1,670 research outputs found
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) 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 1547 eV RMS by
sampling a 22 cm 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 824 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
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. ) obtaining
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
Erosive Wear Behavior of High-Chromium Cast Iron: Combined Effect of Erodent Powders and Destabilization Heat Treatments
High-chromium cast irons are frequently used in high-demanding applications, where low production costs and wear performance are key factors. The excellent abrasive resistance of these alloys results from the overall microstructural features, i.e., type, morphology, and distribution of hard primary and secondary carbides, along with the matrix constituents. Such a microstructure is the result of the chemical composition and solidification process, even though it could be further tuned by heat treatments. These latter are usually performed to destabilize the austenite and to induce the precipitation of secondary carbides. The present study investigates the combined effect of destabilization heat treatment route and erodent powder type on the erosive wear behavior of two commercial hypereutectic white cast irons. The as-received and the heat-treated materials were analyzed through optical and scanning electron microscopy, hardness tests, and X-ray diffraction to determine the relationship between microstructural variations and applied heat treatment. The erosive resistance was evaluated per the ASTM G76 standard in a purpose-built air blast test rig. Experiments were performed considering a raw meal powder, commonly used in cement factories, and Al2O3 as erodent powders. The adopted heat treatments were effective in increasing the overall hardness of the material, but this was not directly related to the erosion resistance. By contrast, the relative hardness ratio, i.e., erodent/target hardness, affects the erosion rate and different behaviors in relation to the softer/harder erodent particles were found
Development of Lumped Element Kinetic Inductance Detectors for NIKA
Lumped-element kinetic inductance detectors(LEKIDs) have recently shown
considerable promise as direct absorption mm-wavelength detectors for
astronomical applications. One major research thrust within the N\'eel Iram
Kids Array (NIKA) collaboration has been to investigate the suitability of
these detectors for deployment at the 30-meter IRAM telescope located on Pico
Veleta in Spain. Compared to microwave kinetic inductance detectors (MKID),
using quarter wavelength resonators, the resonant circuit of a LEKID consists
of a discrete inductance and capacitance coupled to a feedline. A high and
constant current density distribution in the inductive part of these resonators
makes them very sensitive. Due to only one metal layer on a silicon substrate,
the fabrication is relatively easy. In order to optimize the LEKIDs for this
application, we have recently probed a wide variety of individual resonator and
array parameters through simulation and physical testing. This included
determining the optimal feed-line coupling, pixel geometry, resonator
distribution within an array (in order to minimize pixel cross-talk), and
resonator frequency spacing. Based on these results, a 144-pixel Aluminum array
was fabricated and tested in a dilution fridge with optical access, yielding an
average optical NEP of ~2E-16 W/Hz^1/2 (best pixels showed NEP = 6E-17 W/Hz^1/2
under 4-8 pW loading per pixel). In October 2010 the second prototype of LEKIDs
has been tested at the IRAM 30 m telescope. A new LEKID geometry for 2
polarizations will be presented. Also first optical measurements of a titanium
nitride array will be discussed.Comment: 5 pages, 12 figures; ISSTT 2011 Worksho
Multi-mode TES bolometer optimization for the LSPE-SWIPE instrument
In this paper we explore the possibility of using transition edge sensor
(TES) detectors in multi-mode configuration in the focal plane of the Short
Wavelength Instrument for the Polarization Explorer (SWIPE) of the
balloon-borne polarimeter Large Scale Polarization Explorer (LSPE) for the
Cosmic Microwave Background (CMB) polarization. This study is motivated by the
fact that maximizing the sensitivity of TES bolometers, under the augmented
background due to the multi-mode design, requires a non trivial choice of
detector parameters. We evaluate the best parameter combination taking into
account scanning strategy, noise constraints, saturation power and operating
temperature of the cryostat during the flight.Comment: in Journal of Low Temperature Physics, 05 January 201
New application of superconductors: high sensitivity cryogenic light detectors
In this paper we describe the current status of the CALDER project, which is
developing ultra-sensitive light detectors based on superconductors for
cryogenic applications. When we apply an AC current to a superconductor, the
Cooper pairs oscillate and acquire kinetic inductance, that can be measured by
inserting the superconductor in a LC circuit with high merit factor.
Interactions in the superconductor can break the Cooper pairs, causing sizable
variations in the kinetic inductance and, thus, in the response of the LC
circuit. The continuous monitoring of the amplitude and frequency modulation
allows to reconstruct the incident energy with excellent sensitivity. This
concept is at the basis of Kinetic Inductance Detectors (KIDs), that are
characterized by natural aptitude to multiplexed read-out (several sensors can
be tuned to different resonant frequencies and coupled to the same line),
resolution of few eV, stable behavior over a wide temperature range, and ease
in fabrication. We present the results obtained by the CALDER collaboration
with 2x2 cm2 substrates sampled by 1 or 4 Aluminum KIDs. We show that the
performances of the first prototypes are already competitive with those of
other commonly used light detectors, and we discuss the strategies for a
further improvement
Characterization of the KID-Based Light Detectors of CALDER
The aim of the Cryogenic wide-Area Light Detectors with Excellent Resolution
(CALDER) project is the development of light detectors with active area of
cm and noise energy resolution smaller than 20 eV RMS,
implementing phonon-mediated kinetic inductance detectors. The detectors are
developed to improve the background suppression in large-mass bolometric
experiments such as CUORE, via the double read-out of the light and the heat
released by particles interacting in the bolometers. In this work, we present
the characterization of the first light detectors developed by CALDER. We
describe the analysis tools to evaluate the resonator parameters (resonant
frequency and quality factors) taking into account simultaneously all the
resonance distortions introduced by the read-out chain (as the feed-line
impedance and its mismatch) and by the power stored in the resonator itself. We
detail the method for the selection of the optimal point for the detector
operation (maximizing the signal-to-noise ratio). Finally, we present the
response of the detector to optical pulses in the energy range of 0-30 keV
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