1,720,975 research outputs found
Bismuth-Gold absorber for large area TES spiderweb bolometer
No full textLarge area spiderweb bolometer of about one centimetre diameter are required for matching multimode or quasi-optical cavities in microwave antenna for CMB measurements as proposed for the Large Scale Polarization Explorer balloon borne sky survey at 140, 220, 250 GHz. Possible applications at low frequencies, 40 GHz or less, in single mode are also foreseen. The main drawback of such large absorber is the achievement of an optimal trade-off among the thermal properties, like fast internal thermal diffusivity, heat capacity and milli-second recovery time and EM characteristics, like the matching impedance and EM power dissipation. In parallel with standard micropatterned gold film absorber deposited onto silicon nitride membrane, we have tested the Bismuth Gold in order to reduce the heat capacity even if with an increase of resistivity. Films of Bismuth Gold may have low resistivity under application of a proper post-production thermal cycle. We present the fabrication method of Bismuth Gold films for our microwave absorbers and the bolometer characterization at low temperature
Structural and Morphological Characterization of Iridium and Ir/Au Films for Transition Edge Sensors
No full textSuperconducting Transition Edge Sensors employed in X-ray astrophysics space missions were realized and fully characterized in the Low temperature detector laboratory at UniGe. Several samples of Ir and Ir/Au bilayer films were grown by pulsed laser deposition at different deposition rate, varying thickness and resulting variability in critical temperature (Tc) was observed. In particular, we noticed two classes of films having discrete critical temperature (Tc), one at about the critical temperature of the bulk Ir and one at around 1.6 times compared to the bulk. Structural characterization was made and interesting correlation between critical temperature (Tc) and deposition conditions were found. Detailed X-Ray Diffraction investigations suggest a possible explanation of this effect with a clear correlation between microstrain value, grain size, and critical temperatures of the films. The study has been carried out to optimize the specified conditions to grow the film under which it is possible to accurately predict the critical temperature (Tc) by analyzing the X-ray diffraction patterns of Ir/Au films
Impact of Annealing on TC and Structure of Titanium Thin Films
No full textTransition-edge sensors (TES) are superconducting devices used for detecting particles and electromagnetic radiation, ranging from -ray to mm wavelengths. A fundamental parameter for operations of TES detectors for the desired application is the superconducting critical temperature TC. We are developing TES based bolometers made of metallic Ti films, with an operating temperature of 500mK, to be used for cosmic microwave back-ground (CMB) measurements. We have observed that electron-beam evaporation grown Ti films can reach critical temperatures higher than 500mK when the substrate temperature is kept below some temperature threshold. Discordant critical temperatures of Titanium TES are found in literature and very little information is available about the various TC and relative fabrication process. Critical temperature of Ti films is generally known to be affected by deposition methods, substrates, processing conditions and heating. In the past we tried to tune the critical temperature of titanium thin films by means of post-annealing and we found a regular decrease of TC from 540 mK to 360 mK, in this work we confirm this effect. Further, we have found that titanium film grows with a most stable hcp structure. The annealing process until 260C, does not modify the morphological features of the film. We find also evidences of a shift in XRD peaks that indicate structural changes of the lattice parameters, which could play a role in the TC modification
Focal plane 50 mK anticoincidence detector for the Athena X-ray observatory
No full textPoster presented at the XVIII Internationale Workshop on Neutrino Telescopes (Venice, March 18-22, 2019
The latest performance and refurbishment of the pixelated Timing Counter (pTC) in the MEG II experiment
No full textWe have operated the MEG II pixelated timing counter maintaining its overall timing resolution at high level for precise timing measurement of positrons. Since its construction in 2017, the detector's pixels have shown degradation with high-rate beam irradiation and components (plastic scintillators, SiPMs) aging over time. In 2024, using new 960 SiPMs, we produced and mounted new 80 pixels onto the detector with estimation of the performance improvement
The Phonon-Mediated TES Cosmic Ray Detector for Focal Plane of ATHENA X-Ray Telescope
No full textThe current projects of future X-rays space telescopes foresee high resolving power transition edge sensor (TES) micro-calorimeters arrays as focal plane instrument. In order to full exploit their sensitivity in the space environment, they need an anticoincidence detector to reject the background due to cosmic charged particles. High-energy protons (> 150 MeV) and other charged particle may release in the X-ray calorimeter, the same energy of the X-rays sources under observation. We report the description of the last prototype based on TES calorimeter where a 1-cm2 silicon chip is used as both substrate and absorber. The readout is made of 96 iridium/gold TESs uniformly distributed on its surface and parallel wired. In this paper, we will describe the design, with the preliminary phonon dynamics simulation, the fabrication, of first demonstration model for the ATHENA space telescope project
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
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