Liu, X. Chiche, R. Dupraz, K. Favier, P. Huang, W.-H. Martens, A. Monard, H. Nutarelli, D. Tang, C.-X. Yan, L.X. Zomer, Z.F. JACoW Publishing Geneva, Switzerland 978-3-95450-184-7 10.18429/JACoW-IPAC2018-THPMK115 English 4587-4589 THPMK115 Contribution to a conference proceedings 2018 2018-06 https://doi.org/10.18429/JACoW-IPAC2018-THPMK115 http://jacow.org/ipac2018/papers/thpmk115.pdf Laser-electron Inverse Compton Scattering X-ray source based on optical enhancement cavity is expected to produce higher-flux and better-quality X-rays than conventional sources, in addition, to become more compact, much cheaper than Free Electron Laser and Synchrotron Radiation. One X-ray source named ThomX is under construction at LAL, France. An electron storage ring with 50 MeV, 16.7 MHz electron beam will collide with a few picosecond pulsed laser to produce 10¹³ photons per second. A prototype cavity with a high finesse (F=25,100) in the picosecond regime is used to perform R & D for ThomX. We obtained 380 kW power stored in the optical cavity and mode instabilities were observed. The EOM-based frequency modulation to measure the finesse, the influence of dust on finesse, high-power experiments and other related issues are mentioned briefly. We will also describe the TTX2 (Tsinghua Thomson Scattering X-ray source) at Tsinghua University which is in design process. TTX2 prefers using an electron storage ring and an optical cavity in order to get high X-ray flux.