ИСТИНА

New ion beam experiments cycle for HED matter properties and EOS research is scheduled at FAIR facility. Based on previous HIHEX (Heavy Ion Heating and EXpansion) experiment results held at GSI [1] it was proposed to use the focused heavy ion beam for fast and uniform heating of thin metallic (Lead) foil, that melts, evaporates and expands to the sides in quasi-1-D regime. In order to reach closer to the main area of interest on the metal phase diagram - critical point (CP) and evaporation curve - it was supposed to use enclosing high-pressure assembly, filled with heavy transparent gas (Ar, initial pressure 100 bar). The shock wave generated in Ar by hot expanding Lead creates counter-pressure up to few kilobars, while remaining transparent. It allows one to use different registration and diagnostic techniques: pyrometry, interferometry, reflectivity measurement, shadowgraphy and schlieren shadowgraphy. From the announced list of feasible projectile beam configurations on the 2021 FAIR operation we chose U, Ni, Ar and N ion beams as the most promising for our goals, realistic intensities estimated for these beams were selected. Bunch duration is 100 ns with parabolic temporal distribution. Considering the geometry of the lead specimen 2-D Gaussian distribution for spatial beam focal spot was used, with fixed Sigmax=0.25 mm and varying Sigmay=0.5-1.5 mm. Staying in that range preserves high enough energy deposition value as well as quasi-1-D hydrodynamic flow regime even at the later stages of experiment. Multidimensional hydrodynamic implementation of finite size particle-in-cell method was used for 1- and 2-D modeling. SRIM-based ion stopping procedure was used for heavy ion beam energy deposition effect in the Pb-target and ambient Ar gas, using tabular wide-range multiphase equation of state for Lead [3]. The history of Pb-target material parameters were recorded during the numerical experiment. It was found that in order to get to near-critical point region states in Lead during expansion phase of the experiment the peak projected specific internal energy values in the target should be higher than 1 kJ/g. Thus only the usage of Ni ion beam with up to 1.E+11 particles looks appropriate and N, Ar and U beams with lower intensities are not sufficient. In order to estimate the level of intensity needed for the U ion beam, we simulate the impact of increased values of I=3.0E+09 and I=4.0E+09 particles/bunch. It was shown that for highly focused U beam with I=3.0E+09 the parameters in Lead in expansion phase of the experiment are at a lower end of the main area of interest, and higher beam energetic parameters are desirable. [1] D. Varentsov et al., Nucl. Instr. & Meth. in Phys. Res. A. 577(1-2) (2007) 262-266 [2] V.E. Fortov et al., Int. J. Impact Eng. 33 (2006) 244 [3] V.E. Fortov et al., Nucl. Instr. & Meth. in Phys. Res. A. 415, 3 (1998) 604-608