Inertial Confinement by Centimetric Cavity Collapse – IC4

Our work is based on the analysis of experiments. We take advantage of an original process, that allows for creating large nearly void spherical cavities inside several liquids (water, glycerin, oxygen)

We have shown that for 2D bubbles, mass transfers from the bubble core to the wall are limited by diffusion. For 3D bubbles, transfers are faster. This let think that a flow exists in the bubble inner.

We will develop experimental features :
- well controlled cryogenics experiments
- Adapted spectrometric techniques

This will allows for a better understanding of the process physics.

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We intend to study the dynamics of inertial confinement: when a cavity in a liquid bulk is strongly depressed compared to its surroundings, it collapses, forcing a convergent flow of the external medium towards the center of the cavity. The matter possibly trapped inside the cavity is highly compressed and the inner temperature is likely to reach very high levels. This process is used in the context of inertial confinement for atomic fusion (ICF). It is also at play in the
sonoluminescence context.
We propose a new experimental scheme, allowing forming quasi-empty large cavities (a few centimeters). The typical collapse timescale is also long (a few milliseconds), so that a direct observation of nearly all the physical phenomena involved is possible. A bubble composed of a reactive hydrogen-oxygen mixture (with optional inert gas) is formed in various liquids (liquid oxygen, water, glycerin,…). The bubble is spherical when the effects of gravity are attenuated, or canceled (by magnetic levitation, or by free fall). The combustion of reactive mixture is triggered, and the latter is transformed in water vapor, which condenses on the bubble walls. Then, the cavity containing inert gases collapses, and the inner pressure and temperature elevate strongly. The project objectives are multiple. First, we intend to determine the exact value reached by the inner temperature and pressure at the maximal compression point
and to study the effect of all intermediate processes.
The heat and mass transfer mechanisms at the interface and the mixing process induced by the interface acceleration determine the composition of the confined medium. The hydrodynamical mechanisms will also be described (in particular the interface stability will be discussed). A good understanding of these aspects is necessary to optimize the confinement process and to reach the most extreme conditions. This hydrodynamical analogue of the ICF configuration, as the analysis of the mixing process induced during the condensation process will improve our knowledge and help in the control of ICF experiments.