Relaxation of Light Emission from Hot Spots Depending on the Characteristics of the Environment

Abstract

The light emission from samples consisting of a transparent matrix with inclusions of hot spots was studied. The matrix material was water and epoxy resin. Hot spots were generated by shock compression of MS-V hollow glass microballoons. In the pressure range 0.7–29 GPa, a brightness decay time of 280 to 70 ns was recorded. The brightness decay time increased by more than an order of magnitude when replacing the optical window made of solid epoxy resin by LiF. However, even this increased time of brightness decay is much shorter than the estimated times of hot-spot temperature relaxation due to heat conduction in the calculation with stationary parameters (\(t_{a} = 10^{- 2}\) s) and due to light emission (\(\tau = 2.4 \cdot 10^{-3}\) s). It is concluded that the dominant mechanism of temperature relaxation is the turbulent mixing of the medium behind the shock-wave front. The experimental results show that in numerical simulations of the temperature field during shock-wave propagation through a pore, it is necessary to take into account the viscosity and strength of the matrix material.