Self-similar multishock implosions for ultrahigh compression of matter.

We present a class of self-similar solutions describing ultrahigh compression of a uniform-density target by spherically converging, stacked shock waves. Extending the classical Guderley model, we derive a scaling law for the final density of the form ρ_{r}/ρ_{0}∝P[over ̂]^{β(N-1)}, where N is the number of shocks, P[over ̂] the stage pressure ratio, and β a numerical exponent determined by the adiabatic index γ. One-dimensional hydrodynamic simulations confirm the validity of this scaling across a broad parameter range. Notably, the relation remains accurate even in the strongly nonlinear regime up to P[over ̂]∼70, well beyond the perturbative limit, highlighting the robustness and practical relevance of the model. Owing to its volumetric geometry, this compression scheme inherently avoids the Rayleigh-Taylor instability, which typically compromises shell-based implosions, and thereby establishes a theoretical benchmark for instability-free compression in inertial confinement fusion.