Thermodynamic properties of a nonideal helium plasma at quasi-isentropic compression by a factor of 575 at a pressure of 3000 GPa

The quasi-isentropic compressibility of a nonideal helium plasma has been measured in a two-cascade spherical chamber with separated cavities with the use of an explosive charge with the mass of a parts per thousand 55 kg. The experiment has been performed on an X-ray diffraction complex consisting of three betatrons and a multichannel optoelectronic system for recording X-ray images. The density of the compressed helium plasma measured at the initial pressures of the gas in the outer and inner cavities P (1) = 36.4 MPa and P (2) = 5.1 MPa, respectively, is rho = 4.6 g/cm(3), which corresponds to the degree of compression sigma = 575 at pressure Pa parts per thousand 3000 GPa under the condition of strong nonideality (gamma similar to 7) and noticeable degeneracy of electrons (n lambda(3) similar to 5). The pressure of compressed helium has been determined from the results of the gas-dynamics calculation.