The beam energy calibration system for the BEPC-II collider
  This document contains a proposal of the BEPC-II collider beam energy calibration system (IHEP, Beijing). The system is based on Compton backscattering of carbon dioxide laser radiation, producing a beam of high energy photons. Their energy spectrum is then accurately measured by HPGe detector. The high-energy spectrum edge will allow to determine the average electron or positron beam energy with relative accuracy about 3x10^-5. 
M.N.Achasov, ChengDong Fu, Xiaohu Mo, N.Yu.Muchnoi, Qing Qin, Huamin   Qu, Yifang Wang, Jinqiang Xu