Initial stages of hydrodynamic expansion of plasma heated by intense laser radiation

The hydrodynamic equations describing the average behavior of a one‐dimensionally expanding plasma heated by laser radiation are solved analytically. For the small parameter approximation, the hydrodynamic expansion depends on the parameter ${\text{(16P/9Ml}}_0^2{)}^{\text{1/3}}{\tau }_L$ , where P is the laser power, M is the plasma mass, l₀ is the initial plasma length, and τ_L is the laser pulse duration. With τ_L=τ_ei, the electron ion relaxation time, it is possible to compute ${\phi }_{\max }{\text{\hspace{0.17em}(≈5.6×10}}^{\text{−6}}{n}_0^4{l}_0^3{m}_i{T}^{\text{−9/2}}$ , where m_i is the plasma ion mass and T is the temperature), the maximum flux density below which the hydrodynamic expansion may be neglected. We find that a 5‐kJ 75‐ns neodymium glass laser is capable of acheiving break‐even conditions for a 50% mixture of deuterium‐tritium gas.