During the interaction of an intense picosecond laser pulse with a plasma created by a plastic foil ablated by a nanosecond laser pulse, relativistic electrons are produced. A metal solid target placed behind the foil allows converting these high-energy electrons into hard X-rays. The use of an ablated CH foil allows maximizing the conversion efficiency and thus the X-ray emission. In this study, the photon energy spectrum and dose are measured for different thicknesses of various metal targets such as tantalum. Numerical simulations including hydro-dynamical radiative, particle-in-cell, and Monte Carlo codes are made to give comparison with the experimental data. These are also compared with that of a bremsstrahlung emission and photon dose model in which the energy loss by Ohmic heating arising from the return current driven by the background electrons of the conductive target is taken into account [A. Compant La Fontaine, Phys. Plasmas 25, 043301 (2018)]. The results obtained allow for benchmarks to test the accuracy of this model and to check that the dose is maximized for high-Z solid targets and thickness in the mm range in the relativistic interaction regime at ultrahigh laser intensity (>10 18 W/cm 2). Published under license by AIP Publishing. https://doi.Read less <