北京正负电子对撞机储存环真空系统运行和改进

Operation and improvement of vacuum system of BEPC storage ring

目前BEPC储存环真空系统已经运行了十五年,系统运行良好,当有束流存在时,储存环的平均动态压强低于2.6×10-7Pa,束流寿命大于10 h。尽管真空系统部件多,结构复杂,但由于真空泄漏造成停机的次数并不多,大多数的泄漏能在抽真空和系统检漏期间排除。为了提高北京正负电子对撞机的性能,BEPC储存环真空系统进行了一系列的改进,例如,重新改造铝真空盒用来引出同步辐射光束线,在正负电子对撞区安装NEG泵来提高真空度。特别是真空内的扭摆磁铁被安装到储存环真空系统,通过在永久磁块表面镀氮化钛和合理的排气技术,静态压强已经达到了2.6×10-8Pa。

The vacuum system of BEPC storage ring has run well for 15 years by now, of which the mean dynamic pressure was over 2. 6×10^- 7Pa in the presence of circulating beams for which the lifetime was over 10hr. The occurrence of leaks has been rare in spite of a large number of individual components in the vacuum system, Most of leaks can be eliminated during the first pump down and overall leak check of a vacuum sector, In order to improve the performance of BEPC, the vacuum system of BEPC storage ring has been upgraded systematically, such as remaking the aluminum vacuum chambers to lead out synchrotron radiation light beam, installing NEG pumps in the interaction region to decrease vacuum pressure, Especially the in-vacuum magnet wiggler has been mounted into the vacuum system of BEPC storage ring and the static pressure has been up to 2.6 × 10^-8Pa by coating TiN on the surface of the permanent-magnet blocks with reasonable pump-down technique provided.