Spiral spin-liquid and the emergence of a vortex-like state in MnSc2_2S4_4

Spirals and helices are common motifs of long-range order in magnetic solids, and they may also be organized into more complex emergent structures such as magnetic skyrmions and vortices. A new type of spiral state, the spiral spin-liquid, in which spins fluctuate collectively as spirals, has recently been predicted to exist. Here, using neutron scattering techniques, we experimentally prove the existence of a spiral spin-liquid in MnSc$_2$S$_4$ by directly observing the 'spiral surface' - a continuous surface of spiral propagation vectors in reciprocal space. We elucidate the multi-step ordering behavior of the spiral spin-liquid, and discover a vortex-like triple-q phase on application of a magnetic field. Our results prove the effectiveness of the $J_1$-$J_2$ Hamiltonian on the diamond lattice as a model for the spiral spin-liquid state in MnSc$_2$S$_4$, and also demonstrate a new way to realize a magnetic vortex lattice.Comment: 10 pages, 11 figure

Performance of LHC Main Dipoles for Beam Operation

At present about 90% of the main dipoles for the LHC have been manufactured and one of the three cold mass assemblers has already completed the production. 85% of the 1232 dipoles needed for the tunnel have been tested and accepted. In this paper we mainly deal with the performance results: the quench behaviour, the magnetic field quality, the electrical integrity quality and the geometry features will be summarized

Chapter 11: 11 T dipole and new connection cryostat for the dispersion suppressor collimators

In Run 3 the intensity of the ion beams (usually Pb ions) for ion–ion collisions is planned to be increased by a factor of three: from 40 × 109 to 120 × 109 circulating particles. This intensity increase will amplify the losses in the cold zone at P2 and P7 and may drive the beam induced heat losses in the main dipoles in the dispersion suppressor (DS) region above the quench limit. To avoid limiting the machine performance during ion operation due to this effect, various countermeasures have been studied, and the solution chosen was to intercept these diffractive losses via warm absorbers, so-called TCLDs (Target Collimator Long Dispersion) suppressors, left and right of the LHC interaction points P2 and P7

Finite Element Analysis of the Mechanical Conditions of the Nb3_3Sn Cable of the 11 T Dipole Magnet During Operation

The development of the 11 T Dipole for the Dispersion Suppressor Collimators (DS11T) for the HiLumi LHC Project at CERN is nearly completed for the RRP conductor route. The DS11T magnet has a cosine theta 60-mm bore design with a removable pole, 56 turns, five wedges, and six coil blocks per quadrant. The mechanical behavior of the magnet is critical for its performance. Until now, finite element analysis (FEA) was based on simplified models in which the coils were homogeneous bodies characterized by smeared properties to represent the conductor–insulation composite. Since the performance of Nb$_3$Sn superconductor is sensitive to the mechanical strain on the A15-lattice and linked to the strain in the cable, a new approach is considered, involving the separation of the cable and insulation matrix. In this paper, FEA is used to compute strain and stress in the cable in a cross section of the magnet in its straight part. A comparison is made between the single-cable model and the formerly used coil-block model. Two different mechanical structures are used for the short model program of the DS11T, hosting either one or two apertures (also called 1in1 and 2in1). The impact of these two structures on the loading conditions of the cable is presented. Several model magnets have been built and tested. The expected stresses and strains for each model are summarized and discussed using the most recent finite element model

Photocatalyzed Cu-based ATRP involving an oxidative quenching mechanism under visible light

International audienceA new type of photocatalyzed Cu-based atom transfer radical polymerization (ATRP) is described, involving directly the light absorption of the activator form of the copper complex Cu(I). The selected catalyst was bis(1,10-phenanthroline)copper(I), Cu(phen)2+, due to its intense absorption in the visible domain, which permitted to use very soft irradiation conditions, consisting of a simple household blue LED at 0.9 W. An excellent control over the polymerization of methyl methacrylate (MMA) in dimethylformamide (DMF) was observed under irradiation in these conditions, using ethyl α-bromophenylacetate (EBPA) as the initiator, with polydispersity indexes (PDI) as low as 1.10 while using low catalyst content (80 ppm). The proposed mechanism implies first the formation under irradiation of the excited state of the activator form of the complex Cu(I)*. It can then rapidly undergo the oxidative quenching of the alkyl bromide, which results in its conversion into the deactivator form of the complex Cu(II)–Br along with the generation of a propagating radical. The setting up of the ATRP equilibrium ensues. Additionally, it was possible to complete the catalysis mechanism by adding triethylamine (TEA), which permitted a faster polymerization, thanks to a faster regeneration of the activator Cu(I). An excellent control over the polymerization was also observed in the presence of TEA, with PDI as low as 1.06. The addition of TEA allowed also to use a catalyst loading as low as 20 ppm, while maintaining a good controllability

Association of helicopter transportation and improved mortality for patients with major trauma in the northern French Alps trauma system: an observational study based on the TRENAU registry.

Prompt prehospital triage and transportation are essential in an organised trauma system. The benefits of helicopter transportation on mortality in a physician-staffed pre-hospital trauma system remains unknown. The aim of the study was to assess the impact of helicopter transportation on mortality and prehospital triage. Data collection was based on trauma registry for all consecutive major trauma patients transported by helicopter or ground ambulance in the Northern French Alps Trauma system between 2009 and 2017. The primary endpoint was in-hospital death. We performed multivariate logistic regression to compare death between helicopter and ground ambulance. Overall, 9458 major trauma patients were included. 37% (n = 3524) were transported by helicopter, and 56% (n = 5253) by ground ambulance. Prehospital time from the first call to the arrival at hospital was longer in the helicopter group compared to the ground ambulance group, respectively median time 95 [72-124] minutes and 85 [63-113] minutes (P < 0.001). Median transport time was similar between groups, 20 min [13-30] for helicopter and 21 min [14-32] for ground ambulance. Using multivariate logistic regression, helicopter was associated with reduced mortality compared to ground ambulance (adjusted OR 0.70; 95% CI, 0.53-0.92; P = 0.01) and with reduced undertriage (OR 0.69 95% CI, 0.60-0.80; P < 0.001). Helicopter was associated with reduced in-hospital death and undertriage by one third. It did not decrease prehospital and transport times in a system with the same crew using both helicopter or ground ambulance. The mortality and undertriage benefits observed suggest that the helicopter is the proper mode for long-distant transport to a regional trauma centre

Mechanical Properties of the HL-LHC 11 T Nb3SnNb_3Sn Magnet Constituent Materials

Abstract: A test campaign was launched to determine the mechanical properties of the High Luminosity-Large Hadron Collider (HL-LHC) 11 T $Nb_3Sn$ magnet components. The results can be used to accurately represent the mechanical properties in finite element models that predict the stress and strain distribution in these magnets. Particular attention is paid to anisotropic mechanical behavior of the different magnet materials. Static and dynamic test methods have been applied for determining elastic materials' behavior, and highly accurate Young's moduli are obtained with the nondestructive dynamic methods resonance and impulse excitation at ambient temperature and during in situ heat cycles

Efficient blue green organic light-emitting devices based on a monofluorinated heteroleptic iridium (III) complex

International audienceTwo heteroleptic iridium complexes were synthesized and their photophysical properties studied. The two complexes vary by their ancillary ligand that is respectively acetylacetone (acac) or dibenzoylmethane (dbm). Interestingly, only the acac-based complex proved to be highly emissive and electroluminescent devices were only fabricated with this complex. In order to determine the emissive properties of this new complex, comparison with complexes previously reported in the literature was established

Magnetic measurements and analysis of the first 11-T Nb3_3 Sn 2-in-1 model for HL-LHC

In the framework of the High-Luminosity upgrade of the Large Hadron Collider, the design and development of new magnets, relying on Nb$_{3}$Sn superconducting cables, is progressing. In particular, a double-aperture dipole, with a bore diameter of 60 mm and a central field of 11 T, is required for the replacement of some Nb-Ti dipoles in the dispersion suppressor areas. The new magnets must comply with the specifications of the machine in terms of reliability and field quality. An intense short-model campaign was launched in order to validate the design choices. Various single-aperture models have been built and tested. Recently, the first 2-in-1 model has been produced by assembling the collared coils already tested in the single-aperture configuration. This paper presents the analysis of the magnetic measurements on the first 2-m-long, double-aperture demonstrator built and tested at CERN. The geometrical field multipoles, the iron saturation effects, the magnetic cross-talk as well as the effects of persistent currents are presented. The experimental data are compared with the magnetic calculations using the CERN field computation program ROXIE and are discussed in view of the construction of the full-length magnets