Research on higher-order-mode (HOM) damping of superconducting cavities for the next-generation synchrotron light sources.

点击翻译按钮获取中文摘要

The superconducting (SC) linear accelerator (linac) is one of the key technologies for the next-generation synchrotron light sources. We investigated method of higher-order-mode (HOM) damping for superconducting cavities, that is, one of the important issues for the SC-linacs for preventing beam breakup (BBU) instabilities.We applied the HOM damping method using radial-transmission lines to the 9-cell 1.3-GHz cavities. We investigated the Q-values of the principal HOMs by computer simulations, as well as by rf measurements of model copper cavity. The Q-values of HOMs depended strongly on the distance between the radial line and the end of the cavity. For the monopole modes, such as TM011-like and TM020-like modes, typical external Q-values of about 10,000 were obtained. For the dipole modes, typical Q-values were about 10,000 and about 10,000-100,000 for the TE111-like and the TM110-like modes, respectively. The HOM damping due to this method was good on the whole, however, further improvements are desirable for the TM110-like modes. We are trying to improve this point by such method as enlarging the beam-pipe radius from 39 mm (present) to larger ones.From FY2005,the development of the energy recovery linac (ERL) for the next-generation synchrotron light sources started by collaboration between the High Energy Accelerator Research Organization (KEK) and the Japan Atomic Energy Agency (JAEA). A team for developing the SC cavities for this purpose was organized, and they started their research. The basic research results from our research are fully used for this purpose.