BEPCII-The Second Phase Construction of Beijing Electron Positron Collider

BEPCII, the second phase construction of the Beijing Electron Positron Collider (BEPC), is a double ring machine with a design luminosity of 1×10³³cm^-2s^-1at 1.89GeV, two orders of magnitude higher than present BEPC. The construction was started in the beginning of 2004 and is scheduled to be completed by the end of 2007. The upgrading of the collider should also provide an improved SR performance with higher beam energy and intensity. The beam currents will be increased to 250mA at E=2.5GeV for the dedicated synchrotron radiation operation. Some key technologies, such as superconducting RF cavity, superconducting micro-beta quadrupole and low impedance vacuum devices etc., are being developed in order to achieve the target of the BEPCII.