  Shanghai Laser Electron Gamma Source, a $\gamma$-ray beam line of 10MeV order
was proposed recently. The beam line is expected to generate $\gamma$-ray with
maximum energy of 22MeV by backward Compton scattering between CO$_2$ laser and
electron in the 3.5GeV storage ring of future Shanghai Synchrotron Radiation
Facility. The flux of non-collimated $\gamma$-ray can be 10$^9$ $\sim$
10$^{10}$s$^{-1}$ if a commercial CO$_2$ laser of 100W order output power is
employed and injected with optimized settings.
