A method of imaging of ultra-fast processes, like explosion or fast combustion, at a synchrotron radiation beam is being developed at the Siberian Synchrotron and Teraherz Radiation Center (SSTRC). Two stations are operating at beam line 0 at the VEPP-3 storage ring and at beam line 8 at the VEPP-4M storage ring. Both stations are equipped with the detector for imaging of explosions DIMEX, based on high pressure ionization chamber, and allowing to record up to 100 one-dimensional images with the frame rate of 8 MHz. However, the maximum flux that DIMEX can detect is limited as well as spatial resolution and frame rate because of gas technology used. In view of significant increase of SR flux at the VEPP-4M beam line due to the new 9-pole 2 T wiggler, a new detector is being developed for this beam line, based on Si microstrip sensor. The first Si microstrip detector prototype has been mounted with new specially developed front-end ASIC that allows to record data with the rate of 50 MFrames/s. The first measurements with this prototype demonstrated significant improvement of all critical parameters of the detector compared to the gaseous version. The maximum detected photon rate before saturation is increased to ~10000 photons/(chan x bunch) compared to ~1000 photons/(chan x bunch) (Si detector has 50 Pm channel pitch while gaseous detector has 100 Pm channel pitch). Spatial resolution is improved from 250 Pm to 72 Pm and frame rate is increased by a factor more than 6.