In inertial confinement fusion, direct-drive scheme has the significant advantage of high laser-target energy coupling efficiency. However, it requires high drive symmetry and irradiation uniformity, which limit the further development of direct drive. Plasma thermal smoothing has a natural suppressing effect on the driving symmetry and hydrodynamic instability. The existing diagnostic method based on X-ray imaging is limited by spatiotemporal resolution, which hinders the plasma thermal smoothing characteristics with disturbance amplitude below 10μm, resulting in insufficient understanding of the thermal smoothing mechanism. In this report，we innovatively combines the existing one-dimensional VISAR technique with the high-precision push-pull structure to establish a four-phase interference imaging system using compact optical path design, and realize "point-to-point" data processing by combining self-developed image alignment and velocity extraction algorithms. High time resolution (≤10ps), high spatial resolution (~μm) can be achieved. This technique could be applied to studying the plasma thermal smoothing characteristics and strengthen our understanding on different smoothing parameters.
 

Optical diagnosis; High spatiotemporal resolution; Four-phase VISAR; Shockwave diagnosis;