Explore the vast range of titles available.

With this contribution we show the readout electronics for kinetic inductance detectors (KIDs) that we are developing based on commercial IQ transceivers from National Instruments and using a Virtex 5 class FPGA. It will be the readout electronics of the COSmic Monopole Observer (COSMO) experiment, a ground based cryogenic Martin–Puplett Interferometer searching for the cosmic microwave background spectral distortions. The readout electronics require a sampling rate in the range of tens of kHz, which is both due to a fast rotating mirror modulating the signal and the time constant of the COSMO KIDs. In this contribution we show the capabilities of our readout electronics using Niobium KIDs developed by Paris Observatory for our 5 K cryogenic system. In particular, we demonstrate the capability to detect 23 resonators from frequency sweeps and to readout the state of each resonator with a sampling rate of about 8 kHz. The readout is based on a finite-state machine where the first two states look for the resonances and generate the comb of tones, while the third one performs the acquisition of phase and amplitude of each detector in free running. Our electronics are based on commercial modules, which brings two key advantages: they can be acquired easily and it is relative simple to write and modify the firmware within the LabView environment in order to meet the needs of the experiment.

We publish a data set of environmental and biological data collected in 2000 during the ice-free period in high mountain lakes located above the local timberline in the Alps, in Italy, Switzerland and Austria. Environmental data include coordinates, geographical attributes and detailed information on vegetation, bedrock and land use in lake catchments. Chemical analyses of a sample for each lake collected at the lake surface in Summer 2000 are also reported. Biological data include phytoplankton (floating algae and cyanobacteria), zooplankton (floating animals), macroinvertebrates (aquatic organisms visible to the naked eye living in contact with sediments on lake bottom), benthic diatoms. Diatoms, cladocera and chironomids remains and algal and bacterial pigments were also analysed in lake sediments.

The design and experimental demonstration of a 16-channel frequency-domain multiplexing (FDM) read-out for transition-edge sensor bolometers is presented. This MUX electronics is intended to read out the 326 spiderweb bolometers of the LSPE/SWIPE balloon-borne experiment, which aims at the detection of the B mode polarization of the cosmic microwave background at large angular scales. The cryogenic part of our 16-channel FDM read-out chain features LC resonators composed of custom Nb superconducting inductors and surface mount device ceramic capacitors mounted on boards next to the detector wafers, at 300 mK, while the superconducting quantum interference device board is at 1.6 K. The warm section is based on a modular solution, with mezzanine plug-ins for digital-to-analog converters, analog-to-digital converters and a system-on-chip (based on the Altera Cyclone V field programmable gate array). The warm electronics handles the generation of the FDM tones, the de-multiplexing and the digital signal analysis including, e.g. cosmic ray glitches removal. Here, we recall its specifications, we address noise considerations, and finally we present the latest results obtained using flight models of our custom-designed boards.

We are developing superconducting Microwave Kinetic Inductance Detectors to operate at near infrared and optical wavelengths for astronomy. In order to efficiently meet with the requirements of astronomical applications, we propose to replace the interdigitated capacitor by a metal–insulator–metal capacitor which has the advantage of presenting a larger capacitance value within a much smaller space. The pixel will occupy a space of typically 100 × 85 µm which is nine times less than a typical pixel size using the interdigitated capacitor operating at the same frequency, below 2 GHz.

Twelve Alpine lakes located in the Gran Paradiso National Park, in the western Italian Alps, were sampled during the ice free period in 2008 and analysed for the main morphological, chemical and physical variables in relation to the characteristics of their watershed, with the aim to create a reference database for present and future ecological studies and to support conservation politics with scientific data. The results highlighted that weathering process and direct precipitation input are the main factors determining the hydrochemistry of the studied lakes; moreover the morphological characteristics highly affects the physical properties of the lakes starting from stratification process. The acidification status, the atmospheric input of N compounds and the supply of nutrients were considered in detail. The studied lakes seem to be well preserved by acidification risk. Comparing data from Gran Paradiso National Park with data from European mountain regions ranging in N deposition rates, allows to consider long range anthropogenic impact: the detection of relative low Total Nitrogen (TN) concentration is not necessarily a synonym of a soft impact of long range pollutants, being the final nitrogen concentration dependent from retention process, closely related to catchment characteristics, besides N deposition rates; moreover the dominance of Inorganic Nitrogen (IN) on Organic Nitrogen (ON) highlights that the lakes are interested by N deposition and probably by long range transport of pollutants produced in the urbanized area surrounding the massif. However the Gran Paradiso National Park area is by far less affected by atmospheric pollutants than other Alpine regions, as the Central Alps. Total Phosphorus (TP) concentration in Gran Paradiso lakes (1-13 μg L-1, mean level = 4 μg L-1) is an index of oligotrophic and ultraoligotrophic conditions and according to Redfield's ratio phosphorus is mainly the phytoplankton growth limiting element, assuming a key role in biological processes and food-web dynamics; the high TN:TP ratio values detected in the studied lakes reflects the low N retention capacity of alpine sparse vegetation by comparison with prairies or forests.

The effects of the COVID-19 lockdown on deposition and surface water chemistry were investigated in an area south of the Alps. Long-term data provided by the monitoring networks revealed that the deposition of sulfur and nitrogen compounds in this area has stabilized since around 2010; in 2020, however, both concentrations and deposition were significantly below the average values of the previous decade for SO 4 and NO 3 . Less evident changes were observed for NH 4 and base cation. The estimated decrease of deposition in 2020 with respect to the previous decade was on average − 54% and − 46% for SO 4 and NO 3 , respectively. The lower deposition of SO 4 and NO 3 recorded in 2020 was caused by the sharp decrease of SO 2 and particularly of NO x air concentrations mainly due to the mobility restrictions consequent to the COVID-19 lockdown. The limited effects on NH 4 deposition can be explained by the fact that NH 3 emission was not affected by the lockdown, being mainly related to agricultural activities. A widespread response to the decreased deposition of S and N compounds was observed in a group of pristine freshwater sites, with NO 3 concentrations in 2020 clearly below the long-term average. The rapid chemical recovery observed at freshwater sites in response to the sharp decrease of deposition put in evidence the high resilience potential of freshwater ecosystems in pristine regions and demonstrated the great potential of emission reduction policy in producing further substantial ameliorations of the water quality at sensitive sites.

Polarization sensitivity is a major requirement in future cosmic microwave background studies. Even though lumped-element kinetic inductance detectors (LEKIDs) have already demonstrated a good performance in the millimeter range, the typical configuration based on linear meander inductors exhibits a cross polarization up to 30%. In this work, we propose a new configuration of LEKIDs coupled to a microstrip transmission line where the continuous ground plane has been replaced with parallel lines in order to be used as a polarizing grid. Microwave simulations and preliminary experiments show that the polarizer acts as an effective ground plane with no influence in the electromagnetic performance and that the cross polarization can be decreased to 3%.

Cosmic microwave background (CMB) spectral science is experiencing a renewed interest after the impressive result of COBE–FIRAS in the early Nineties. In 2011, the PIXIE proposal contributed to reopen the prospect of measuring deviations from a perfect 2.725 K planckian spectrum. Both COBE–FIRAS and PIXIE are differential Fourier transform spectrometers (FTSes) capable to operate in the null condition across ∼ 2 frequency decades (in the case of PIXIE, the frequency span is 30 GHz–6 THz). We discuss a complementary strategy to observe CMB spectral distortions at frequencies lower than 250 GHz, down to the Rayleigh–Jeans tail of the spectrum. The throughput advantage that makes the FTS capable of achieving exquisite sensitivity via multimode operation becomes limited at lower frequencies. We demonstrate that an array of 100 cryogenic planar filter-bank spectrometers coupled to single mode antennas, on a purely statistical ground, can perform better than an FTS between tens of GHz and 200 GHz (a relevant frequency window for cosmology) in the hypothesis that (1) both instruments have the same frequency resolution and (2) both instruments are operated at the photon noise limit (with the FTS frequency band extending from ∼ tens of GHz up to 1 THz). We discuss possible limitations of these hypotheses, and the constraints that have to be fulfilled (mainly in terms of efficiency) in order to operate a cryogenic filter-bank spectrometer close to its ultimate sensitivity limit.

We studied hydrochemistry and plankton dynamics in two remote alpine lakes: lake Nivolet superiore (2530 m asl) and lake Trebecchi superiore (2729 m asl) in the Gran Paradiso National Park (Western Italian Alps) in summer 2009. The aim of this study was to enhance the understanding of natural ecological dynamics in the pelagic habitat of alpine lakes by enlarging the number of biotic and abiotic variables usually considered to this end and by increasing the frequency of samplings, generally low in remote lakes. During the eight samplings performed in 2009, chemical and physical variables were measured both in situ and in the laboratory. We also followed the dynamics of all the compartments of the naturally simplified trophic chain of the two lakes from pico-prokaryotes to phytoplankton and zooplankton. Our results confirm the oligotrophic, close-to-pristine state of lake Nivolet and lake Trebecchi as they are not affected by hydromorphological alterations, they are naturally fishless and are not sensitive to acidification risk and acidity pulses. On the other hand, the two lakes have distinct abiotic conditions due to their glacial origin and to the lithological composition of their watersheds. We found some differences in the spatial variation of pico-prokaryotes, phytoplankton and zooplankton due to the different mixing regimes and maximum depth of the two lakes. Conversely, temporal patterns were similar in both lakes, related to ecological interactions and to changes in the abiotic conditions. The rapid succession of events in extreme ecosystems, such as the alpine lakes studied here, confirm the predominant role of external environmental factors (e.g. the duration of the ice-free season) and of ecological interactions among different trophic compartments. This research underlines the importance of seasonal niche partitioning among organisms with different size.

The next generations of cosmic microwave background (CMB) instruments will be dedicated to the detection and characterization of CMB B-modes. To measure this tiny signal, instruments need to control and minimize systematics. Signal modulation is one way to achieve such a control. A new generation of focal planes will include the entire detection chain. In this context, we present a superconducting coplanar switch driven by DC current. It consists of a superconducting microbridge which commutes between its on (superconducting) and off (normal metal) states, depending on the amplitude of the injected current compared to the critical current. If the current injected inside the bridge is lower than the critical current, the phase of the signal passing through the bridge is tunable. A first prototype of this component working as a switch and as a phase shifter at 10 GHz has been made. The principle, the setup, and the first measurements made at 4 K will be shown.