Results of experiments on quasi-isentropic compression of deuterium and helium to extreme pressures of $\approx$3000 GPa

Experiments were performed to study the spherical compression of deuterium and helium to pressures of $\approx$3000 GPa in a quasi-isentropic regime. The process was recorded by a multi-frame radiographic system which produces up to nine X-ray images of a cavity with gas at various times in one experiment. X-ray images show that explosive devices provide a cavity shape close to spherically symmetric with gas up to the maximum compression of the gas. The experimental data are in good agreement with the results of calculations performed using the RFNC-VNIIEF equations of state of the gases studied. The results of these calculations are used to determine the parameters of the region of compressed gas states reached in the experiments: for deuterium, density 5.5 g/cm$^3$ and pressure 3.6TPa; for helium, density 4.7 g/cm$^3$ and, pressure 2.4 TPa.