We present the MIGA experiment, an underground long baseline atom interferometer to study gravity at large scale. The hybrid atom-laser antenna will use several atom interferometers simultaneously interrogated by the resonant mode of an optical cavity. The instrument will be a demonstrator for gravitational wave detection in a frequency band (100 mHz–1 Hz) not explored by classical ground and space-based observatories, and interesting for potential astrophysical sources. In the initial instrument configuration, standard atom interferometry techniques will be adopted, which will bring to a peak strain sensitivity of at 2 Hz. This demonstrator will enable to study the techniques to push further the sensitivity for the future development of gravitational wave detectors based on large scale atom interferometers. The experiment will be realized at the underground facility of the Laboratoire Souterrain à Bas Bruit (LSBB) in Rustrel–France, an exceptional site located away from major anthropogenic disturbances and showing very low background noise. In the following, we present the measurement principle of an in-cavity atom interferometer, derive the method for Gravitational Wave signal extraction from the antenna and determine the expected strain sensitivity. We then detail the functioning of the different systems of the antenna and describe the properties of the installation site.

Traditional Eulerian approaches to solute transport generally require very fine discretization of the transport Since the first attempts some 20 yr ago in the field of hydrology, domain to overcome recurrent problems of unstable nurandom walk (RW) particle tracking as applied to solute transport has experienced profound changes. Concepts and mathematical tech-merical solutions and/or artificial diffusion. Solving such niques have improved to the point that numerically difficult problems problems generally imposes a heavy computational bur-(e.g., advection-dominated transport in highly heterogeneous media, den. If the discretization is too coarse, oscillations and or reactive transport) are now much easier to address. Random walk numerical diffusion of standard Eulerian methods may has never been widely used for multiphase flow, probably because yield poor or even incorrect solutions, particularly when numerical dispersion is not a major problem for modeling exercises nonlinear processes such as multiphase flow or adsorpat large scales. However, vadose zone hydrologic studies often point tion-desorption are considered in conjunction with stanout very strong variations in fluid velocity over relatively short disdard advective-dispersive transport. This problem proved tances. Random walk methods may be well suited for such studies, to be crucial in safety calculations of underground reposa possibility which motivated us to write this review. We first give a comitory sites for nuclear wastes. To address these problems, prehensive discussion of the theoretical context of the method. The Fokker-Planck-Kolmogorov equation (FPKE) is established for sol-several alternative Eulerian-Lagrangian schemes based ute transport, as well as the ordinary Langevin equation and its simpli-on particle tracking have been developed, such as the fications for transport of small particles (e.g., colloids). Next, numerimethod of characteristics (Konikow et al., 1996). Partical methods are developed for the motion of particles in space. An cle tracking has also been used for numerical integration important section is subsequently dedicated to recent RW concepts in more complicated schemes, such as the Eulerian Lain the time domain, and to their application to anomalous (non-Fickian) grangian localized adjoint method (ELLAM) (Russell transport and inverse problems. Adaptations of RW to transport with and Celia, 2002; Younè s, 2004). solute-solid reactions are also provided, as well as several numericalWe provide a review of the principles of fully Lagranrecipes for resolving a few computational difficulties with the RW gian schemes based on RW particle tracking for solving method. We purposely did not include any comparisons with Eulerian advection-dispersion problems. Lagrangian approaches and Lagrangian approaches. These approaches are discussed at length in several references cited in this review. We note, however, that today's have long been used widely in physics for a variety of computing capabilities provide new incentives to using RW...

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We propose an adjustable modelling platform (KarstMod) for both the simulation of spring discharge at karst outlets and analysis of the hydrodynamics of the compartments considered in the model. KarstMod provides a modular, userfriendly modelling environment for educational, research and operational purposes. It can reproduce the structure of most conceptual lumped models of karst systems in the literature. The modularity of the platform allows to compare different hydrosystems within the same methodological approach. To promote good modelling practices, the platform provides a variety of graphs and tools that facilitate improved understanding and insights in the behaviour of the models, and that detect possible flaws in structure and parameterization. The model and users manual are freely downloadable from the SNO Karst website (www.sokarst.org)

Some portions of the porous rock matrix in the karst unsaturated zone (UZ) can contain large volumes of water and play a major role in water flow regulation. The essential results are presented of a local-scale study conducted in 2011 and 2012 above the Low Noise Underground Laboratory (LSBB-Laboratoire Souterrain à Bas Bruit) at Rustrel, southeastern France. Previous research revealed the geological structure and water-related features of the study site and illustrated the feasibility of specific hydrogeophysical measurements. In this study, the focus is on hydrodynamics at the seasonal and event time scales. Magnetic resonance sounding (MRS) measured a high water content (more than 10 %) in a large volume of rock. This large volume of water cannot be stored in fractures and conduits within the UZ. MRS was also used to measure the seasonal variation of water stored in the karst UZ. A process-based model was developed to simulate the effect of vegetation on groundwater recharge dynamics. In addition, electrical resistivity tomography (ERT) monitoring was used to assess preferential water pathways during a rain event. This study demonstrates the major influence of water flow within the porous rock matrix on the UZ hydrogeological functioning at both the local (LSBB) and regional (Fontaine de Vaucluse) scales. By taking into account the role of the porous matrix in water flow regulation, these findings may significantly improve karst groundwater hydrodynamic modelling, exploitation, and sustainable management.