The deep-sea hub of the ANTARES neutrino telescope

The ANTARES neutrino telescope, currently under construction at 2500 m depth off the French Mediterranean coast, will contain 12 detection lines, powered and read out through a deep-sea junction box (JB) hub. Electrical energy from the shore station is distributed through a transformer with multiple secondary windings and a plugboard with 16 deep sea-mateable electro-optic connectors. Connections are made to the JB outputs using manned or remotely operated submersible vehicles. The triply redundant power management and slow control system is based on two identical AC-powered systems, communicating with the shore through 160 Mb/s fibre G-links and a third battery-powered system using a slower link. We describe the power and slow control systems of the underwater hub

The effects of disk and dust structure on observed polarimetric images of protoplanetary disks

Imaging polarimetry is a powerful tool for imaging faint circumstellar material. For a correct analysis of observations we need to fully understand the effects of dust particle parameters, as well as the effects of the telescope, atmospheric seeing, and assumptions about the data reduction and processing of the observed signal. Here we study the major effects of dust particle structure, size-dependent grain settling, and instrumental properties. We performed radiative transfer modeling using different dust particle models and disk structures. To study the influence of seeing and telescope diffraction we ran the models through an instrument simulator for the ExPo dual-beam imaging polarimeter mounted at the 4.2m William Herschel Telescope (WHT). Particle shape and size have a strong influence on the brightness and detectability of the disks. In the simulated observations, the central resolution element also contains contributions from the inner regions of the protoplanetary disk besides the unpolarized central star. This causes the central resolution element to be polarized, making simple corrections for instrumental polarization difficult. This effect strongly depends on the spatial resolution, so adaptive optics systems are needed for proper polarization calibration. We find that the commonly employed homogeneous sphere model gives results that differ significantly from more realistic models. For a proper analysis of the wealth of data available now or in the near future, one must properly take the effects of particle types and disk structure into account. The observed signal depends strongly on the properties of these more realistic models, thus providing a potentially powerful diagnostic. We conclude that it is important to correctly understand telescope depolarization and calibration effects for a correct interpretation of the degree of polarization.Comment: Accepted for publication in A&

A New Strategy for Deep Wide-Field High Resolution Optical Imaging

We propose a new strategy for obtaining enhanced resolution (FWHM = 0.12 arcsec) deep optical images over a wide field of view. As is well known, this type of image quality can be obtained in principle simply by fast guiding on a small (D = 1.5m) telescope at a good site, but only for target objects which lie within a limited angular distance of a suitably bright guide star. For high altitude turbulence this 'isokinetic angle' is approximately 1 arcminute. With a 1 degree field say one would need to track and correct the motions of thousands of isokinetic patches, yet there are typically too few sufficiently bright guide stars to provide the necessary guiding information. Our proposed solution to these problems has two novel features. The first is to use orthogonal transfer charge-coupled device (OTCCD) technology to effectively implement a wide field 'rubber focal plane' detector composed of an array of cells which can be guided independently. The second is to combine measured motions of a set of guide stars made with an array of telescopes to provide the extra information needed to fully determine the deflection field. We discuss the performance, feasibility and design constraints on a system which would provide the collecting area equivalent to a single 9m telescope, a 1 degree square field and 0.12 arcsec FWHM image quality.Comment: 46 pages, 22 figures, submitted to PASP, a version with higher resolution images and other supplementary material can be found at http://www.ifa.hawaii.edu/~kaiser/wfhr

The first determination of Generalized Polarizabilities of the proton by a Virtual Compton Scattering experiment

Absolute differential cross sections for the reaction (e+p -> e+p+gamma) have been measured at a four-momentum transfer with virtuality Q^2=0.33 GeV^2 and polarization \epsilon = 0.62 in the range 33.6 to 111.5 MeV/c for the momentum of the outgoing photon in the photon-proton center of mass frame. The experiment has been performed with the high resolution spectrometers at the Mainz Microtron MAMI. From the photon angular distributions, two structure functions which are a linear combination of the generalized polarizabilities have been determined for the first time.Comment: 4 pages, 3 figure

Measurement of the Generalized Forward Spin Polarizabilities of the Neutron

The generalized forward spin polarizabilities $\gamma_0$ and $\delta_{LT}$ of the neutron have been extracted for the first time in a $Q^2$ range from 0.1 to 0.9 GeV$^2$. Since $\gamma_0$ is sensitive to nucleon resonances and $\delta_{LT}$ is insensitive to the $\Delta$ resonance, it is expected that the pair of forward spin polarizabilities should provide benchmark tests of the current understanding of the chiral dynamics of QCD. The new results on $\delta_{LT}$ show significant disagreement with Chiral Perturbation Theory calculations, while the data for $\gamma_0$ at low $Q^2$ are in good agreement with a next-to-lead order Relativistic Baryon Chiral Perturbation theory calculation. The data show good agreement with the phenomenological MAID model.Comment: 5 pages, 2 figures, corrected typo in author name, published in PR

Fréquence du syndrome d'hyperthermie maligne dans des populations porcines françaises; relation avec le développement musculaire

International audienc

The Q^2 evolution of the generalized Gerasimov-Drell-Hearn integral for the neutron using a He-3 target

We present data on the inclusive scattering of polarized electrons from a polarized He-3 target at energies from 0.862 to 5.06 GeV, obtained at a scattering angle of 15.5 degrees. Our data include measurements from the quasielastic peak, through the resonance region, to the beginning of the deep inelastic regime, and were used to determine the spin difference in the virtual photoabsorption cross section. We extract the extended Gerasimov-Drell-Hearn integral for the neutron in the range of 4-momentum transfer squared Q^2 of 0.1-0.9 GeV.Comment: 14 pages of text when TeXed in preprint format with figures embedded. RevTeX format. Three eps figure