POLAREX Study of polarized exotic nuclei at millikelvin temperatures

POLAREX (POLARization of EXotic nuclei) is a new facility for the study of nuclear magnetic moments and decay modes of exotic nuclei using the established On-Line Nuclear Orientation (OLNO) method. A radioactive beam of interest is implanted into a ferromagnetic host foil held at a temperature of order 10mK in a ³He - ⁴He dilution refrigerator. The foil is magnetized by an applied magnetic field and the nuclear spins become polarized through the internal hyperfine field. The angular distribution of decay products from the polarized sample is measured. Accurate values of nuclear moment are obtained by NMR. The new facility will have access to neutron-rich nuclides produced at the ALTO facility (Linear Accelerator at Orsay Tandem) by fission induced by electrons from the linear electron accelerator. Basic concepts and initial tests are outlined.     

Obituary Gilbert Grynberg (1948-2003)

We mourn the death of Professor Dr. Gilbert Grynberg, April 17, 1948 - January 27, 2003. We have lost an excellent and highly esteemed scientist, an outstanding character and a good friend. He has been a very active colleague in the merger of Zeitschrift für Physik and Journal de Physique in the early days. As one of the Co-Editors-in-Chief of The European Physical Journal D, from its start, he has formed the scienti.c standards of EPJ. Untiringly he has served our Journal with greatest dedication. We are grateful that he has been with us. The editorial board and o.ce of EPJ B Siegfried Grossmann, Denis Jérome, Antonio Paoletti     

Basic function method A new numerical method on unstructured grids

A new numerical method-basic function method is proposed. This method can directly discrete differential operators on unstructured grids. By using the expansion of basic function to approach the exact function, the central and upwind schemes of derivative are constructed. By using the polynomial as basic function, applying the technique of flux splitting method and the combination of central and upwind schemes, the non-physical fluctuation near the shock wave is suppressed. The first-order basic function scheme of polynomial type for solving inviscid compressible flow numerically is constructed in this paper. Several numerical results of many typical examples for one-, two- and three-dimensional inviscid compressible steady flow illustrate that it is a new scheme with high accuracy and high resolution for shock wave. Especially, combining with the adaptive remeshing technique, the satisfactory results can be obtained by these schemes.     

Birefringence of interferential mirrors at normal incidence Experimental and computational study

In this paper we present a review of the existing data on interferential mirror birefringence. We also report new measurements of two sets of mirrors that confirm that mirror phase retardation per reflection decreases when mirror reflectivity increases. We finally developed a computational code to calculate the expected phase retardation per reflection as a function of the total number of layers constituting the mirror. Different cases have been studied and we have compared computational results with the trend of the experimental data. Our study indicates that the origin of the mirror intrinsic birefringence can be ascribed to the reflecting layers close to the substrate.     

Double-Delta Potentials: One Dimensional Scattering The Casimir Effect and Kink Fluctuations

The path is explored between one-dimensional scattering through Dirac-δ walls and one-dimensional quantum field theories defined on a finite length interval with Dirichlet boundary conditions. It is found that two δ’s are related to the Casimir effect whereas two δ’s plus the first transparent P?sch-Teller well arise in the context of the sine-Gordon kink fluctuations, both phenomena subjected to Dirichlet boundary conditions. One or two delta wells will be also explored in order to describe absorbent plates, even though the wells lead to non unitary Quantum Field Theories.     

Amorphous carbon and carbonaceous materials in space I.—Laboratory measurements

Summary We present here the most recent measurements (UV and Raman spectroscopy) carried out on carbonaceous materials candidates as cosmic dust. To speed up publication, the proofs were not sent to the authors and were supervised by the scientific Committee.     

Boson description of nuclear collective motion II. Application to octupole vibration

As the first part of the series on the application of the boson expansion method to the nuclear collective motion, the method of Kishimoto and Tamura is illustrated by taking a simple case of boson expansion up to second order. By taking into account the effect of particle channel by the projection technique, the lowest mode is shown to have the same property as the RPA phonon.     

Nonlinear elasticity of composite materials Landau coefficients in dispersions of spherical and cylindrical inclusions

We investigate the elastic properties of model composites, consisting in a dispersion of nonlinear (spherical or cylindrical) inhomogeneities into a linear solid matrix. Both phases are considered isotropic. Under the simplifying hypotheses of small deformation for the material body and of small volume fraction of the embedded phase, we develop a homogenization procedure based on the Eshelby theory, aimed at describing nonlinear features. We obtain the bulk and shear moduli and Landau coefficients of the overall material in terms of the elastic behavior of the constituents and of their volume fractions. The mixing laws for the nonlinear properties describe a complex scenario where possible strong amplifications of the nonlinearities may arise in some given conditions.     

TSS core equipment I.—Electrodynamic package and rationale for system electrodynamic analysis

Summary The first Tethered-Satellite System (TSS-1) Electrodynamic mission has been launched aboard the Space Shuttle STS-46 on July 31, 1992, as a joint mission between the United States and Italy. A 500 kg, spherical Satellite (1.6 m diameter), attached to the Orbiter by a thin (0.24 cm), conducting, insulated wire (Tether), has been reeled upwards from the Orbiter payload bay to a distance of 256 m, rather than the expected 20 km, when the Shuttle was at a projected altitude of 300 km. ASI, the Italian Space Agency, had the responsibility for developing the reusable Satellite, while NASA had the responsibility for developing the Deployer system and the Tether, integrating the payload and providing transportation into space. One of the main scientific goals of this first mission is to demonstrate the possibility of energy conversion from mechanical to electrical by using a long Tether orbiting through the Earth's magnetic field. ASI designed and developed an active experiment, referred to as Core Equipment, in order to carry out this demonstration, and to support all the scientific investigations related to the study of the TSS electrodynamic interactions with the Earth's ionosphere. The experiment uses two Electron Generator Assemblies (EGAs), located on the Orbiter, to re-emit into the ionosphere, as an electron beam, the electrons collected on the Satellite from the ionosphere. Other instruments provide current, voltage, and ambient pressure measurements, and allow, via a series of switches, different electrical configurations of the TSS. The Core Equipment was innovative for space experiments in general and Shuttle experiments in particular. In fact, it was the first flight in which the Shuttle has been used as an integral part of the experiment and not only as an observing platform. It was the first mission with an integrated approach to science, will all the instrumentation and their operative modes selected to characterize the electric properties of the TSS.     

The ferroelectric phase transition in LiTaO3 studied by neutron scattering I. The Long-Range Order

Elastic neutron scattering from two reflections has been studied versus temperature, and the temperature dependence of the ferroelectric polarizationP(T) has been deduced. Neart _c =601°C the dependence is found to be classical: (T _c –T)^1/2. The study supports a model where the ferroelectric transition is accompanied by an order-disorder transition of the lithium ions.     

A study on forest fire automatic detection systems I.—Smoke plume model

Summary A mathematical model of the smoke plume produced by a forest fire is described. The model serves to obtain an estimate of the infra-red and optical signatures of the plume, taking into account several factors, such as fuel composition, combustion process characteristics, smoke diffusion, and the optical properties of the smoke and surrounding environment. The results of this model are used in a further paper to analyse the features and performances of automatic detection systems.     

Parametric study of horizontally vibrated grain packings Comparison between Discrete Element Method and experimental results

Numerical and experimental studies have been undertaken to analyze three parameters controlling the compaction of granular media submitted to sinusoidal horizontal vibrations. We have characterized the influence of the dimensionless acceleration G \Gamma , the geometry of the container and the friction coefficients on the grain velocities and on the packing densities. Above a critical acceleration G_crit \Gamma_{{\rm crit}}^{} , the velocities increases with G \Gamma . For low values of G \Gamma , the surface layers are compacted, whereas the bottom layers remain at their initial density. For high values of G \Gamma , the bottom layers get compacted, the surface layers are fluidized so that the bulk dynamic and relaxed densities decreased. In the same way, the effect of the dimensions of the container and of the friction coefficients on the packing properties has been studied for given heights of sand, acceleration and frequency. It has been shown that the influence of the two last parameters is similar to that of acceleration. The numerical results given by the Discrete Element Method appear to be in good agreement with experimental results.     

Neutrino quasielastic scattering on nuclear targets Parametrizing transverse enhancement (meson exchange currents)

We present a parametrization of the observed enhancement in the transverse electron quasielastic (QE) response function for nucleons bound in carbon as a function of the square of the four momentum transfer (Q ²) in terms of a correction to the magnetic form factors of bound nucleons. The parametrization should also be applicable to the transverse cross section in neutrino scattering. If the transverse enhancement originates from meson exchange currents (MEC), then it is theoretically expected that any enhancement in the longitudinal or axial contributions is small. We present the predictions of the “Transverse Enhancement” model (which is based on electron scattering data only) for the ν _μ , [`(n)]_m\bar{\nu}_{\mu} differential and total QE cross sections for nucleons bound in carbon. The Q ² dependence of the transverse enhancement is observed to resolve much of the long standing discrepancy in the QE total cross sections and differential distributions between low energy and high energy neutrino experiments on nuclear targets.     

On nuclear states of [`(K)] \bar K mesons

The search for nuclear states of $ \bar K $ \bar K mesons poses interesting problems for the nuclear and low energy hadron physics: the behavior of tightly bound nuclear systems with strongly correlated impurities, the new kind of binding mechanisms and the extension of effective low energy theories to the strange sector. These problems are briefly presented and a method of variational calculation of the binding energies is discussed.     

Heterogeneous diffuse interfaces: A new mechanism for arrested coarsening in binary mixtures Heterogeneous diffuse interfaces

We discuss the dynamics of binary fluid mixtures in which surface tension density is allowed to become locally negative within the interface, while still preserving positivity of the overall surface tension (heterogeneous diffuse interface). Numerical simulations of two-dimensional Ginzburg-Landau phase field equations implementing such mechanism and including hydrodynamic motion, show evidence of dynamically arrested domain coarsening. Under specific conditions on the functional form of the surface tension density, dynamical arrest can be interpreted in terms of the collective dynamics of metastable, non-linear excitations of the density field, named compactons, as they are localized to finite-size regions of configuration space and strictly zero elsewhere. Aside from compactons, the heterogeneous diffuse interface scenario appears to provide a robust mechanism for the interpretation of many aspects of soft-glassy behaviour in binary fluid mixtures.     

Neutral pion production in the threshold region Conclusive Symposium of the Collaborative Research Centre 443

We give an overview of the physics motivation and evolution of the neutral pion photoproduction measurements in the threshold region conducted in the A2 collaboration at MAMI. The latest two experiments have been performed with the almost 4π Crystal Ball detector. The first was with a linearly polarized photon beam and unpolarized liquid-hydrogen target. The data analysis is now complete and the linearly polarized beam asymmetry along with differential cross sections provide the most stringent test to date of the predictions of Chiral Perturbation Theory and its energy region of convergence. More recently a measurement was performed using both circularly polarized photons and a transversely polarized butanol frozen-spin target, with the goal of extracting both the target and beam-target asymmetries. From these we intend to extract πN scattering sensitive information for the first time in photo-pion reactions. This will be used to test isospin conservation and further test dynamics of chiral symmetry breaking in QCD as calculated at low energies by Chiral Perturbation Theory.