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 At
8:26 on February 1, 2008, right before the completion of the second
phase commissioning of the BEPCII, the collision of the electron and
positron beams of 530mA by 530mA was realized.
The commissioning of the BEPCII was planed in three
phases. The phase one commissioning, which is with conventional magnets
in the interaction region (IR), was carried out from Nov. 12 2006 to
August 3, 2007. In this phase, 100mA by 100mA beam collision was
achieved with by*=5
cm, while the estimated luminosity reached the level of BEPC. Two rounds
of synchrotron radiation operation were arranged during the period.
 In
the summer of 2007, the superconducting magnets SIM¨s and new vacuum
chambers were installed into the IR. The second phase commissioning was
started from October 24, 2007. Here are the milestones of this phase of
commissioning: the first electron beam was stored on Oct. 25, while the
first positron beam stored on Oct. 31; the first e+e-
collision was realized with
by*=1.5
cm on Nov. 18. On December 30, electron and positron beams of 300mA were
stored simultaneously in each ring and 2´500mA
e+-e- collision was realized on Jan. 29 while the
luminosity measured by the two zero-degree luminosity detector is higher
than 1´1032cm-2s-1。
 The
injector linac has passed acceptance test organized by CAS with positron
injection rate higher than its design value of 50mA/min. in the storage
ring and 100mA/min. in maximum. The response matrix technique has been
applied and, as a result, the measured working points and Twiss
parameters were well agreed with the design values. Optimization of the
injection and RF parameters and application of the transverse feedback
system made the steady increment of beam currents in the rings possible.
By scanning the tunes, coupling and orbit at the interaction point, the
luminosity has been increased day by day. In the meantime, the beam
instabilities and vacuum chamber heating as well as background caused by
particle losses were intensively observed and studies along with the
increase of the beam current. The parasitic operation with a synchrotron
radiation wiggler imosed was successfully tested.
Now the
machine is switched to the dedicated synchrotron radiation mode. The
BEPCII will be operated as a light source for users till March 26, 2008.
The BESIII detector will be rolled into the interaction region during
the following two months. The third phase commissioning of the BEPCII
will be started in June together with BESIII detector. Its target
luminosity is 30% of the design specification, i.e. 3´1032cm-2s-1.
Success of the second phase commissioning has given us a confidence to
reach this very challenging goal.
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