La dynamique des lieux touristiques littoraux

La dynamique des lieux touristiques littorau

MADMAX Cryogenic Stability: Preliminary Design of the Macumba Demo-Coil for Physics

International audienceThe objective of the MADMAX project, led by the Max Planck Institute, is to detect axion dark matter with a mass of ∼100 µeV. To amplify the detection signal of the photons, induced by the axion conversion, the MADMAX dipole must produce ∼9 T within a 1.35 m aperture where a booster, the signal amplifier, is located. At the current stage of the project a demonstrator, Macumba, is needed for various reasons, i) to show that nominal current operation can be reached with MADMAX, ii) to practice coil fabrication, iii) to train the team that will be in charge of the MADMAX operation at DESY and iv) to start learning about the axion physics. Here is presented the design of the Macumba demonstrator magnet that targets operating conditions close to the final magnet in terms of loadline, mechanical constraints and heat generation. The structure and conductor of the demonstrator must be similar to a MADMAX coil to face the same fabrication issue as for MADMAX coils. This would allow improving the manufacturing procedures and tooling. In addition, Macumba magnet produces a physic-compatible magnetic field in an aperture able to host an R&D booster in preparation for the operation at DESY

Study of a CICC Copper Jacket Junction for MADMAX

International audienceFor the Magnetized Disc and Mirror Axion eXperiment (MADMAX) project (Caldwell et al. 2017), we need some junctions between the coil double pancakes and with the current leads. MADMAX coils are skateboard double pancakes (Caldwell et al. 2017) placed in a static superfluid helium bath. For the first mock-up coil, called MAdmax Coil for Quench Understanding (MACQU), the current lead junctions were based on the W7X box design, but we got some limitation in these boxes at 80% of the critical current due to bad current distribution. To avoid this issue, for the MADMAX junctions design, we tried the simplest solution for a copper jacket cable in conduit conductor that consists to directly solder both jackets together. We made some resistance measurements on the MACQU mock-up conductor, and we defined semi-analytic formulae to extrapolate the result to the MADMAX conductor

Sol-gel route: An original strategy to chemically stabilize proton exchange membranes for fuel cell

International audienceWe present the elaboration, via a Sol-Gel (SG) route, of a new generation of hybrid membranes for PEMFC applications, in order to improve their performances and durability. The strategy was to create, within a commercial sPEEK membrane, a reactive SG phase able to reduce the oxidative species generated during FC operation and to improve the proton conductivity. The SG content is adjusted by tuning the SG precursors/sPEEK ratio used for the impregnation step. Raman analyses show that a uniform distribution of the SG phase in the membrane section is obtained when NMR analyses demonstrate its high extent of condensation, and reveal the structuring effect of the sPEEK membrane on the SG phase at the nanoscale. The membranes exhibit a better liquid water uptake and proton conductivity than pristine sPEEK membrane up to a SG uptake of 18%, with a gas permeability slightly higher than sPEEK but still lower than the benchmark Nafion. H2O2 accelerated aging tests evidenced the ability of the SG phase to prevent the oxidative degradation of sPEEK. Finally, the FC operability tests showed better and more durable performances for the hybrid membranes, without any increase of the gas permeability during operation

Performance of a liquid argon electromagnetic calorimeter with a cylindrical accordion geometry

A Prototype of a lead liquid argon accordion calorimeter with two types of cylindrical geometry was constructed and equipped with high speed readout electronics. The energy resolution for electrons is 10%/square-root E (GeV) with a local constant term of 0.65%. The resolutions obtained for position and angular measurements are given