High-impedence NbSi TES sensors for studying the cosmic microwave background radiation

Precise measurements of the cosmic microwave background (CMB) are crucial in cosmology, because any proposed model of the universe must account for the features of this radiation. Of all CMB measurements that the scientific community has not yet been able to perform, the CMB B-mode polarization is probably the most challenging from the instrumental point of view. The signature of primordial gravitational waves, which give rise to a B-type polarization, is one of the goals in cosmology today and amongst the first objectives in the field. For this purpose, high-performance low-temperature bolometric cameras, made of thousands of pixels, are currently being developed by many groups, which will improve the sensitivity to B-mode CMB polarization by one or two orders of magnitude compared to the Planck satellite HFI detectors. We present here a new bolometer structure that is able to increase the pixel sensitivities and to simplify the fabrication procedure. This innovative device replaces delicate membrane-based structures and eliminates the mediation of phonons: the incoming energy is directly captured and measured in the electron bath of an appropriate sensor and the thermal decoupling is achieved via the intrinsic electron-phonon decoupling of the sensor at very low temperature. Reported results come from a 204-pixel array of Nb$_{x}$Si$_{1-x}$ transition edge sensors with a meander structure fabricated on a 2-inch silicon wafer using electron-beam co-evaporation and a cleanroom lithography process. To validate the application of this device to CMB measurements, we have performed an optical calibration of our sample in the focal plane of a dilution cryostat test bench. We have demonstrated a light absorption close to 20% and an NEP of about 7$\times10^{-16}$ W/$\sqrt{Hz}$, which is highly encouraging given the scope for improvement in this type of detectors.Comment: 6 pages, 10 figures. arXiv admin note: text overlap with arXiv:1005.0555 by other author

Tunable Superconducting Properties of a-NbSi Thin Films and Application to Detection in Astrophysics

We report on the superconducting properties of amorphous NbxSi1-x thin films. The normal-state resistance and critical temperatures can be separately adjusted to suit the desired application. Notably, the relatively low electron-phonon coupling of these films makes them good candidates for an "all electron bolometer" for Cosmological Microwave Background radiation detection. Moreover, this device can be made to suit both high and low impedance readouts

The commissioning of the CUORE experiment: the mini-tower run

CUORE is a ton-scale experiment approaching the data taking phase in Gran Sasso National Laboratory. Its primary goal is to search for the neutrinoless double-beta decay in 130Te using 988 crystals of tellurim dioxide. The crystals are operated as bolometers at about 10 mK taking advantage of one of the largest dilution cryostat ever built. Concluded in March 2016, the cryostat commissioning consisted in a sequence of cool down runs each one integrating new parts of the apparatus. The last run was performed with the fully configured cryostat and the thermal load at 4 K reached the impressive mass of about 14 tons. During that run the base temperature of 6.3 mK was reached and maintained for more than 70 days. An array of 8 crystals, called mini-tower, was used to check bolometers operation, readout electronics and DAQ. Results will be presented in terms of cooling power, electronic noise, energy resolution and preliminary background measurements

Results from the Cuore Experiment

The Cryogenic Underground Observatory for Rare Events (CUORE) is the first bolometric experiment searching for neutrinoless double beta decay that has been able to reach the 1-ton scale. The detector consists of an array of 988 TeO2 crystals arranged in a cylindrical compact structure of 19 towers, each of them made of 52 crystals. The construction of the experiment was completed in August 2016 and the data taking started in spring 2017 after a period of commissioning and tests. In this work we present the neutrinoless double beta decay results of CUORE from examining a total TeO2 exposure of 86.3kg yr, characterized by an effective energy resolution of 7.7 keV FWHM and a background in the region of interest of 0.014 counts/ (keV kg yr). In this physics run, CUORE placed a lower limit on the decay half- life of neutrinoless double beta decay of 130Te > 1.3.1025 yr (90% C. L.). Moreover, an analysis of the background of the experiment is presented as well as the measurement of the 130Te 2vo3p decay with a resulting half- life of T2 2. [7.9 :- 0.1 (stat.) :- 0.2 (syst.)] x 10(20) yr which is the most precise measurement of the half- life and compatible with previous results

Retrospective evaluation of whole exome and genome mutation calls in 746 cancer samples

Funder: NCI U24CA211006Abstract: The Cancer Genome Atlas (TCGA) and International Cancer Genome Consortium (ICGC) curated consensus somatic mutation calls using whole exome sequencing (WES) and whole genome sequencing (WGS), respectively. Here, as part of the ICGC/TCGA Pan-Cancer Analysis of Whole Genomes (PCAWG) Consortium, which aggregated whole genome sequencing data from 2,658 cancers across 38 tumour types, we compare WES and WGS side-by-side from 746 TCGA samples, finding that ~80% of mutations overlap in covered exonic regions. We estimate that low variant allele fraction (VAF < 15%) and clonal heterogeneity contribute up to 68% of private WGS mutations and 71% of private WES mutations. We observe that ~30% of private WGS mutations trace to mutations identified by a single variant caller in WES consensus efforts. WGS captures both ~50% more variation in exonic regions and un-observed mutations in loci with variable GC-content. Together, our analysis highlights technological divergences between two reproducible somatic variant detection efforts

Identification des évenements de surface dans le détecteurs bolomètriques massifs pour la recherche d évenements rares dans les expériences CUORE et EDELWEISS

Les expériences actuelles de recherche d'évènements rares au moyen de bolomètres massifs comme la détection directe de WIMPs ou les décroissances double béta sans neutrino (0vBB) sont limitées par le bruit de fond radioactif. En particulier, les évènements ayant lieu près des surfaces des détecteurs réduisent sérieusement la sensibilité des expériences telles que EDELWEISS et CUORE. Deux méthodes ont été étudiées pour l'élimination active des évènements de surface. La première, développée initialement pour EDELWEISS, repose sur l'identification de ces évènements en couvrant les surfaces de couches minces thermométriques NbSi sensibles aux phonons hors d'équilibre. Elle a été appliquée aux détecteurs ionisation-chaleur en Ge pour EDELWEISS et à des bolomètres TeO2 (recherche de 0vBB dans 130Te) pour CUORE. La deuxième, développée pour CUORE, repose sur la réalisation de bolomètres composites: des détecteurs auxiliaires fins, collés sur les surfaces agissent comme des écrans actifs qui identifient les particules issues des évènements de surface. Même si le principe physique est différent, dans les deux cas, une étude de forme des impulsions permet une identification efficace des évènements à rejeter. Dans le cas de CUORE, une méthode d'identification des évènements alpha susceptibles de polluer le signal recherché a été développée. L'idée est de réaliser un bolomètre scintillant où la comparaison entre les signaux chaleur et lumière fournit un critère de rejet : une interaction alpha émet moins de lumière qu'une interaction beta ou gamma pour la même énergie. Une tentative pour augmenter la scintillation des cristaux de TeO2 par un dopage adéquat est décrite et analysée.The present limitation for experiments searching for rare events, such as WIMPs interactions and neutrinoless double beta decay (0vBB), is the radioactive background. In particular, near-surface events are the main problem for very sensitive searches based on the bolometric technique, such as EDELWEISS and CUORE. In this work, two techniques have been studied and developed for the active suppression of the surface background. The first approach, pioneered by the EDELWEISS collaboration, concerns the identification of surface events in Ge bolometers (for Dark Matter search) or TeO2 bolometers (for 0vBB search of 130Te) equipped with NbSi thin film thermometers acting as out-of-equilibrium phonons sensor. The second approach, for the moment applied only to TeO2 bolometers in the framework of the CUORE collaboration, consists in the realization of surface-sensitive composite bolometers in which thin auxiliary detectors act as active shields which reveal and identify surface-generated charge particles. In both cases, even if the physical mechanism is different, pulse shape analysis enables an effective rejection procedure. Finally, a further technique has been analysed which has the potential to recognize alpha particles against gamma or beta interactions. The idea is to realize a scintillating bolometer in which the comparison between the heat and the light signal for the same event allows to reject alpha particles, which emit less light than beta/gamma interactions with the same energy. In particular, the attempt to make TeO2 crystals reasonably good scintillators by proper doping is described and analysed.ORSAY-PARIS 11-BU Sciences (914712101) / SudocSudocFranceF

Exposure to Traumatic Events at Work, Post-Traumatic Symptoms, and Professional Quality of Life among Italian Midwives: A Cross-Sectional Study

Background: The aim of this study is to investigate the potential occurrence of post-traumatic stress disorder (PTSD) symptoms, following exposure to traumatic events, in Italian midwives and their consequent influence on the quality of midwives’ professional lives. In addition, data were collected on the major traumatic events described by midwives. Method: A cross-sectional study related the socio-demographic characteristics of 286 midwives with the scores obtained on two assessment scales, one for post-traumatic stress disorder (IES-R) and the other for quality of life (ProQOL V). The percentage of midwives who obtained a score higher than the predetermined threshold value in both questionnaires was noted, and the correlations that emerged were highlighted. Through this qualitative method, their significant work-related traumatic events were investigated to finally detect the prevalence percentage of each category. Results: The proportion of midwives scoring higher than 33 on the IES-R scale, indicating a higher likelihood of PTSD, was 48.6%. Freelancers or outpatient clinic midwives had lower mean IES scores (p = 0.049). A significant inverse correlation was observed between age and IES-R score and between the compassion satisfaction subscale and time since completing education (p = 0.028). A comparison between the IES-R and ProQOL scales showed a statistically significant correlation (p p p < 0.001) subscales. The thematic categorization of traumatic events included mother/child death, mother/child medical complications, relational problems with patients or team members, and organizational problems/medical staff’s inexperience. Conclusions: The emerging data may confirm the data in the literature, namely those showing that midwives are prone to developing work-related PTSD, particularly due to their exposure to traumatic events such as maternal and neonatal death

Prototyping a High Purity Germanium cryogenic veto system for a bolometric detection experiment

International audienceThe use of High Purity Germanium detectors operated in ionization mode at cryogenic temperatures is investigated as an external background mitigation solution for bolometers used in rare-event search experiments. A simple experimental setup with very partial coverage, running a 52-g $\mathrm{Li_2WO_4}$ bolometer sandwiched in-between two 2-cm thick High Purity Germanium cylindrical detectors in a dry cryostat, shows promising rejection to environmental gammas and atmospheric muons backgrounds. The acquired data are used together with a Monte Carlo simulation of the setup to extract the main contributions to the external backgrounds expected in an above ground experiment, such as e.g.~current and future experimental efforts targeting the detection of coherent elastic neutrino-nucleus scattering at reactor facilities. Based on all these results, a $\mathrm{4\pi}$ coverage similar veto system achieving a $\mathcal{O}$(10 keV) energy threshold is expected to achieve a $\mathrm{\gtrsim}$ 70 % and a $\mathrm{\gtrsim}$ 97 % rejection power for gamma-like and muon-like events, respectively