Coexistence of Superconductivity and Charge Density Waves in Tantalum Disulfide : Experiment and Theory

The coexistence of charge density wave (CDW) and superconductivity in tantalum disulfide (2H-TaS2) at low temperature is boosted by applying hydrostatic pressures to study both vibrational and magnetic transport properties. Around Pc, we observe a superconducting dome with a maximum superconducting transition temperature Tc=9.1 K. First-principles calculations of the electronic structure predict that, under ambient conditions, the undistorted structure is characterized by a phonon instability at finite momentum close to the experimental CDW wave vector. Upon compression, this instability is found to disappear, indicating the suppression of CDW order. The calculations reveal an electronic topological transition (ETT), which occurs before the suppression of the phonon instability, suggesting that the ETT alone is not directly causing the structural change in the system. The temperature dependence of the first vortex penetration field has been experimentally obtained by two independent methods. While a d wave and single-gap BCS prediction cannot describe the lower critical field Hc1 data, the temperature dependence of the Hc1 can be well described by a single-gap anisotropic s-wave order parameter. © 2020 authors. Published by the American Physical Society

Launch of the Space experiment PAMELA

PAMELA is a satellite borne experiment designed to study with great accuracy cosmic rays of galactic, solar, and trapped nature in a wide energy range protons: 80 MeV-700 GeV, electrons 50 MeV-400 GeV). Main objective is the study of the antimatter component: antiprotons (80 MeV-190 GeV), positrons (50 MeV-270 GeV) and search for antimatter with a precision of the order of 10^-8). The experiment, housed on board the Russian Resurs-DK1 satellite, was launched on June, 15, 2006 in a 350*600 km orbit with an inclination of 70 degrees. The detector is composed of a series of scintillator counters arranged at the extremities of a permanent magnet spectrometer to provide charge, Time-of-Flight and rigidity information. Lepton/hadron identification is performed by a Silicon-Tungsten calorimeter and a Neutron detector placed at the bottom of the device. An Anticounter system is used offline to reject false triggers coming from the satellite. In self-trigger mode the Calorimeter, the neutron detector and a shower tail catcher are capable of an independent measure of the lepton component up to 2 TeV. In this work we describe the experiment, its scientific objectives and the performance in the first months after launch.Comment: Accepted for publication on Advances in Space Researc

Deuteron spectrum measurements under radiation belt with PAMELA instrument

Abstract In this work the results of data analysis of the deuteron albedo radiation obtained in the PAMELA experiment are presented. PAMELA is an international space experiment carried out on board of the satellite Resurs DK-1. The high precision detectors allow to register and identify cosmic ray particles in a wide energy range. The albedo deuteron spectrum in the energy range 70 – 600 MeV/nucleon has been measured

The high energy cosmic ray particle spectra measurements with the PAMELA calorimeter

Abstract Up until now there has been limited, contradictive data on the high energy range of the cosmic ray electron-positron, proton and helium spectra. Due to the limitations of the use of a magnetic spectrometer, over 8 years experimental data was processed using information from a sampling electro-magnetic calorimeter, a neutron detector and scintillator detectors. The use of these devices allowed us to successfully obtain the high energy cosmic ray particle spectra measurements. The results of this study clarify previous findings and greaten our understanding of the origin of cosmic rays

Structural analysis and atomic simulation of Ag/BN nanoparticle hybrids obtained by Ag ion implantation

International audienceThe present paper describes fabrication of Ag/BN nanoparticle hybrids by means of Ag ion implantation into the hollow BN nanoparticles (BNNPs) with a petal-like surface. The structural transformations occurring during Ag ion implantation into BNNPs are studied by low- and high-resolution transmission electron microscopy (TEM), high angle annular dark field scanning TEM (HAADF-STEM) paired with energy-dispersive X-ray (EDX) spectroscopy mapping. The experimental results are theoretically verified in the framework of the classical molecular dynamics (MD) method. Our results have demonstrated that by changing Ag ion energy in the range of 2-20 kV it is possible to selectively fabricate Ag/BNNP nanohybrids with crystalline or amorphous BNNP structures and various Ag NPs distributions over the BNNP thicknesses. © 2016 Elsevier Ltd

Time Fluctuations Of Charged And Neutral Cosmic-ray Component Fluxes As Measured In The Region Of The Brazilian Magnetic Anomaly

Measurements of charged particles, gamma emission and neutrons were fulfilled on balloon in the region of the Brazilian magnetic anomaly on 8 November 1991. The flight lasted approximately 18 hours, including 15 hours on the ceiling at the height of 32 km just during the beginning of the recovery phase of the moderate geomagnetic storm. The main conclusion from the analysis of the obtained experimental data is the following:a) the fluxes of charged and neutral particles were measured and are in agreement with the data of previous works for the close values of geomagnetic cut-off rigidity;b) no sporadic increases of charged- and neutral-particle fluxes were recorded;c) the pulsations of charged particles, gamma-rays and neutrons with characteristic time of ≈ 30 min were found. The sporadic pulsations of charged particles and gamma-rays with shorter periods were observed too. But later pulsations were absent in the neutron flux data. This points to the magnetospheric origin of the observed phenomenon. © 1994 Società Italiana di Fisica.17222323

Cosmic rays studies with the PAMELA space experiment

The instrument PAMELA, in orbit since June 15th, 2006 on board the Russian satellite Resurs DK1, is delivering to ground 16 Gigabytes of data per day. The apparatus is designed to study charged particles in the cosmic radiation, with a particular focus on antiparticles as a possible signature of dark matter annihilation in the galactic halo; the combination of a magnetic spectrometer and different detectors—indeed—allows antiparticles to be reliably identified from a large background of other charged particles. New results on the antiproton-to-proton and positron-to-all-electron ratios over a wide energy range (1–100GeV) have been recently released by the PAMELA Collaboration, and will be summarized in this paper. While the antiproton-to-proton ratio does not show particular differences from an antiparticle standard secondary production, in the positron-to-all-electron ratio an enhancement is clearly seen at energies above 10 GeV. Possible interpretations of this effect will be briefly discussed

Secondary electron and positron fluxes in the near-Earth space observed in the ARINA and PAMELA experiments

Secondary electron and positron fluxes in the energy range from 3 MeV to 7 GeV were measured with the ARINA and PAMELA spectrometers onboard the Resurs-DK satellite launched on June 15, 2006 into an elliptical orbit with an inclination of 70.4° and an altitude of 350-600 km. It is shown that positrons dominate over electrons by a factor of up to 4-5 in the geomagnetic equator region (L < 1.2 and B > 0.25). © Allerton Press, Inc. 2009

The PAMELA space mission

The PAMELA (a Payload for Antimatter-Matter Exploration and Light-nuclei Astrophysics) space mission has been launched on-board the Resurs-DK1 satellite on June 15th 2006 from the Baikonur cosmodrome, in Kazakhstan. PAMELA is a particle spectrometer designed to study charged particles in the cosmic radiation with special focus on the investigation of the nature of dark matter, by mean of the measure of the cosmic-ray antiproton and positron spectra over the largest energy range ever achieved. © 2009