Superconducting RF activities at Peking University

High brightness electron beams are required for a number of applications including short wavelength FELs. As superconducting photoemission source appears to be promising in producing high current, low energy spread, high brightness electron beams, it is suggested to develop a high brightness superconducting rf gun of photo cathode by joint efforts of related institutes in China. For this purpose the RF superconducting group at IHIP of Peking University decided to gear their activities in developing Nb cavities for high brightness electron sources. As a start a series of efforts have been made since fall 1988 to construct a class 100 laboratory suitable for processing and assembling of Nb cavities, as well as to develop equipment and techniques for designing, surface treatment and RF test of superconducting cavities. The fields of fundamental and high-order modes, as well as wake field potentials, were studied using the SUPERFISH, URMEL and TBCI codes during design. Two high-purity L-band Nb cavities were kindly sent to them from DESY and Cornell to facilitate the development. In this paper the preparation of the Nb cavity made by Donier and the structure of the cryostat is described and preliminary results of Q versus temperature are presented and discussed. An accelerating field of 8.6 Mv/m was obtained with a Q0 of 6.5 x 108 at 2.25k