Metahouse: noise-insulating chamber based on periodic structures

Noise pollution remains a challenging problem requiring the development of novel systems for noise insulation. Extensive work in the field of acoustic metamaterials has led to occurrence of various ventilated structures which, however, are usually demonstrated for rather narrow regions of the audible spectrum. In this work, we further extend the idea of metamaterial-based systems developing a concept of a metahouse chamber representing a ventilated structure for broadband noise insulation. Broad stop bands originate from strong coupling between pairs of Helmholtz resonators constituting the structure. We demonstrate numerically and experimentally the averaged transmission -43 dB within the spectral range from 1500 to 16500 Hz. The sparseness of the structure together with the possibility to use optically transparent materials suggest that the chamber may be also characterized by partial optical transparency depending on the mutual position of structural elements. The obtained results are promising for development of novel noise-insulating structures advancing urban science

Ultra-broadband Noise-Insulating Periodic Structures Made of Coupled Helmholtz Resonators

Acoustic metamaterials and phononic crystals represent a promising platform for the development of noise-insulating systems characterized by a low weight and small thickness. Nevertheless, the operational spectral range of these structures is usually quite narrow, limiting their application as substitutions of conventional noise-insulating systems. In this work, the problem is tackled by demonstration of several ways for the improvement of noise-insulating properties of the periodic structures based on coupled Helmholtz resonators. It is shown that tuning of local coupling between the resonators leads to the formation of ultra-broad stop-bands in the transmission spectra. This property is linked to band structures of the equivalent infinitely periodic systems and is discussed in terms of band-gap engineering. The local coupling strength is varied via several means, including introduction of the so-called chirped structures and lossy resonators with porous inserts. The stop-band engineering procedure is supported by genetic algorithm optimization and the numerical calculations are verified by experimental measurements

Polarization by light reflection at metallic surfaces observed in the shape of the Balmer- α line of low density plasmas

The degree of linear polarization of light reflected at metallic surfaces is obtained from the shape of the Balmer-α line measured in a low density plasma. The measurements of the polarization properties of metallic surfaces utilize only the high-resolution emission spectra induced by fast reflected H atoms (≈100 eV) in ArH plasmas. The measurements are performed at two different lines-of-sight to the target surfaces of Mo and Cu. Only at the observation angle close to the Brewster one, a significant drop of the measured red-shifted signal is detected for the Mo target: the red-shifted emission reduces by ≈50% depending on whether the transverse (S) or the parallel (P) polarization component of the reflected light is selected. In contrast to this, a very weak change of emission is observed for the Cu surface for the same angle. The spectra measured in front of the Mo target were modeled utilizing the energy and angular distribution of reflected atoms and excitation of the cross section of Ar-H collision combined in a Doppler-shifted emission model. A good agreement with the theoretical calculations is found for polarization components (except for the weak P polarization at 70°). Finally, the undercosine distribution of the reflected atoms with b ≈ 0.2 (b is the power of the cosine distribution) shows the best agreement with the spectra measured at both lines-of-sigh

Mirror Station for studies of the protection of diagnostic mirrors from impurity contamination in ITER: Design and first results

Optical and laser-based diagnostics in ITER will use mirrors to transmit plasma radiation and laser light to the corresponding detectors and cameras. Mirrors will be sputtered by the fast plasma particles and contaminated by impurities leading to the degradation of the reflectivity and hampering the performance of corresponding diagnostics. Dedicated measures were proposed to minimize the impurity deposition comprising the use of shutters and fins inside diagnostic ducts to trap impurities on their way toward the mirror located in the end of these ducts. Modeling results predict at least 7-fold suppression of the deposition for the duct having four fins located at the distance of a half of a diameter from each other. The Mirror Station (MS) was designed to validate modeling predictions and to study the suppression of deposition inside of diagnostic ducts. The MS contained cylindrical and cone-shaped tubes of different lengths with smooth and shaped geometry of ducts. The MS was exposed in the midplane port of TEXTOR for about 3960 s of plasma operation. After exposure, no drastic suppression of deposition was observed in the cylindrical ducts with fins. In the conical tubes no deposition was detected outlining the advantages of a cone form

Entwicklung und Test von Prototypkomponenten für ITER

Das Bundesministerium für Bildung und und Forschung (BMBF) stellte in 2007/2008 Mittel imRahmen der Projektförderung zur Verfügung, mit der Zielsetzung eine stärker sichtbareBeteiligung der deutschen Fusionsinstitute am Aufbau von ITER zu erreichen, sowie dieChancen deutscher Unternehmen auf die Übernahme von Aufträgen für den Aufbau vonITER zu stärken.Eine wichtige Zielsetzung des hier beschriebenen Forschungsvorhabens (Projektnummer03FUS0007) war es demnach, kritische Prototyp-Komponenten für ITER zu entwickeln undzu testen, sowie entsprechende Mess- und Prüfeinrichtungen aufzubauen. Gleichzeitigwurde in der Projektbearbeitung sehr eng mit einer ganzen Reihe von Unternehmenzusammengearbeitet, um so einen intensiven Know-How Transfer in beiden Richtungen imHinblick auf die Entwicklung von Komponenten für Fusionsanlagen zu erreiche

Design status of the ITER core CXRS diagnostic setup

The Charge eXchange Recombination Spectroscopy diagnostic system on the ITER plasma core (CXRS core) will provide spatially resolved measurements of plasma parameters. The optical front-end is located in upper port 3 and the light of 460–665 nm is routed to spectrometers housed in the tritium building. This paper describes the layout of the optical system in the port plug, cell and interspace areas. The layout is a continuation of the developments described in [1] and takes into account changes in the design of the upper port plug, considerations for the system lifetime as well as internal and external tolerances on the optical chain. The layout was selected also with a number of additional criteria, including optical performance, radiation shielding, maintainability and robustness. A free-space optical chain was added pushing the optical fibres to the port cell. A line-of-sight finder imaging apertures and masks in the optical chain was added to enable determination of deviations within the optical chain and stabilise the image on the fibres. Where feasible, existing solutions for sub-systems such as the shutter were adapted to the layout