Mesoscopic Correlation with Polarization of Electromagnetic Waves

Mesoscopic correlations are observed in the polarization of microwave radiation transmitted through a random waveguide. These measurements, supported by diagrammatic theory, permit the unambiguous identification of short, long, and infinite range components in the intensity correlation function, as well as an additional frequency-independent component.Comment: 4+ RevTex pages, 4 figure

Information transfer through disordered media by diffuse waves

We consider the information content h of a scalar multiple-scattered, diffuse wave field $\psi(\vec{r})$ and the information capacity C of a communication channel that employs diffuse waves to transfer the information through a disordered medium. Both h and C are shown to be directly related to the mesoscopic correlations between the values of $\psi(\vec{r})$ at different positions $\vec{r}$ in space, arising due to the coherent nature of the wave. For the particular case of a communication channel between two identical linear arrays of $n \gg 1$ equally-spaced transmitters/receivers (receiver spacing a), we show that the average capacity $\propto n$ and obtain explicit analytic expressions for $/n$ in the limit of $n \to \infty$ and $k \ell \to \infty$, where $k= 2\pi/ \lambda$, $\lambda$ is the wavelength, and $\ell$ is the mean free path. Modification of the above results in the case of finite but large n and $k \ell$ is discussed as well.Comment: REVTeX 4, 12 pages, 7 figure

Phenomenological Study of Strong Decays of Heavy Hadrons in Heavy Quark Effective Theory

The application of the tensor formalism of the heavy quark effective theory (HQET) at leading order to strong decays of heavy hadrons is presented. Comparisons between experimental and theoretical predictions of ratios of decay rates for B mesons, D mesons and kaons are given. The application of HQET to strange mesons presents some encouraging results. The spin-flavor symmetry is used to predict some decay rates that have not yet been measured.Comment: 10 page

Quasi Two-dimensional Transfer of Elastic Waves

A theory for multiple scattering of elastic waves is presented in a random medium bounded by two ideal free surfaces, whose horizontal size is infinite and whose transverse size is smaller than the mean free path of the waves. This geometry is relevant for seismic wave propagation in the Earth crust. We derive a time-dependent, quasi-2D radiative transfer equation, that describes the coupling of the eigenmodes of the layer (surface Rayleigh waves, SH waves, and Lamb waves). Expressions are found that relate the small-scale fluctuations to the life time of the modes and to their coupling rates. We discuss a diffusion approximation that simplifies the mathematics of this model significantly, and which should apply at large lapse times. Finally, coherent backscattering is studied within the quasi-2D radiative transfer equation for different source and detection configurations.Comment: REVTeX, 36 pages with 10 figures. Submitted to Phys. Rev.

Energy partition of seismic coda waves in layered media: theory and application to Pinyon Flats Observatory

We have studied the partition of shear, compressional and kinetic energies in the coda of ten earthquakes recorded on a dense array, located at Pinyon Flats Observatory (PFO), California. We observe a clear stabilization of the shear to compressional ($W^s/W^p$) energy ratio in the coda, with an average value of about 2.8. The ratio between the vertical and horizontal kinetic energies ($V^2/H^2$) can be measured from 5 to 25Hz and shows an abrupt transitionfrom 0.1 in the 5-10Hz band, to about 0.8 in the 15-25Hz band. These measured values are in sharp contrast with the theoretical prediction for equipartitioned elastic waves in a homogeneous half-space. To explain these observations, we have developed a theory of equipartition in a layered elastic half-space. Using a rigorous spectral decomposition of the elastic wave equation, we define equipartition as a white noise distributed over the complete set of eigenfunctions. The theory predicts that close to the resonance frequency of a low-velocity layer, the ratio between shear and compressional energies strongly decreases. Using a detailed model of the subsurface at PFO, this conterintuitive result is found to be in good qualitative and quantitative agreement with the observations

Low cost and state of the art methods to measure nitrous oxide emissions

This letter provides an overview of the available measurement techniques for nitrous oxide (N2O) flux measurement. It is presented to aid the choice of the most appropriate methods for different situations. Nitrous oxide is a very potent greenhouse gas; the effect of 1 kg of N2O is estimated to be equivalent to 300 kg of CO2. Emissions of N2O from the soil have a larger uncertainty compared to other greenhouse gases. Important reasons for this are low atmospheric concentration levels and enormous spatial and temporal variability. Traditionally such small increases are measured by chambers and analyzed by gas chromatography. Spatial and temporal resolution is poor, but costs are low. To detect emissions at the field scale and high temporal resolution, differences at tens of ppt levels need to be resolved. Reliable instruments are now available to measure N2O by a range of micrometeorological methods, but at high financial cost. Although chambers are effective in identifying processes and treatment effects and mitigation, the future lies with the more versatile high frequency and high sensitivity sensors

Observation of Equipartition of Seismic Waves

International audienceEquipartition is a first principle in wave transport, based on the tendency of multiple scattering to homogenize phase space. We report observations of this principle for seismic waves created by earthquakes in Mexico. We find qualitative agreement with an equipartition model that accounts for mode conversions at the Earth's surface

R&D on support to ITER safety assessment

After performing its first ITER safety assessment in 2002 on behalf of the French "Autorité de Sûreté Nucléaire (ASN)", the French "Institut de Radioprotection et de Sûreté Nucléaire (IRSN)" is now analysing the new ITER Fusion facility safety file. The operator delivered this file to the ASN as part of its request for a creation decree, legally necessary before building works can begin on the site. The IRSN first task in following ITER throughout its lifetime is to study the safety approach adopted by the operator and the associated issues. Such a challenging new technology calls for further in-house expertise and so in parallel a R&D program has been set up to support this safety assessment process, now and in the next years. Its main objectives are to identify the key parameters for mastering some risks (that would have been insufficiently justified by the operator) and to perform some verifications with methods and codes independent from the operator's ones. Priority has been given to four technical issues (others could be investigated in the future, like the behaviour of activated corrosion products). The first issue concerns the simulation of accident sequences with the help of the ASTEC European system code, developed by IRSN (jointly with its German counterpart, the GRS) for severe accidents in Pressurised Water Reactors. A preliminary analysis showed that most of its physical models are already applicable, e.g., for thermal-hydraulics in accidents caused by water or air ingress into the vacuum vessel (VV) or dust transport. Work has started in 2008 on some model adaptations, for instance oxidation of VV first wall materials by steam or air, and on validation on the ITER-specific ICE and LOVA experiments. Other model improvements are planned in the next years, as feedback from the work done for the other technical issues and from the code validation. The second issue concerns the risk of gas explosion due to concentrations of hydrogen and carbon monoxide in the ITER main volumes (VV but also the neighbouring volumes), produced by wall materials oxidation. A consistent program of modelling in the Computational Fluid Dynamics (CFD) TONUS IRSN code and of experiments in the TOSQAN (IRSN) and ENACEFF (CNRS/Orléans, France) facilities has been defined: inertising as means of mitigation, flammability limits, flame acceleration and transition to detonation, gas combustion. The third issue concerns the risk of dust explosion due to concentrations in the ITER volumes after remobilisation of dust deposits on walls. A consistent program of modelling in the CAST3M code (CEA), in collaboration with the Carthagene University (Spain), and of experiments in the BISE and TOSQAN IRSN facilities has been defined. The concerned phenomena are dust spatial distribution, remobilisation and entrainment, and explosion. The studies will also address the characterisation of dust and the control and mitigation processes. The fourth issue concerns the tritium behaviour. The theoretical analysis addresses its retention in the VV first walls, its chemistry in the gas phase during transport in the cooling circuits, and in the liquid phases during trapping in the neighbouring volumes or buildings. The efficiency of the diverse processes foreseen for detritiation, either in the VV or in the other rooms, in relation with the ventilation systems, is being also investigated. © 2008 Elsevier B.V. All rights reserved

Recent advances in ASTEC validation on circuit thermal-hydraulic and core degradation

Within the SARNET network of excellence in the 6th Framework Programme of the European Commission, the severe accident integral code ASTEC, jointly developed by IRSN (France) and GRS (Germany), has been validated against international experiments to evaluate the suitability and capability of new or improved models implemented in successive code versions up to V1.3rev2, delivered in December 2007. This paper focuses on the code applications concerning circuit thermal-hydraulics and core degradation to integral and separate-effect experiments: for the CESAR thermal-hydraulic module, BETHSY 9.1 b, PACTEL ISP 33 and T2.1, PMK2-SBLOCA, LOFT-LP-FP-2; for the DIVA core degradation module, CORA-13 and -W2, QUENCH-11 and -13, LOFT-LP-FP-2, Phébus FPT-4, FARO L14 and L28, LIVE-L1, OLHF-1, FOREVER EC2. Besides, the TMI-2 accident has been analyzed using the CESAR and DIVA modules in a coupling mode. The emphasis was put on the following new or improved models: i.e. in CESAR, reflooding of an intact core, condensation in the pressurizer, sub-critical break flow correlation, and new pressurizer spray model; in DIVA, corium behaviour in the lower head and lower head mechanical failure. For thermal-hydraulics in the circuits, good results have been obtained with ASTEC on the three integral experiments that cover various thermal-hydraulic flow regimes: LOFT-LP-FP-2 in Western PWR geometry and the two PACTEL experiments in VVER-440 geometry. These good results have been confirmed by the validation done on several BETHSY integral tests. For core degradation, the ASTEC results are good for early-phase models of core heat-up, oxidation and hydrogen production (before any quenching phase) on different CORA and QUENCH experiments and on LOFT-LP-FP-2. For the in-vessel late-phase, the results can be considered as good regarding debris bed melting (Phébus FPT-4), corium fragmentation at slump into vessel lower plenum (FARO), molten pool behaviour in lower plenum (LIVE-L1), and vessel lower head mechanics (OLHF-1 and FOREVER EC2). Furthermore, the first two phases of the TMI-2 accident before core reflooding are very well calculated by ASTEC. The main remaining modelling weaknesses concern the reflooding of a degraded core and the corresponding hydrogen production. The implementation of detailed magma 2D relocation models in the new series of ASTEC V2 versions (the first one being released mid-2009) will allow a more realistic simulation of late phase phenomena up to the failure of the lower head. © 2009 Elsevier Ltd. All rights reserved