Using modern X-ray sources with very high brilliance, each such 3D frame may be sampled at kHz rates at synchrotrons and even MHz rates at X-ray free-electron laser sources. This will unlock access to 4D observation of processes with velocities never before possible. 4D imaging of opaque samples at MHz rates enables insights across a range of sectors and industries. In cavitation peening, an industrially relevant phenomenon for aerospace and new materials, we have no volumetric information, due to its high speed. This breakthrough will be achieved by the construction of a prototype that will demonstrate MHz rate tomoscopy at the European XFEL, taking advantage of world-unique European laboratories for the benefit of industry.

Observing MHz-fast phenomena in opaque samples enables an entirely new branch of research, with possibilities for all sectors where such fast phenomena has, to date, been left to simulations and speculations. For industry and society, it would open new possibilities in the development and management of several techniques, including laser driven additive manufacturing, shock waves, fractures, evaporation, light alloy metallurgy, fast fluid dynamics, and cavitation phenomena.