Analysis of test beam data taken with a prototype of TPC with resistive Micromegas for the T2K Near Detector upgrade

In this paper we describe the performance of a prototype of the High Angle Time Projection Chambers (HA-TPCs) that are being produced for the Near Detector (ND280) upgrade of the T2K experiment. The two HA-TPCs of ND280 will be instrumented with eight Encapsulated Resistive Anode Micromegas (ERAM) on each endplate, thus constituting in total 32 ERAMs. This innovative technique allows the detection of the charge emitted by ionization electrons over several pads, improving the determination of the track position. The TPC prototype has been equipped with the first ERAM module produced for T2K and with the HA-TPC readout electronics chain and it has been exposed to the DESY Test Beam in order to measure spatial and dE/dx resolution. In this paper we characterize the performances of the ERAM and, for the first time, we compare them with a newly developed simulation of the detector response. Spatial resolution better than 800 ${\mu \rm m}$ and dE/dx resolution better than 10% are observed for all the incident angles and for all the drift distances of interest. All the main features of the data are correctly reproduced by the simulation and these performances fully fulfill the requirements for the HA-TPCs of T2K

Characterization of Charge Spreading and Gain of Encapsulated Resistive Micromegas Detectors for the Upgrade of the T2K Near Detector Time Projection Chambers

An upgrade of the near detector of the T2K long baseline neutrino oscillation experiment is currently being conducted. This upgrade will include two new Time Projection Chambers, each equipped with 16 charge readout resistive Micromegas modules. A procedure to validate the performance of the detectors at different stages of production has been developed and implemented to ensure a proper and reliable operation of the detectors once installed. A dedicated X-ray test bench is used to characterize the detectors by scanning each pad individually and to precisely measure the uniformity of the gain and the deposited energy resolution over the pad plane. An energy resolution of about 10% is obtained. A detailed physical model has been developed to describe the charge dispersion phenomena in the resistive Micromegas anode. The detailed physical description includes initial ionization, electron drift, diffusion effects and the readout electronics effects. The model provides an excellent characterization of the charge spreading of the experimental measurements and allowed the simultaneous extraction of gain and RC information of the modules

Southern African Large Telescope Spectroscopy of BL Lacs for the CTA project

In the last two decades, very-high-energy gamma-ray astronomy has reached maturity: over 200 sources have been detected, both Galactic and extragalactic, by ground-based experiments. At present, Active Galactic Nuclei (AGN) make up about 40% of the more than 200 sources detected at very high energies with ground-based telescopes, the majority of which are blazars, i.e. their jets are closely aligned with the line of sight to Earth and three quarters of which are classified as high-frequency peaked BL Lac objects. One challenge to studies of the cosmological evolution of BL Lacs is the difficulty of obtaining redshifts from their nearly featureless, continuum-dominated spectra. It is expected that a significant fraction of the AGN to be detected with the future Cherenkov Telescope Array (CTA) observatory will have no spectroscopic redshifts, compromising the reliability of BL Lac population studies, particularly of their cosmic evolution. We started an effort in 2019 to measure the redshifts of a large fraction of the AGN that are likely to be detected with CTA, using the Southern African Large Telescope (SALT). In this contribution, we present two results from an on-going SALT program focused on the determination of BL Lac object redshifts that will be relevant for the CTA observatory

Raman study of the spinel-to-layered phase transformation in sol–gel LiCoO2 cathode powders as a function of the post-annealing temperature

International audienc

Development of a thin flexible Li battery design with a new gel polymer electrolyte operating at room temperature

In this study, we develop a new Li-metal battery design merging with IoT requirements, mainly the low thickness, the thermal stability and the flexibility. To reach these specifications, we firstly prepared an efficient gel polymer electrolyte (GPE) composed of a PVDF-HFP polymer network, a LiFSI: Pyr13FSI liquid binary solution and a lithium montmorillonite Li-MMT clay. The as-synthesized material exhibits a high ionic conductivity (0.48 mS cm-1 at 25 ◦C) and a good thermal stability, up to 140 ◦C. In parallel, a new battery design with an optimized ratio of packaging to active material thickness is developed. In this design, copper foils act both as current collector and as battery casing, decreasing the overall cell thickness. Li metal batteries are realized using the developed GPE material and this new battery design. The cell thickness is 360 and 760 μm for single side and double-sided architectures respectively. These batteries show well functioning under high bending and exhibit a good cycling ability with a remaining capacity higher than 85% after more than 200 cycles at 25 ◦C. Thanks to the combination of the original Cu packaging and the flexible GPE membrane, developed Li-metal batteries exhibit promising properties to merge with the new IoT requirements.EnSO projec

Impact of a theory-informed and user-centered stroke information campaign on the public's behaviors, attitudes, and knowledge when facing acute stroke: a controlled before-and-after study

International audienceBACKGROUND: Public awareness of stroke symptoms is a key factor to ensure access to reperfusion strategies in due time. We designed and launched a regional theory-informed and user-centered information campaign and assessed its impact on emergency medical services (EMS) calls for stroke suspicion, time-to-call, and public attitudes and awareness concerning stroke. METHODS: A controlled before-and-after study was conducted during 3 sequential time-periods in 2 separate counties. Key messages of the campaign were underpinned by stroke representations and the theory of planned behavior, and focused on recognition of stroke warning signs and the need to call EMS urgently. The campaign included posters, leaflets, adverts and films displayed in bus and subway stations, internet, social networks, and local radio. Outcome measures on behavior, attitudes, and knowledge were assessed before the launch of the campaign, at 3 months, and 12 months. RESULTS: The number of EMS calls for stroke suspicion increased by 21% at 12 months in the intervention county and this change was significantly different to that observed in the control county (p = 0.02). No significant changes were observed regarding self-reported attitudes in case of stroke. An 8% significant increase in recognizing at least 2 stroke warning signs was observed in the intervention county (p = 0.04) at 3 months, while it did not change significantly in the control county (p = 0.6). However, there was no significant difference in warning sign recognition between both counties (p = 0.16). CONCLUSION: The campaign significantly improved public's behavior of calling EMS, although stroke knowledge was not improved as much as expected. Repeating these campaigns over time might further help improve timeliness and access to reperfusion strategies. TRIAL REGISTRATION: Clinical Trial Registration-URL: http://www.clinicaltrials.gov . Unique identifier: NCT02846363