the HOM' s damping by absorbers is obtained with the large beam duct. A low power measurement on a prototype cavity has been carried out and the Q-values of HOM's are confirmed to be drastically reduced. Two types of ferrite as absorbers are investigated to achieve the function of damping the HOM' s. The modes we concerned focus in the range of 0.8-2.7GHz. By means of changing the parameters of the ferrite used in the cavity, a conclusion about the damping is acquired . Measurements indicate that most of the HOM' s in this range are effectively absorbed and damped at the presupposition that the basic mode is not affected. A few special modes are pointed out, which cannot be absorbed by means of absorbers because they cannot propagate out of the cavity. The two types of ferrite used in this project have similar property with the same value of B, equal to 1500Gs and the different values of e equal to 14, 16 respectively. In order to study the relation between the parameters of ferrite and the damping effect, further research will be carried out sequential- ly.