Excitations in confined helium

We design models for helium in matrices like aerogel, Vycor or Geltech from a manifestly microscopic point of view. For that purpose, we calculate the dynamic structure function of 4He on Si substrates and between two Si walls as a function of energy, momentum transfer, and the scattering angle. The angle--averaged results are in good agreement with the neutron scattering data; the remaining differences can be attributed to the simplified model used here for the complex pore structure of the materials. A focus of the present work is the detailed identification of coexisting layer modes and bulk--like excitations, and, in the case of thick films, ripplon excitations. Involving essentially two--dimensional motion of atoms, the layer modes are sensitive to the scattering angle.Comment: Phys. Rev. B (2003, in press

Epitaxial MgB2 thin films on ZrB2 buffer layers: structural characterization by synchrotron radiation

Structural and superconducting properties of magnesium diboride thin films grown by pulsed laser deposition on zirconium diboride buffer layers were studied. We demonstrate that the ZrB2 layer is compatible with the MgB2 two step deposition process. Synchrotron radiation measurements, in particular anomalous diffraction measurements, allowed to separate MgB2 peaks from ZrB2 ones and revealed that both layers have a single in plane orientation with a sharp interface between them. Moreover, the buffer layer avoids oxygen contamination from the sapphire substrate. The critical temperature of this film is near 37.6 K and the upper critical field measured at Grenoble High Magnetic Field Laboratory up to 20.3 T is comparable with the highest ones reported in literature.Comment: 14 pages, 8 figures, submitted to Supercond. Sci. and Techno

Proceedings of the third French-Ukrainian workshop on the instrumentation developments for HEP

The reports collected in these proceedings have been presented in the third French-Ukrainian workshop on the instrumentation developments for high-energy physics held at LAL, Orsay on October 15-16. The workshop was conducted in the scope of the IDEATE International Associated Laboratory (LIA). Joint developments between French and Ukrainian laboratories and universities as well as new proposals have been discussed. The main topics of the papers presented in the Proceedings are developments for accelerator and beam monitoring, detector developments, joint developments for large-scale high-energy and astroparticle physics projects, medical applications.Comment: 3rd French-Ukrainian workshop on the instrumentation developments for High Energy Physics, October 15-16, 2015, LAL, Orsay, France, 94 page

Purification of molybdenum oxide, growth and characterization of medium size zinc molybdate crystals for the LUMINEU program

The LUMINEU program aims at performing a pilot experiment on neutrinoless double beta decay of 100Mo using radiopure ZnMoO4 crystals operated as scintillating bolometers. Growth of high quality radiopure crystals is a complex task, since there are no commercially available molybdenum compounds with the required levels of purity and radioactive contamination. This paper discusses approaches to purify molybdenum and synthesize compound for high quality radiopure ZnMoO4 crystal growth. A combination of a double sublimation (with addition of zinc molybdate) with subsequent recrystallization in aqueous solutions (using zinc molybdate as a collector) was used. Zinc molybdate crystals up to 1.5 kg were grown by the low-thermal-gradient Czochralski technique, their optical, luminescent, diamagnetic, thermal and bolometric properties were tested.Comment: Contribution to Proc. of Int. Workshop on Radiopure Scintillators RPSCINT 2013, 17-20 September 2013, Kyiv, Ukraine; to be published in EPJ Web of Conferences; expected to be online in January 2014; 6 pages, 6 figures, and 3 table

Development of 100^{100}Mo-containing scintillating bolometers for a high-sensitivity neutrinoless double-beta decay search

We report recent achievements in the development of scintillating bolometers to search for neutrinoless double-beta decay of $^{100}$Mo. The presented results have been obtained in the framework of the LUMINEU, LUCIFER and EDELWEISS collaborations, and are now part of the R\&D activities towards CUPID (CUORE Update with Particle IDentification), a proposed next-generation double-beta decay experiment based on the CUORE experience. We have developed a technology for the production of large mass ($\sim$1 kg), high optical quality, radiopure zinc and lithium molybdate crystal scintillators (ZnMoO$_4$ and Li$_2$MoO$_4$, respectively) from deeply purified natural and $^{100}$Mo-enriched molybdenum. The procedure is applied for a routine production of enriched crystals. Furthermore, the technology of a single detector module consisting of a large-volume ($\sim 100$~cm$^3$) Zn$^{100}$MoO$_4$ and Li$_2$$^{100}$MoO$_4$ scintillating bolometer has been established, demonstrating performance and radiopurity that are close to satisfy the demands of CUPID. In particular, the FWHM energy resolution of the detectors at 2615 keV --- near the $Q$-value of the double-beta transition of $^{100}$Mo (3034~keV) --- is $\approx$ 4--10~keV. The achieved rejection of $\alpha$-induced dominant background above 2.6~MeV is at the level of more than 99.9\%. The bulk activity of $^{232}$Th ($^{228}$Th) and $^{226}$Ra in the crystals is below 10 $\mu$Bq/kg. Both crystallization and detector technologies favor Li$_2$MoO$_4$, which was selected as a main element for the realization of a CUPID demonstrator (CUPID-0/Mo) with $\sim$7 kg of $^{100}$Mo

Scintillating bolometers based on ZnMoO4 and Zn100MoO4 crystals to search for 0ν2β decay of 100Mo (LUMINEU project): first tests at the Modane Underground Laboratory

The technology of scintillating bolometers based on zinc molybdate (ZnMoO4) crystals is under development within the LUMINEU project to search for decay of 100Mo with the goal to set the basis for large scale experiments capable to explore the inverted hierarchy region of the neutrino mass pattern. Advanced ZnMoO4 crystal scintillators with mass of ∼0.3 kg were developed and Zn100MoO4 crystal from enriched 100Mo was produced for the first time by using the low-thermal-gradient Czochralski technique. One ZnMoO4 scintillator and two samples (59 g and 63 g) cut from the enriched boule were tested aboveground at milli-Kelvin temperature as scintillating bolometers showing a high detection performance. The first results of the low background measurements with three ZnMoO4 and two enriched detectors installed in the EDELWEISS set-up at the Modane Underground Laboratory (France) are presented

Direct Hybridization Fuel Cell – Ultracapacitors

International audienceIt is now well recognized that highly dynamic power demands accelerate the ageing of a fuel cell. A solution is to hybridize it with an electrochemical storage device (ultracapacitors, Li-ion battery...). Whatever the technique implemented to manage energy, the hybridization principle forces the storage device to take in charge the rapid power changes to protect the fuel cell. Several electrical architectures are possible to interconnect the fuel cell and the storage device: indirect hybridization via power converters, or direct hybridization without power converters. The work here focuses on direct hybridization between a fuel cell and ultracapacitors. Classically, this kind of connection concerns the hybridization of a fuel cell stack with an ultracapacitors' pack. The authors here investigate another rather original option by implementing this hybridization at the scale of each cell of a fuel cell stack. In this approach, each elementary ultracapacitor can be connected either to one cell or to two cells. Before applying the concept to a real fuel cell stack (the final objective), the authors studied the concepts with single cells. This paper is going to present the intensive experimental works achieved to apprehend the principles. Static and dynamics properties of such hybridization are analyzed and modeled

Comparison between global chemistry transport model results and Measurement of Ozone and Water Vapor by Airbus In-Service Aircraft (MOZAIC) data

International audienceOzone distributions from state-of-the-art global three-dimensional chemistry transport models are compared to O:• data collected on Airbus A340 passenger aircraft as part of the Measurement of Ozone and Water Vapor by Airbus In-Service Aircraft (MOZAIC) project. The model results are compared to monthly averaged data at cruise altitudes in the upper troposphere and lower stratosphere and monthly averaged vertical profiles collected over particular cities during takeoff and landing. The models generally show good agreement with the data in regions which have previously been well documented and where the meteorology is well understood/captured by meteorological models (e.g., over Europe). However, in the upper troposphere and lower stratosphere, models often fail to capture sharp gradients across the tropopause and from the subtropics to the tropics. In some models, this is related to deficiencies in model transport schemes and upper boundary conditions. Also, regions of the globe where our understanding of meteorology is poorer and emissions are less well known (e.g., tropics, continental Africa, Asia, and South America) are not simulated as well by all models. At particular measurement locations, it is apparent that emission inventories used by some global models underestimate emissions in certain regions (e.g., over southern Asia) or have incorrect seasonal variations (e.g., biomass burning over South America). Deficiencies in chemical schemes may also explain differences between models and the data