  A unique facility for laser plasma physics and advanced accelerator research
has been built recently at Tsinghua Universtiy. This system is based on
Tsinghua Thomson scattering X-ray source (TTX), which combining an ultrafast TW
laser with a synchronized 45MeV high brightness linac. In our recent laser
wakefield acceleration experiments, we have obtained 10~40MeV high quality
monoenergetic electron beams by running the laser at 5TW peak power. Under
certain conditions, very low relative energy spread of a few percent can be
achieved. Absolute charge calibration for three different scintillating screens
has also been performed using the linac system.
