Surfaces of condensed matter, for example, the electrodes of pulsed power facilities, in some experiments are exposed to powerful X-ray pulses with an energy flux density of ~ 1 TW/cm². The source of this radiation can be, for example, Z-pinches formed during stagnation of multi-wire liner arrays. Evaporation and plasma formation processes can occur on the surface of the electrodes under the effect of this radiation. Theoretical study of these processes is carried out in this work. When the thickness of the plasma layer is small compared to the characteristic dimensions of the electrodes, plasma formation can be described by one-dimensional equations of hydrodynamics with the account for the radiation transfer. One-dimensional calculations for the experimental conditions at Angara-5-1 facility (energy flux density coming from the pinch is ~ 0.2 TW/cm², the time of the radiation pulse is ~ 15 ns, electrode material is Fe) have shown that the characteristic  plasma  temperature  in  this  case  is  ~ 40 eV,  the  plasma density  is ~ 10^-3 g/cm³, and its expansion velocity is ~ 60 km/s. It is interesting to note that the magnetic fields in these experiments, that are relatively small (~ 0.8 MG) and can’t result to plasma formation, restrain plasma expansion with their pressure and affect its characteristic values and its expansion velocity. The velocity obtained in the computation appeared to be slightly less than that measured in experiments using X-ray electron-optjcal converter (~ 90 km/s), that could be due to the non-one-dimensional turbulent plasma expansion.

Z-pinch, multi-wire liner array, X-ray pulse, plasma formation