Current Induced Resistive State in Fe(Se,Te) Superconducting Nanostrips

We study the current-voltage characteristics of Fe(Se,Te) thin films deposited on CaF2 substrates in form of nanostrips (width w ~ λ, λ the London penetration length). In view of a possible application of these materials to superconductive electronics and micro-electronics we focus on transport properties in small magnetic field, the one generated by the bias current. From the characteristics taken at different temperatures we derive estimates for the pinning potential U and the pinning potential range δ for the magnetic flux lines (vortices). Since the sample lines are very narrow, the classical creep flow model provides a sufficiently accurate interpretation of the data only when the attractive interaction between magnetic flux lines of opposite sign is taken into account. The observed voltages and the induced depression of the critical current of the nanostrips are compatible with the presence of a low number ([Formula: see text]) magnetic field lines at the equilibrium, a strongly inhomogeneous current density distribution at the two ends of the strips and a reduced Bean Livingston barrier. In particular, we argue that the sharp corners defining the bridge geometry represent points of easy magnetic flux lines injection. The results are relevant for creep flow analysis in superconducting Fe(Se,Te) nanostrips

Alignment of the optical system of the 9.7-m prototype Schwarzchild-Coulder Telescope

International audienceThe novel 9.7m Schwarzschild-Couder Telescope (SCT), utilizing aspheric dual-mirror optical system, has beenconstructed as a prototype medium size γ-ray telescope for the Cherenkov Telescope Array (CTA) observatory.The prototype SCT (pSCT) is designed to achieve simultaneously the wide (≥ 8◦) field of view and the su-perior imaging resolution (0.067◦ per pixel) to significantly improve scientific capabilities of the observatory inconducting the sky surveys, the follow-up observations of multi-messenger transients with poorly known initiallocalization and the morphology studies of γ-ray sources with angular extent. In this submission, we describethe hardware and software implementations of the telescope optical system as well as the methods specificallydeveloped to align its complex optical system, in which both primary and secondary mirrors are segmented.The pSCT has detected Crab Nebula in June 2020 during ongoing commissioning, which was delayed due toworldwide pandemic and is not yet completed. Verification of pSCT performance is continuing and furtherimprovement of optical alignment is anticipate

Monte Carlo studies for the optimisation of the Cherenkov Telescope Array layout

International audienceThe Cherenkov Telescope Array (CTA) is the major next-generation observatory for ground-based very-high-energy gamma-ray astronomy. It will improve the sensitivity of current ground-based instruments by a factor of five to twenty, depending on the energy, greatly improving both their angular and energy resolutions over four decades in energy (from 20 GeV to 300 TeV). This achievement will be possible by using tens of imaging Cherenkov telescopes of three successive sizes. They will be arranged into two arrays, one per hemisphere, located on the La Palma island (Spain) and in Paranal (Chile). We present here the optimised and final telescope arrays for both CTA sites, as well as their foreseen performance, resulting from the analysis of three different large-scale Monte Carlo productions