  The beam energy measurement system is of great importance and profit for both
BEPC-II accelerator and BES-III detector. The system is based on measuring the
energies of Compton back-scattered photons. Many advanced techniques and
precise instruments are employed to realize the highly accurate measurement of
positron/electron beam energy. During five year's running period, in order to
meet the requirement of data taking and improve the capacity of measurement
itself, the upgradation of system is continued, which involve the component
reformation of laser and optics subsystem, replacement of view-port of the
laser to vacuum insertion subsystem, the purchase of electric cooling system
for high purity germanium detector, and the improvement of data acquisition and
processing subsystem. The upgrading of system guarantees the smooth and
efficient measuring of beam energy at BEPC-II and accommodates the accurate
offline energy values for further physics analysis at BES-III.
