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Explosive lensing is used for instance in nuclear weapons. Several chemical charges are placed around the central core of fissile material. The shock waves caused by the chemical charges are focused by materials with a different index of refraction, acting like lenses, to create a shock wave that converges on the core, compressing it to ignite the main explosion.
This simulation shows a simplified, two-dimensional set-up, in which the primary shock waves are modeled by repeated pulses, originating from six points placed on the vertices of a regular hexagon. Six lenses are set around the central point, in such a way that the waves are focused there. Their index of refraction is given by 2.14, and has been chosen in such a way that the focal points of the lenses are located at the central point and at the sources of the pulses. The lenses have been chosen symmetrical here, but in practice often strongly asymmetrical lenses are used. Also, the primary charges are usually placed in an outer container, to direct more energy towards the center.This is like ASMR to me.
It's kind of unsettling to me.