Working principles of the energy measurement system at BEPCII

The proposed beam energy measurement system at BEPCII is composed of three parts: the laser source and optics system, the laser-electron interaction system and the HPGe detector system. The working principles of each system are expounded together with the calculation for preliminary design. The normalizations of laser and electron beams are put forth and used for the evaluation of intensity of the backscattering photon. The simulation of HPGe detector is also performed for understanding the working properties.