High sensitivity phonon-mediated kinetic inductance detector with combined amplitude and phase read-out

The development of wide-area cryogenic light detectors with good energy resolution is one of the priorities of next generation bolometric experiments searching for rare interactions, as the simultaneous read-out of the light and heat signals enables background suppression through particle identification. Among the proposed technological approaches for the phonon sensor, the naturally-multiplexed Kinetic Inductance Detectors (KIDs) stand out for their excellent intrinsic energy resolution and reproducibility. To satisfy the large surface requirement (several cm$^2$) KIDs are deposited on an insulating substrate that converts the impinging photons into phonons. A fraction of phonons is absorbed by the KID, producing a signal proportional to the energy of the original photons. The potential of this technique was proved by the CALDER project, that reached a baseline resolution of 154$\pm$7 eV RMS by sampling a 2$\times$2 cm$^2$ Silicon substrate with 4 Aluminum KIDs. In this paper we present a prototype of Aluminum KID with improved geometry and quality factor. The design improvement, as well as the combined analysis of amplitude and phase signals, allowed to reach a baseline resolution of 82$\pm$4 eV by sampling the same substrate with a single Aluminum KID

Limits and opportunities of risk analysis application in railway systems

Risk Analysis is a collection of methods widely used in many industrial sectors. In the transport sector it has been particularly used for air transport applications. The reasons for this wide use are well-known: risk analysis allows to approach the safety theme in a stochastic - rather than deterministic - way, it forces to break down the system in sub-components, last but not least it allows a comparison between solutions with different costs, introducing de facto an element of economic feasibility of the project alternatives in the safety field. Apart from the United Kingdom, in Europe the application of this tool in the railway sector is relatively recent. In particular Directive 2004/49/EC (the "railway safety directive") provides for compulsory risk assessment in relation to the activities of railway Infrastructure Managers (IMs) and of Railway Undertakings (RUs). Nevertheless the peculiarity of the railway system - in which human, procedural, environmental and technological components have a continuous interchange and in which human responsibilities and technological functions often overlap - induced the EC to allow wide margins of subjectivity in the interpretation of risk assessment. When enacting Commission Regulation (EC) No 352/2009 which further regulates this subject, a risk assessment is considered positive also if the IM or RU declare to take safety measures widely used in normal practice. The paper shows the results of a structured comparative analysis of the rail sector and other industrial sectors, which illustrate the difficulties, but also the opportunities, of a transfer towards the railway system of the risk analysis methods currently in use for the other systems

Zirconium titanate ceramic pigments: Crystal structure, optical spectroscopy and technological properties

Srilankite-type zirconium titanate, a promising structure for ceramic pigments, was synthesized at 1400 degrees C following three main doping strategies: (a) ZrTi(1-x)A(x)O(4), (b) ZrTi(1-x-y)A(x)B(y)O(4) and (c) Zr1-xCTiO4 where A = Co, Cr, Fe, Mn. Ni or V (chromophores), B = Sb or W (counterions) and C = Pr (chromophore); x = y = 0.05. Powders were characterized by XRD with Rietveld refinements and DRS in the UV-visible-NIR range; technological properties were appraised in several ceramic matrices (frits, glazes and body). Zirconium titanate can be usefully coloured with first row transition elements, giving green and greenish yellow (Co and Ni); orange-buff (Cr and V); tan-brown hues (Mn and Fe). In industrial-like synthesis conditions, a disordered structure as (Zr,Ti)O-2, with both Zr and Ti randomly distributed in the octahedral site, is achieved. Doping with chromophores and counterions induces unit cell dimensions variation and causes an oversaturation in zirconium oxide. Optical spectroscopy reveals the occurrence of Co2+, Cr3+, Fe3+, Mn2+, Mn3+, Ni2+, V3+ and V4+. The zirconium titanate pigments fulfil current technological requirements for low-temperature applications, but exhibit a limited chemico-physical stability for higher firing temperature and in chemically aggressive media

The role of counterions (Mo, Nb, Sb, W) in Cr-, Mn-, Ni- and V-doped rutile ceramic pigments - Part 1. Crystal structure and phase transformations

Rutile is widely used as ceramic pigment for its excellent optical properties, high melting point and intense coloration when doped with transition elements. Industrial ceramic pigments are manufactured from anatase Plus chromophore elements (Cr, Mn, Ni or V) and counterions (Nb, Sb or W). Several solid state reactions occur during the synthesis, involving both the anatase-to-rutile transformation (A --> R) and the formation of accessory phases. The A --> R transition is heavily affected by chromophores with a lowering of the onset temperature: V < Cr < Ni < Mn: the effect of counterions is almost completely hidden by that of chromophores, even if the sequence Mo < Sb < W < Nb may be inferred. The crystal structure of rutile pigments is modified by chromophores and counterions doping; in fact, the doping varies the cell parameters, implies a progressive distortion of the octahedral site and a peculiar variation of the mean Ti-O bond length, with longer basal Ti-O distances and a shorter apical Ti-O distance. The pigment co-doped with V and W is different for its minimum Ti-O bond length distortion (BLD), an almost regular TiO6 octahedron, and the occurrence of Ti3+ within the accessory compound Ti5O9

The Role of counterions (Mo, Nb, Sb, W) in Cr-, Mn-, Ni- and V-doped rutile ceramic pigments. Part 2. Colour and technological properties

Industrial rutile pigments are manufactured using several chromophores: Cr (giving an orange hue), Mn (tan), Ni (yellow) and V (gray); a second element, the so-called counterion (i.e. Mo, Sb, Nb or W) is always added in order to achieve the desired coloration and/or improve the technological properties (e.g. chemico-physical resistance in ceramic bodies and glazes). The colour of these pigments is determined by both metal-ligand charge transfer (Ti4+ <-> O2-) and crystal field effects (transition metals substituting Ti4+ in octahedral coordination). Though the absorbance bands are broad and frequently overlapped, the UV-vis-NIR spectra suggest the occurrence of Cr3+, Mn2+, Mn3+, Ni2+, V3+, and V4+ as chromophores. Rutile pigments are suitable for through-body (up to 1250 degrees C) and glaze applications (up to 1100 degrees C). The best coloration of porcelain stoneware bodies is achieved with Sb or W as counterions, though the higher stability is ensured by Sb, but in the Ti-Ni-W system. The best glaze colours are accomplished by W-bearing pigments, which however are less stable than Nb- or Sb-containing ones, except than for the V + W coupling. This latter represents a new and very interesting Co-free and Cr-free black pigment for low temperature applications

Neutrino current in a gravitational plane wave collision background

The behaviour of a massless Dirac field on a general spacetime background representing two colliding gravitational plane waves is discussed in the Newman-Penrose formalism. The geometrical properties of the neutrino current are analysed and explicit results are given for the special Ferrari-Ibanez solution.Comment: 17 pages, 6 Postscript figures, accepted by International Journal of Modern Physics

Geochemistry and thermodynamic modelling of low-grade metasedimentary rocks from the Sakar-Strandja region, SE Bulgaria

Carbonate-silicate metasedimentary rocks of Triassic protolith age from the Sakar-Strandja region were affected by low-grade metamorphism in the frame of the Maritsa shear zone, which separates two first-order units of the Balkan orogenic system - Rhodopes and Srednogorie zones. The metamorphism was contemporaneous with strike-slip deformation and ductile shearing. We focus attention on whole-rock and mineral chemistry for better understanding of protoliths origin and metamorphic evolution. The major minerals assemblage comprises calcite, dolomite quartz and white mica in variable proportions, minor chlorite, feldspars and rarely biotite. The accessory phases are ilmenite, rutile, monazite and zircon. Most of the samples show well-defined foliation. The siliciclastic component corresponds to shale, wacke or arkose origin and suggests a quartzose sedimentary provenance. The majority of trace elements tend to incorporate in silicate minerals, while Sr shows pronounced preference for calcite. Chondrite normalized REE patterns correspond to continental crust. Immobile elements (La, Th, Sc, Zr, Ti) used for discrimination of tectonic regimes suggest continental island arc setting for the siliciclastic component origin. The P-T pseudosections (Perple_X 6.7.4, Connolly, 1990) combined with observed mineral assemblages and mineral chemistry isopleths of white mica, chlorite and plagioclase correspond to metamorphism in the range 200-400°C and 0.2-0.4 GPa. The results are supported by chlorite solid solution geothermometer. The thermodynamic modelling corroborates petrographic observations and confirms metamorphism at greenschist facies. Geochemical data suggest protoliths origin due to shallow marine terrigenous-carbonate sedimentation with a provenance of typical upper continental crustal composition at continental island arc tectonic setting

Development of Lumped Element Kinetic Inductance Detectors for the W-Band

We are developing a Lumped Element Kinetic Inductance Detector (LEKID) array able to operate in the W-band (75-110 GHz) in order to perform ground-based Cosmic Microwave Background (CMB) and mm-wave astronomical observations. The W-band is close to optimal in terms of contamination of the CMB from Galactic synchrotron, free-free, and thermal interstellar dust. In this band, the atmosphere has very good transparency, allowing interesting ground-based observations with large (>30 m) telescopes, achieving high angular resolution (<0.4 arcmin). In this work we describe the startup measurements devoted to the optimization of a W-band camera/spectrometer prototype for large aperture telescopes like the 64 m SRT (Sardinia Radio Telescope). In the process of selecting the best superconducting film for the LEKID, we characterized a 40 nm thick Aluminum 2-pixel array. We measured the minimum frequency able to break CPs (i.e. $h\nu=2\Delta\left(T_{c}\right)=3.5k_{B}T_{c}$) obtaining $\nu=95.5$ GHz, that corresponds to a critical temperature of 1.31 K. This is not suitable to cover the entire W-band. For an 80 nm layer the minimum frequency decreases to 93.2 GHz, which corresponds to a critical temperature of 1.28 K; this value is still suboptimal for W-band operation. Further increase of the Al film thickness results in bad performance of the detector. We have thus considered a Titanium-Aluminum bi-layer (10 nm thick Ti + 25 nm thick Al, already tested in other laboratories), for which we measured a critical temperature of 820 mK and a cut-on frequency of 65 GHz: so this solution allows operation in the entire W-band.Comment: 16th International Workshop on Low Temperature Detectors, Grenoble 20-24 July 2015, Journal of Low Temperature Physics, Accepte

Active shielding design and optimization of a wireless power transfer (WPT) system for automotive

This study deals with the optimization of a shielding structure composed by multiple active coils for mitigating the magnetic field in an automotive wireless power transfer (WPT) system at 85 kHz. Each active coil is independently powered and the most suitable excitation is obtained by an optimization procedure based on the Gradient Descent algorithm. The proposed procedure is described and applied to shield the magnetic field beside an electric vehicle (EV) equipped with SAE standard coils, during wireless charging. The obtained results show that the magnetic field in the most critical area is significantly reduced (i.e., approximately halved) with a very limited influence on the electrical performances (i.e., WPT efficiency decreases by less than 1 percentage point compared to the case without active shielding)