Results of the BiPo-1 prototype for radiopurity measurements for the SuperNEMO double beta decay source foils

The development of BiPo detectors is dedicated to the measurement of extremely high radiopurity in $^{208}$Tl and $^{214}$Bi for the SuperNEMO double beta decay source foils. A modular prototype, called BiPo-1, with 0.8 $m^2$ of sensitive surface area, has been running in the Modane Underground Laboratory since February, 2008. The goal of BiPo-1 is to measure the different components of the background and in particular the surface radiopurity of the plastic scintillators that make up the detector. The first phase of data collection has been dedicated to the measurement of the radiopurity in $^{208}$Tl. After more than one year of background measurement, a surface activity of the scintillators of $\mathcal{A}$($^{208}$Tl) $=$ 1.5 $\mu$Bq/m$^2$ is reported here. Given this level of background, a larger BiPo detector having 12 m$^2$ of active surface area, is able to qualify the radiopurity of the SuperNEMO selenium double beta decay foils with the required sensitivity of $\mathcal{A}$($^{208}$Tl) $<$ 2 $\mu$Bq/kg (90% C.L.) with a six month measurement.Comment: 24 pages, submitted to N.I.M.

Spectral modeling of scintillator for the NEMO-3 and SuperNEMO detectors

We have constructed a GEANT4-based detailed software model of photon transport in plastic scintillator blocks and have used it to study the NEMO-3 and SuperNEMO calorimeters employed in experiments designed to search for neutrinoless double beta decay. We compare our simulations to measurements using conversion electrons from a calibration source of $\rm ^{207}Bi$ and show that the agreement is improved if wavelength-dependent properties of the calorimeter are taken into account. In this article, we briefly describe our modeling approach and results of our studies.Comment: 16 pages, 10 figure

On the mechanisms governing gas penetration into a tokamak plasma during a massive gas injection

A new 1D radial fluid code, IMAGINE, is used to simulate the penetration of gas into a tokamak plasma during a massive gas injection (MGI). The main result is that the gas is in general strongly braked as it reaches the plasma, due to mechanisms related to charge exchange and (to a smaller extent) recombination. As a result, only a fraction of the gas penetrates into the plasma. Also, a shock wave is created in the gas which propagates away from the plasma, braking and compressing the incoming gas. Simulation results are quantitatively consistent, at least in terms of orders of magnitude, with experimental data for a D 2 MGI into a JET Ohmic plasma. Simulations of MGI into the background plasma surrounding a runaway electron beam show that if the background electron density is too high, the gas may not penetrate, suggesting a possible explanation for the recent results of Reux et al in JET (2015 Nucl. Fusion 55 093013)

The Physics of the B Factories

This work is on the Physics of the B Factories. Part A of this book contains a brief description of the SLAC and KEK B Factories as well as their detectors, BaBar and Belle, and data taking related issues. Part B discusses tools and methods used by the experiments in order to obtain results. The results themselves can be found in Part C

Nanocrystalline diamond films grown at very low substrate temperature using a distributed antenna array microwave process: Towards polymeric substrate coating

International audienc

The influence of the cube component on the mechanical behaviour of copper polycrystalline samples in tension

International audienceCopper tensile samples were prepared by various thermomechanical treatments (rolling and annealing) producing different initial textures, characterized mainly by an increasing Cube component. These samples were characterized microstructurally (orientation, grain boundary and grain size distributions) and mechanically (tensile stress-strain curves, hardness, dislocation density). It is found that an increase of the Cube percentage leads to an increase of the initial yield stress and to a decrease of the hardening rate at high strains. The macroscopic mechanical behaviour is compared with simulations performed with a simple Taylor type model including anisotropic plastic behaviour and dislocation-based constitutive equations. We show that the proposed modeling allows to reproduce all experimental curves with a limited number of adjusted parameters and that dynamic softening is more active in the Cube orientation than in any other present orientation. This is also confirmed by the EBSD and X-Ray data. As a result, the Cube orientation is shown to be softer in terms of texture and hardening rate. The opposite strengthening effect observed on the initial yield stress is shown to be due to heterogeneous grain size distributions resulting from complex recrystallization mechanisms

Phenomenological study of the densification behavior of Aluminum–Nickel powder mixtures during cold isostatic pressing and differential hydrostatic extrusion

Compaction and extrusion of Al and Ni powder mixtures were performed by cold isostatic pressing (CIP) and differential hydrostatic extrusion (DHE) at room temperature. Relative density and Vickers hardness were determined as a function of the compaction pressure, showing a significant increase in the density with increasing Al content for comparable pressing conditions; at the same time, the addition of a very small quantity of Al in Ni decreases the hardness significantly. Williamson–Hall method was applied to determine microstrains evolution during CIP, and X-ray diffraction (XRD) analyses were performed to investigate texture evolution during DHE. Finally Archimedes' principle was used to estimate the densification occurring during DHE

Application de la méthode de Laue refocalisée à haute énergie à l'étude des mécanismes de recristallisation après déformation à froid de métaux CFC

In order to determine the kinetics of recystallization process, the Laue diffraction method is apllied here on cold rolled and recrystallized copper materials. Firts, the results obtained from reflexion X-ray diffraction texture measurements are presented. It is shown that the both techniques are complementar, and that the transmission Laue method presents some advantadges. Some previous hypotheses are verified in this work. Especially, the Cube orientation $\{100\}$ loses during recrystallization its advantadge of growth, which implies the development of a mixed “deformed-recrystallized” texture at the end of the process. The nucleation step determines the final recrystallized texture.La méthode de Laue haute énergie est appliquée ici dans le but de déterminer les cinétiques de recristallisation de matériaux cuivre après laminages à froid et recuits interrompus. Après présentation des résultats obtenus par mesures classiques en réflexion, une comparaison est effectuée entre les deux techniques permettant de rendre compte des avantages certains qu'offrent des mesures en transmission et de la complémentarité des deux techniques utilisées. Quelques hypothèses sur les mécanismes régissant le processus de recristallisation sont ainsi vérifiées. Au tout début du processus de recristallisation, il a clairement été mis en évidence une perte de l'avantage de croissance des germes d'orientation Cube $\{100\}$ au profit des composantes constituant la texture de déformation. Dans ce type de processus, n'est préférentielle que l'étape de germination, dans le sens où elle détermine la texture finale après recristallisation

Extrusion-activated thermal explosion applied to intermetallics processing

International audienceThe present study deals with synthesizing the NiAl compound through the thermal-explosion route akin to self-propagating high-temperature synthesis under the novel circumstance of extrusion-induced mechanical activation. Either route has the potential for addressing the intermetallics processing cost problem and both reactions may alike be significantly enhanced by prior activation. Reactant powders were homogeneously mixed and precompacted by cold isostatic pressing (CIP) at 800 MPa. Hydrostatic extrusion was performed with a lower-chamber pressure fixed at 50 MPa and an upper-chamber pressure of 1.4 GPa, hence yielding a fully dense Ni+Al mixture, maximizing the contact areas between reactants and enhancing the specific surfaces of Al without such a grain refinement as with mechanical activation by ball milling. After heating up to 550 °C with a rate of 10 °C/min, uniquely CIPed samples did not react, whereas those subsequently extruded did react in the thermal-explosion mode with temperature overstepping 1084 °C