5 research outputs found
Structure from glass to melt: a case study along the MgSiO–CaSiO join using neutron and X-ray diffraction
No full textGlass and melt structures are inherently complex and disordered with significant changes expected to occur with temperature. In the present paper, a comparison of the structure of glasses and liquids along the MgSiO3–CaSiO3 join is carried out using neutron and X-ray diffraction (XRD). Empirical Potential Structure Refinement (EPSR) simulations were used to fit the experimental data. The average coordination number (CN) and site distribution is obtained for Mg and Ca showing distinct sites between the two cations and higher coordinated sites in the liquids. The major glass to melt modifications is observed at the scale of intermediate range order (IRO) by rearrangement of the (Ca,Mg)–Si and (Ca,Mg)–(Ca,Mg) connections. The structural evolution with temperature, especially concerning the cationic environments, illustrates the differences between glass and melt organization. These changes highlight the important contribution of cations to thermodynamical properties, diffusion and glass forming ability
Operation of a free-electron laser from the extreme ultraviolet to the water window
No full textWe report results on the performance of a free-electron laser operating at a wavelength of 13.7 nm where unprecedented peak and average powers for a coherent extreme-ultraviolet radiation source have been measured. In the saturation regime, the peak energy approached 170 J for individual pulses, and the average energy per pulse reached 70 J. The pulse duration was in the region of 10 fs, and peak powers of 10 GW were achieved. At a pulse repetition frequency of 700 pulses per second, the average extreme-ultraviolet power reached 20 mW. The output beam also contained a significant contribution from odd harmonics of approximately 0.6% and 0.03% for the 3rd (4.6 nm) and the 5th (2.75 nm) harmonics, respectively. At 2.75 nm the 5th harmonic of the radiation reaches deep into the water window, a wavelength range that is crucially important for the investigation of biological samples
Structural properties of molten dilute aluminium-transition metals
No full textInternational audienceThe short-range order in liquid binary Al-rich alloys (Al-Fe, Al-Ti) was studied by x-ray diffraction. The measurements were performed using a novel containerless technique which combines aerodynamic levitation with inductive heating. The average structure factors S(Q) have been determined for various temperatures and compositions in the stable liquid state. From S(Q), the pair correlation functions g(r), have been calculated. The first interatomic distance is nearly temperature-independent, whereas the first-shell coordination number decreases with increasing temperature for all the alloys investigated. For the Al-Fe alloys, room-temperature SEM studies show the formation of a microstructure, namely, the existence of AlFe inclusions in the Al matrix
The deuteron spin-dependent structure function g(1)(d) and its first moment
No full textAlexakhin VY, Alexandrov Y, Alexeev GD, et al. The deuteron spin-dependent structure function g(1)(d) and its first moment. Phys.Lett. B. 2007;647(1):8-17.We present a measurement of the deuteron spin-dependent structure function g(1)(d) based on the data collected by the COMPASS experiment at CERN during the years 2002-2004. The data provide an accurate evaluation for Gamma(d)(1), the first moment of g(1)(d) (x), and for the matrix element of the singlet axial current, a(0). The results of QCD fits in the next to leading order (NLO) on all g(1) deep inelastic scattering data are also presented. They provide two solutions with the gluon spin distribution function Delta G positive or negative, which describe the data equally well. In both cases, at Q(2) = 3 (GeV/c)(2) the first moment of Delta G(x) is found to be of the order of 0.2-0.3 in absolute value. (c) 2007 Elsevier B.V. All rights reserved
The COMPASS experiment at CERN
No full textAbbon P, Albrecht E, Alexakhin VY, et al. The COMPASS experiment at CERN. Nucl.Instrum.Meth. A. 2007;577(3):455-518.The COMPASS experiment makes use of the CERN SPS high-intensity muon and hadron beams for the investigation of the nucleon spin structure and the spectroscopy of hadrons. One or more outgoing particles are detected in coincidence with the incoming muon or hadron. A large polarised target inside a superconducting solenoid is used for the measurements with the muon beam. Outgoing particles are detected by a two-stage, large angle and large momentum range spectrometer. The setup is built using several types of tracking detectors, according to the expected incident rate, required space resolution and the solid angle to be covered. Particle identification is achieved using a RICH counter and both hadron and electromagnetic calorimeters. The setup has been successfully operated from 2002 onwards using a muon beam. Data with a hadron beam were also collected in 2004. This article describes the main features and performances of the spectrometer in 2004; a short summary of the 2006 upgrade is also given. (c) 2007 Elsevier B.V. All rights reserved
