Successful Collision Realized in the Second Stage of BEPCII Commissioning

  The BEPCII storage ring started its second commissioning run on Oct. 24, 2007, with the superconducting quadrupoles installed in the interaction region. After the various parameters of the two rings being measured and optimized, the electron and positron beams collided successfully on Nov. 18, 2007, with the collision beam currents of 5.2 mA * 5.2 mA. As a milestone of the commissioning, it was the first time for the BEPCII to collide at the designed vertical beta function of 1.5 cm at the IP. It also means that the manufacture and upgrade of the equipment on the storage rings go to the end. All the key facilities satisfy the requirement of operation, with their designed specifications reached.