930 research outputs found
Optical Coatings as Mirrors for Optical Diagnostics
The aim of this work was to provide a comprehensive insight concerning coated films which might be used for first mirrors in ITER. The influence of the mirror crystallite size has been addressed as well as the coating techniques to provide nanocrystalline films. Tests of coated mirrors both in laboratories and in tokamaks are reviewed. For the tokamak tests a wide angle camera system has been installed in JET-ILW which is composed of a mirror box with 3 stainless steel mirrors coated with rhodium viewing the torus through a conically shaped aperture. The system delivered the required image quality for plasma monitoring and wall protection. No or insignificant degradation of the optical transmittance has been observed during the experimental campaign in 2014 with about 3000 plasma pulses in different magnetic field configurations
Coastal flooding risk calculations for the Belgian coast
Coastal flooding risk calculations are carried out for the entire Belgian coastal zone to support the management ofthe coastal defence system. The floodprone low-lying coastal area has an average width of 20 km and is locatedon average 2 m below the surge level of an annual storm. The natural sea defences are sandy beaches anddunes, which have been strengthened by revetments in the coastal towns. The Belgian standard of coastalprotection is to be safe against a surge level with a return period of 1000 years, but at present it is investigated if and how this standard could be redefined based on risk analysis
Limiter lock systems at TEXTOR: flexible tools for plasma-wall investigation
Limiter lock systems on the top and the bottom of the TEXTOR vessel are essential elements for experimental investigations of plasma-wall interaction in a tokamak. The lock systems are designed as user facilities that allow the insertion of wall elements (limiter) and tools for diagnostic (electrical probes, gas injection) without breaking the TEXTOR vacuum. The specially designed holder on top of the central carrier and a powerful vacuum pump system permit the exchange of components within similar to1 h. Up to ten electrical signals, four thermocouples, and a gas supply can be connected at the holder interface. Between discharges, the inserted component can be positioned radially and turned with respect to the toroidal magnetic field. Additionally, the central carrier is electrically isolated to apply bias voltages and currents up to 1 kV and 1 kA, respectively.An important feature of the lock system is the good access for optical spectroscopic observation of the inserted components in the vicinity of the edge plasma. The whole spectrum from ultraviolet to infrared is covered by spectrometers and filters combined with cameras. Toroidally and poloidally resolved measurements are obtained front the view on top of the probes while the tangential poloidal view delivers radially and toroidally resolved information.A programmable logic controller (Simatic S5) that is operated inside the TEXTOR bunker and from remote locations outside the concrete wall drives all possible features of the lock system
Two-particle interference of electron pairs on a molecular level
We investigate the photo-doubleionization of molecules with 400 eV
photons. We find that the emitted electrons do not show any sign of two-center
interference fringes in their angular emission distributions if considered
separately. In contrast, the quasi-particle consisting of both electrons (i.e.
the "dielectron") does. The work highlights the fact that non-local effects are
embedded everywhere in nature where many-particle processes are involved
O(a)-improved quark action on anisotropic lattices and perturbative renormalization of heavy-light currents
We investigate the Symanzik improvement of the Wilson quark action on
anisotropic lattices. Taking first a general action with nearest-neighbor and
clover interactions, we study the mass dependence of the ratio of the hopping
parameters, the clover coefficients, and an improvement coefficient for
heavy-light vector and axial vector currents. We show how tree-level
improvement can be achieved. For a particular choice of the spatial Wilson
coupling, the results simplify, and improvement is possible.
(Here is the bare quark mass and the temporal lattice spacing.)
With this choice we calculate the renormalization factors of heavy-light
bilinear operators at one-loop order of perturbation theory employing the
standard plaquette gauge action.Comment: 26 pages, 8 figure
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Results of the MAJORANA DEMONSTRATOR's Search for Double-Beta Decay of 76Ge to Excited States of 76Se
The MAJORANA DEMONSTRATOR is searching for double-beta decay of 76Ge to excited states (E.S.) in 76Se using a modular array of high purity Germanium detectors. 76Ge can decay into three E.S.s of 76Se. The E.S. decays have a clear event signature consisting of a ββ-decay with the prompt emission of one or two γ-rays, resulting in with high probability in a multi-site event. The granularity of the DEMONSTRATOR detector array enables powerful discrimination of this event signature from backgrounds. Using 21.3 kg-y of isotopic exposure, the DEMONSTRATOR has set world leading limits for each E.S. decay, with 90% CL lower half-life limits in the range of (0.56 2.1) ⋅ 1024 y. In particular, for the 2v transition to the first 0+ E.S. of 76Se, a lower half-life limit of 0.68 ⋅ 1024 at 90% CL was achieved
Photoproduction of meson pairs: First measurement of the polarization observable I^s
The polarization observable I^s, a feature exclusive to the acoplanar
kinematics of multi-meson final states produced via linearly polarized photons,
has been measured for the first time. Results for the reaction g p -> p pi0 eta
are presented for incoming photon energies between 970 MeV and 1650 MeV along
with the beam asymmetry I^c. The comparably large asymmetries demonstrate a
high sensitivity of I^s to the dynamics of the reaction. Fits using
Bonn-Gatchina partial wave analysis demonstrate that the new polarization
observables carry significant information on the contributing partial waves.Comment: 11 pages, 6 figures, v2 to appear in Phys. Lett.
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