  In bubble-assisted Liquid HoleMultipliers(LHM), developed for noble-liquid
radiation detectors, the stability of the bubble and the electro-mechanical
properties of the liquid-to-gas interface play a dominant role in the detector
performance. A model is proposed to evaluate the static equilibrium
configurations of a bubble sustained underneath a perforated electrode immersed
in a liquid. For the first time bubbles were optically observed in LAr; their
properties were studied in contact with different material surfaces. This
permitted investigating the bubble-electrodynamics via numerical simulations;
it was shown that the electric field acts as an additional pressure term on the
bubble meniscus. The predictions for the liquid-to-gas interface were
successfully validated using X-ray micro-CT in water and in silicone oil at
STP. The proposed model and the results of this study are an important
milestone towards understanding and optimizing the parameters of LHM-based
noble-liquid detectors.
