Development of KI-TWPAs for the DARTWARS Project

Noise at the quantum limit over a broad bandwidth is a fundamental requirement for future cryogenic experiments for neutrino mass measurements, dark matter searches, and Cosmic Microwave Background (CMB) measurements as well as for fast high-fidelity read-out of superconducting qubits. In the last years, Josephson Parametric Amplifiers (JPA) have demonstrated noise levels close to the quantum limit, but due to their narrow bandwidth, only few detectors or qubits per line can be read out in parallel. An alternative and innovative solution is based on superconducting parametric amplification exploiting the travelling-wave concept. Within the Detector Array Readout with Travelling Wave AmplifieRS (DARTWARS) project, we develop Kinetic Inductance Travelling-Wave Parametric Amplifiers (KI-TWPAs) for low temperature detectors and qubit read-out. KI-TWPAs are typically operated in a three-wave mixing (3WM) mode and are characterised by a high gain, a high saturation power, a large amplification bandwidth, and nearly quantum limited noise performance. The goal of the DARTWARS project is to optimise the KI-TWPA design, explore new materials, and investigate alternative fabrication processes in order to enhance the overall performance of the amplifier. In this contribution we present the advancements made by the DARTWARS collaboration to produce a working prototype of a KI-TWPA, from the fabrication to the characterisation

Accreditare le CMM?

Questo articolo vuole ripercorrere gli eventi che portarono ad accreditare in Italia le prove di prestazioni delle CMM secondo la UNI EN ISO 10360-2. L’occasione è quella dello ILC (Inter-Laboratory Comparison) appena organizzato da SA quality for metrology di Stefania Accorsi, di cui lei stessa dà conto nel successivo articolo. Vogliamo qui ripercorrere i risultati di ieri per eventi per comprendere meglio quelli di oggi; ne risulta che, dopo anni e con contesti normativi assai differenti, l’ossatura del lavoro svolto a partire dal 2004, e in particolare lo schema di ILC, è ancora pienamente valido e seguito in quello appena concluso

Optical wood with switchable solar transmittance for all-round thermal management

Technologies enabling passive daytime radiative cooling and daylight harvesting are highly relevant for energy-efficient buildings. Despite recent progress demonstrated with passively cooling polymer coatings, however, it remains challenging to combine also a passive heat gain mechanism into a single substrate for all-round thermal management. Herein, we developed an optical wood (OW) with switchable transmittance of solar irradiation enabled by the hierarchically porous structure, ultralow absorption in solar spectrum and high infrared absorption of cellulose nanofibers. After delignification, the OW shows a high solar reflectance (94.9%) in the visible and high broadband emissivity (0.93) in the infrared region (2.5–25 μm). Owing to the exceptional mass transport of its aligned cellulose nanofibers, OW can quickly switch to a new highly transparent state following phenylethanol impregnation. The solar transmittance of optical wood (OW-II state) can reach 68.4% from 250 to 2500 nm. The switchable OW exhibits efficient radiative cooling to 4.5 °C below ambient temperature in summer (cooling power 81.4 W m−2), and daylight heating to 5.6 °C above the temperature of natural wood in winter (heating power 229.5 W m−2), suggesting its promising role as a low-cost and sustainable solution to all-season thermal management applications

Avogadro and Planck Constants, Two Pillars of the International System of Units

The International System of Units (SI), the current form of the metric system and the world's most used system of units, has been continuously updated and refined since the Metre Convention of 1875 to ensure that it remains up to date with the latest scientific and technological advances. The General Conference on Weights and Measures, at its 26th meeting in 2018, decided to adopt stipulated values of seven physical constants linked to seven measurement units (the second, meter, kilogram, ampere, kelvin, mole, and candela). This paper reviews the technologies developed, in intense and long-standing work, to determine the Avogadro and Planck constants, which are now integral to realising the kilogram

Use of bioresorbable fibers for short-wave infrared spectroscopy using time-domain diffuse optics

We demonstrate the usability of bioresorbable phosphate glass fibers for time-domain diffuse optical spectroscopy (TD-DOS) in the short-wave infrared (SWIR) region of 950-1600 nm, with the use of an InGaAs detector. Bioresorbable fibers for diffuse optics present an exciting prospect due to their ability to be left implanted while retrieving optical properties from deeper regions (few cm) for monitoring treatments. Extending TD-DOS to the SWIR region could be useful to better identify biomarkers such as water, lipids and collagen, given their increase in absorption in this range. We attempt to use the bioresorbable fibers to spectrally identify these biomarkers by measuring a series of biological samples known to contain them, such as porcine muscle, porcine fat and bone. We further validate our measurements by comparing the optical properties of high-scattering solid silicone phantoms retrieved with these bioresorbable fibers with those by a standard Si fiber

Unperturbed Electric Field and Operator Current Towards Ground in HV Substations: a linear relationship between two measurements

As a part of the monitoring of the electric field (E-field) generated in HV substations, a proportionality was observed between the unperturbed E-field and the electric current flowing towards ground from the body of an operator equipped with insulating footwear, measured by an ammeter, in different substation locations. This proportionality cannot be assumed a priori, as the human body capacitive coupling with the HV and surround conductors in the complex substation layout can strongly vary, depending on the measurement point. In the paper, the validity of the proposed indirect approach is validated and quantified, considering an operator moving inside an HV substation. The rationale is discussed by a specific FEM analysis including an anthropomorphic body and confirmed through experimental validation measurement. The linear dependence between the unperturbed E-field and the current flowing from the operator to ground can help speed up and simplify the human exposure assessment to the E-field through indirect, but still sufficiently accurate measurements