In this paper, we employ the upgraded two-dimensional arbitrary Eulerian-Lagrange (ALE) program MULTI-2D to simulate collision process of plasma jets with high speed (≥ 100 km/s) and high density (≥ 10 g/cc). Using the database obtained from the simulations, hydrodynamic scaling laws that describing the collision process of plasma jets are derived with the Bayesian inference method in machine learning. The Bayesian inference method not only has the parameter estimation function of traditional least square method, but also has other potential advantages such as giving the probability distribution of estimated parameters. Numerical results show that the collision of plasma jets with open boundaries is easy to form an isochoric plasma distribution with high-density. Increasing the initial density and velocity of the plasma jets is helpful to enhance the density and temperature of the colliding plasmas. Increasing the initial temperature of plasma jets is beneficial to achieve colliding plasmas with a higher temperature, while leading to a decreased plasma density and pressure after collision. When the initial density, temperature and velocity of the plasma jets are set to be 15 g/cc, 30 eV and 300 km/s, respectively, the colliding plasma density can reach more than 300 g/cc. This is very favorable for the following fast electron heating process in the double-cone ignition (DCI) scheme.
The issue about quantum degeneracy after collision is discussed in this work. Under the typical initial conditions of plasma jets in DCI scheme (100km/s ≤V0≤500km/s, 10eV ≤T0≤ 100eV, 10g/cc ≤ρ0≤ 50g/cc, both quantum degenerate plasma and classical non-degenerate plasma can be obtained with the temperature between 0.3TF (Fermi temperature) and 3TF. By comparing the plasma temperature and Fermi temperature of the collision, the criterion for achieving quantum degenerate plasma or non-degenerate plasma under given initial conditions is obtained with the help of the derived hydrodynamic scaling laws. The criterion shows that higher initial velocity, higher temperature and lower density of plasma jets are required if we want to obtain non-degenerate plasma after collision.
According to the results of the characterization parameters of local atomic structures (pair distribution function, coordination numbers, chemical short-range order, Voronoi polyhedron index, local five-fold symmetry, and mean square displacement), it is found that the GFA of the four alloys is different due to their different local atomic structures. Co72Y3B15C10 and Co72Y3B15P10 alloys possess a higher fraction of prism structures, and the solute segregation between B/C-C and B/P-P atoms is weak, resulting in the higher atomic diffusivity in the supercooled state (1100 K), and hence weaken the GFA of the alloys. The Co72Y3B15Si10 alloy has a higher fraction of icosahedral-like structures, the stronger attraction between Co-Si atoms and solute segregation between B/Si-Si atoms reduce the atomic diffusivity in the supercooled state, whilst improving the thermal stability of alloy melts, stability of the local atomic structures, and the degree of five-fold symmetry, thereby increasing the GFA. Based on the analysis of the local atomic structures, it is speculated that the addition of Si is beneficial for enhancing the GFA, while the addition of C or P will reduce the GFA, that is, the GFA of the four alloys decreases in the order of Co72Y3B15Si10 > Co72Y3B25 > Co72Y3B15P10 > Co72Y3B15C10. In terms of magnetic properties, with metalloid elements M addition, the total magnetic moment of Co72Y3B15M10 (M=B, C, Si, P) alloys decreases as follows Co72Y3B25 > Co72Y3B15Si10 > Co72Y3B15C10 > Co72Y3B15P10. The stronger p-d orbital hybridization between Co-Si atoms enhances the ferromagnetic exchange interaction, leading to the total magnetic moment less affected by Si addition.