STATUS AND PERFORMANCE OF BEPCII

BEPCII is the upgrade project of Beijing Electron Positron Collider (BEPC) with its design luminosity of 1×10 cms at the beam energy of 1.89GeV. The construction of BEPCII was completed in May 2008, when the detector worked together with the machine. The collider has been operating for high energy physics since May, 2009, and for synchrotron radiation users since 2007. The status and updated performance of BEPCII are reported here. INTRODUCTION BEPCII contains a linac, two transport lines and three storage rings. Among three rings, two are in parallel for e and e beams, respectively, and named as BER and BPR. It locates in the original tunnel of the collider, BEPC, using as many BEPC’s magnets as possible and keeping all the BEPC beam lines extraction ports unchanged. The collider was designed as a factory-like one with a design luminosity of 1×10cms at the beam energy of 1.89GeV. BEPCII is characterized as “one machine, two purposes”, which means to provide beam not only for high energy physics experiment, but also for synchrotron radiation (SR) users in parasitic or dedicated mode. The two halves of the outer rings are connected as an SR ring, the third ring named as BSR, with 9 beam lines extracted from 5 wigglers, and 6 beam lines from bending magnets, as shown in Fig. 1. Figure 1: Layout of the BEPCII storage rings. The linac finished its construction in 2004 and started commissioning in 2005. After the installation of storage rings for one and a half years, the commissioning of the rings started from Nov. 2006. Later, in 2007, the linac reached all the design parameters. Table 1 lists the main design parameters of BEPCII. In this paper, the linac upgrades are first described. Then the commissioning of the storage rings in last year is reviewed, and finally the operation of BEPCII for the users is given. Table 1: Main design parameters of the BEPCII Energy for collision GeV 1.89 Beam current in collision mA 910 Energy for SR GeV 2.5 Beam current in SR mA 250 Injection energy GeV 1.89 – 2.5 Injection rate (e, e) mA/min 50, 200