Structural properties of erbium-activated silica-titania glasses: modeling by molecular dynamics method

Here, we use molecular dynamics simulation to reconstruct a silica-titania glass with a Ti/Si atomic ratio of 8.5% activated by 0.7 at% of erbium. These quantities are chosen because they give both refractive index and optically ions concentration suitable for applications. We use a modified Born-Mayer-Huggins potential taking into account a three- body interaction. The distribution of TiO4 and SiO4 units as well as the bridging to non-bridging oxygen ratios are evaluated. The local environment of rare-earth ions is also analyzed. In particular, the clustering of erbium is discussed. From the simulated structure, the crystal-field strength is computed and discussed according to the Er3+ local environment. Finally, results are compared with information obtained by Raman and photoluminescence spectra

Development of a new generation of 3D pixel sensors for HL-LHC

This paper covers the main technological and design aspects relevant to the development of a new generation of thin 3D pixel sensors with small pixel size aimed at the High-Luminosity LHC upgrades. (C) 2015 Elsevier B.V. All rights reserved

FEM-based linear inverse modeling using a 3D source array to image magma chambers with free geometry. Application to InSAR data from Rabaul Caldera (PNG).

This article is subject to a CC Attribution 3.0 License.In this study, we present a method to fully integrate a family of finite element models (FEMs) into the regularized linear inversion of InSAR data collected at Rabaul caldera (PNG) between February 2007 and December 2010. During this period the caldera experienced a long-term steady subsidence that characterized surface movement both inside the caldera and outside, on its western side. The inversion is based on an array of FEM sources in the sense that the Green’s function matrix is a library of forward numerical displacement solutions generated by the sources of an array common to all FEMs. Each entry of the library is the LOS surface displacement generated by injecting a unity mass of fluid, of known density and bulk modulus, into a different source cavity of the array for each FEM. By using FEMs, we are taking advantage of their capability of including topography and heterogeneous distribution of elastic material properties. All FEMs of the family share the same mesh in which only one source is activated at the time by removing the corresponding elements and applying the unity fluid flux. The domain therefore only needs to be discretized once. This precludes remeshing for each activated source, thus reducing computational requirements, often a downside of FEM-based inversions. Without imposing an a-priori source, the method allows us to identify, from a least-squares standpoint, a complex distribution of fluid flux (or change in pressure) with a 3D free geometry within the source array, as dictated by the data. The results of applying the proposed inversion to Rabaul InSAR data show a shallow magmatic system under the caldera made of two interconnected lobes located at the two opposite sides of the caldera. These lobes could be consistent with feeding reservoirs of the ongoing Tavuvur volcano eruption of andesitic products, on the eastern side, and of the past Vulcan volcano eruptions of more evolved materials, on the western side. The interconnection and spatial distribution of sources find correspondence in the petrography of the volcanic products described in literature and in the dynamics of the single and twin eruptions that characterize the caldera. As many other volcanoes, Rabaul caldera is an active and dangerous volcanic system whose dynamics still need to be understood to effectively predict the behavior of future eruptions. The good results obtained from the application of the method to Rabaul caldera show that the proposed linear inversion based on the FEM array of sources is suitable to generate models of magmatic systems. The method can image in space and time the complex free geometry of the source that generates the deformation, widening our understanding of deformational sources and their dynamics. This takes source modeling a step towards more realistic source models.Peer Reviewe

32-Channel silicon strip detection module for combined X-ray fluorescence spectroscopy and X-ray diffractometry analysis

A compact detection module for the simultaneous measurement of XRF and XRD in portable analytical applications, in particular in the mining sector, is presented. The detector head is based on 32 silicon strip detectors, fabricated with a low-leakage technology by FBK and readout by two 16-channel low-noise CUBE charge-sensitive amplifiers. The design of the module and its characterization are reported. Multiple configurations are experimentally compared in terms of strip length, spacing, collimation and charge sharing effects. The optimal configuration for a strip length of 6 mm and pitch 0.2 mm is thus identified. It offers an energy resolution of better than 200 eV at 5.9 keV with moderate cooling (−10°C) and peaking time of 14 μs

The INFN-FBK "Phase-2" R&D program

We report on the 3-year INFN ATLAS-CMS joint research activity in collaboration with FBK, started in 2014, and aimed at the development of new thin pixel detectors for the High Luminosity LHC Phase-2 upgrades. The program is concerned with both 3D and planar active-edge pixel sensors to be made on 6" p-type wafers. The technology and the design will be optimized and qualified for extreme radiation hardness (2×1016 neq cm-2). Pixel layouts compatible with present (for testing) and future (RD53 65nm) front-end chips of ATLAS and CMS are considered. The paper covers the main aspects of the research program, from the sensor design and fabrication technology, to the results of initial tests performed on the first prototypes. © 2015 Elsevier B.V

倏逝场作用氧化石墨烯大能量耗散孤子锁模双包层光纤激光器

报道了倏逝场作用氧化石墨烯的可饱和吸收体用于锁模掺镱双包层光纤激光器,产生大能量151.54nJ耗散孤子.利用熔锥光纤倏逝场诱导沉积氧化石墨烯方法,所制备的可饱和吸收体不仅拥有耐高功率、光纤兼容等优点;而且,熔锥光纤引入光带通滤波,有益于耗散孤子在光纤激光腔中形成.同时结合光纤包层泵浦技术,高脉冲能量耗散孤子在锁模掺镱双包层光纤激光器中被获得,产生的耗散孤子单脉冲能量高达151.54nJ,重复频率271.4kHz,信噪比57dB.国家自然科学基金(61275050);高等学校博士学科点专项科研基金(20120121110034

Preliminary results of 3D-DDTC pixel detectors for the ATLAS upgrade

3D Silicon sensors fabricated at FBK-irst with the Double-side Double Type Column (DDTC) approach and columnar electrodes only partially etched through p-type substrates were tested in laboratory and in a 1.35 Tesla magnetic field with a 180GeV pion beam at CERN SPS. The substrate thickness of the sensors is about 200um, and different column depths are available, with overlaps between junction columns (etched from the front side) and ohmic columns (etched from the back side) in the range from 110um to 150um. The devices under test were bump bonded to the ATLAS Pixel readout chip (FEI3) at SELEX SI (Rome, Italy). We report leakage current and noise measurements, results of functional tests with Am241 gamma-ray sources, charge collection tests with Sr90 beta-source and an overview of preliminary results from the CERN beam test.Comment: 8 pages, 8 figures, presented at RD09 - 9th International Conference on Large Scale Applications and Radiation Hardness of Semiconductor Detectors, 30 September - 2 October 2009, Florence, Ital

Preliminary results of 3D-DDTC pixel detectors for the ATLAS upgrade

Presented at: 9th International Conference on Large Scale Applications and Radiation Hardness of Semiconductor Detectors - RD09. Florence, Italy, 30 September - 2 October 20093D Silicon sensors fabricated at FBK-irst with the Double-side Double Type Column (DDTC) approach and columnar electrodes only partially etched through p-type substrates were tested in laboratory and in a 1.35 Tesla magnetic field with a 180GeV pion beam at CERN SPS. The substrate thickness of the sensors is about 200μm, and different column depths are available, with overlaps between junction columns (etched from the front side) and ohmic columns (etched from the back side) in the range from 110μm to 150μm. The devices under test were bump bonded to the ATLAS Pixel readout chip (FEI3) at SELEX SI (Rome, Italy). We report leakage current and noise measurements, results of functional tests with Am241 γ-ray sources, charge collection tests with Sr90 β-source and an overview of preliminary results from the CERN beam test.publishedVersio