26 research outputs found
A new water anomaly: the temperature dependence of the proton mean kinetic energy
The mean kinetic energy of protons in water is determined by Deep Inelastic
Neutron Scattering experiments, performed above and below the temperature of
maximum density and in the supercooled phase. The temperature dependence of
this energy shows an anomalous behavior, as it occurs for many water
properties. In particular two regions of maximum kinetic energy are identified:
the first one, in the supercooled phase in the range 269 K - 272 K, and a
second one above 273 K. In both these regions the measured proton kinetic
energy exceedes the theoretical prediction based on a semi-classical model.
Noteworthy, the proton mean kinetic energy has a maximum at 277 K, the
temperature of the maximum density of water. In the supercooled metastable
phase the measured mean kinetic energy and the proton momentum distribution
clearly indicate proton delocalization between two H-bonded oxygens.Comment: 4 pages article 2 figure
Neutronics assessment of EU DEMO alternative divertor configurations
Abstract As a demonstration fusion power plant, EU DEMO has to prove the maturity of fusion technology and its viability for electricity production. The central requirements for DEMO rest on its capability to generate significant net electric power to the grid (300 MW to 500 MW) safely and consistently. Plant availability and lifetime will approach that of a commercial fusion power plant. Operating at such regimes presents many complex challenges, of which one is plasma exhaust. To mitigate the risk that the implementation in preceding experimental devices, namely ITER, does not extrapolate to the requirement of DEMO, alternative solutions must be sought. The investigation of alternative divertor configurations was born out of this motive, seeking to resolve a 'critical' challenge for the realisation of DEMO. In this paper, we study the neutronics performance of three concepts: Single Null (SN), Super-X (SX) and X-divertor (XD). This is the first time a preliminary analysis of alternative configurations to the SN baseline has been performed. The shielding proposals and design recommendations presented herein should be integrated with other engineering and physics constraints in future iterations of the chosen divertor concept
Nonlinear optics in a high-index of refraction material
Nonlinear response in a material increases with its index of refraction as
. Commonly, 1 so that diffraction, dispersion, and chromatic
walk-off limit nonlinear scattering. Ferroelectric crystals with a periodic 3D
polarization structure overcome some of these constraints through versatile
Cherenkov and quasi-phase-matching mechanisms. Three-dimensional
self-structuring can also lead to a giant broadband refraction
\cite{DiMei2018}. We here perform second-harmonic-generation experiments in
KTN:Li with . Enhanced response causes wavelength conversion to occur in
the form of bulk Cherenkov radiation without diffraction and chromatic
walk-off, even in the presence of strong wave-vector mismatch and highly
focused beams. The process occurs with an arbitrarily wide spectral acceptance,
more than 100 nm in the near infrared spectrum, an ultra-wide angular
acceptance, up to , with no polarization selectivity, and can
be tuned to allow bulk supercontinuum generation. Results pave the way to
highly efficient versatile and adaptable nonlinear optical devices with the
promise of single-photon-to-single-photon nonlinear optics.Comment: 9 pages, 5 figure
НАБЛЮДЕНИЕ ПОВТОРЯЕМОСТИ ФЕРМИ-ПАСТА-УЛАМА-ЦИНГУ В ОПТИЧЕСКОМ ЭКСПЕРИМЕНТЕ
Recently P.G. Grinevich and P.M. Santini suggested simple approximate formulas for solving periodic Cauchy problem for the focusing Nonlnear Schrodinger Equation (NLS) under assumption that one starts from a small perturbation of the unstable condensate and the number of unstable modes is not too large. With the help of these results, optical experiments in photorefractive crystal where conducted, in which the second and third return of anomalous waves was observed. A good agreement between the experimental data and the predictions made on the basis of the NLS theory was obtained.
P.G. Grinevich was supported by the Russian Science Foundation grant No. 18-11-00316
Preliminary Assessment of Radiolysis for the Cooling Water System in the Rotating Target of {SORGENTINA}-{RF}
The SORGENTINA-RF project aims at developing a 14 MeV fusion neutron source featuring an emission rate in the order of 5-7 x 10(13) s(-1). The plant relies on a metallic water-cooled rotating target and a deuterium (50%) and tritium (50%) ion beam. Beyond the main focus of medical radioisotope production, the source may represent a multi-purpose neutron facility by implementing a series of neutron-based techniques. Among the different engineering and technological issues to be addressed, the production of incondensable gases and corrosion product into the rotating target deserves a dedicated investigation. In this study, a preliminary analysis is carried out, considering the general layout of the target and the present choice of the target material
Observation of Bessel-beam self-trapping
We predict and observe Bessel-beam optical self-trapping in a strongly self-focusing medium. Nonlinearity leads to solutions with a signature pulsing along the propagation direction, a breather that we observe in a photorefractive potassium-lithium-tantalate-niobate crystal. The nonlinear construct is formed as an interference pattern locks together with a diffracting wave