This paper presents the results of studies of the acceleration of macroparticles consisting of fragments of matter from the back side of a solid target when its front surface is irradiated with a picosecond laser pulse with intensity 10¹³-10¹⁵ W/cm². It is experimentally shown that there are optimal conditions for maximizing the spalling momentum of the target fragments, depending on its thickness and the intensity of the laser pulse on the front surface. The focusing of melted fragments of the substance, split off from the back surface of a target made in the form of a hemisphere, is experimentally demonstrated. The spalling momentum from such a target is greater than the momentum from a flat target of the same thickness by a factor of 6 -7.