Anisotropic resistance change of La0.7Sr0.3MnO3 thin films effected by in-plane axial strain

Thin films of La0.7Sr0.3MnO3 grown on (001) NdGaO3 substrate using vertical hot wall Injection CVD reactor were investigated by means of standard fish-bellied beam inducing uniaxial compressive (or tensile) strain of the films. The measurements were carried out in current direction both parallel (longitudinal resistance R1) and perpendicular (transversal resistance R1) to the strain direction. The compression along [100], [110], [010] and [110] directions on films having 8 nm thickness showed the strong anisotropy of strain induced resistance change. The compression along [010] and [l10] directions caused the decrease of the film resistance while the compression along [100] and [110] directions increased this resistance. The maximum obtained relative resistance change was about 27% at strain 0.005. This effect appeared in both longitudinal and transversal directions of the electric current. The experimental results are discussed in terms of external strain influence on anisotropically strained La0.7Sr0.3 MnO3 film lattice produced as a result of large mismatch between substrate and film lattice constants

Distributed laboratory system for characterization of current distribution in electromagnetic rail launchers

This paper presents the activity of a Distributed Measurement Laboratory on a challenging topic: the characterization of current distribution in electromagnetic rail launchers. Such experiments are characterized by strong transient magnetic fields, very fast moving conductors and the use of pulsed power in the GW range. Due to the high complexity of the investigated phenomenon an international network of laboratories is seen as an appropriate approach. The development of a proper network technology and a common platform is an important aspect to make the distributed measurement system efficient. Currently, various European laboratories have formed the European Pulsed Power Laboratories (EPPL) in order to improve their individual capacities and to develop networking measurement systems in the field of pulsed power R&D

Distributed Laboratory System for Characterization of Current Distribution in Electromagnetic Rail Launchers

This paper presents the activity of a Distributed Measurement Laboratory on a challenging topic: the character­ization of current distribution in electromagnetic rail launchers. Such experiments are characterized by strong transient magnetic fields, very fast moving conductors and the use of pulsed power in the GW range. Due to the high complexity of the investigated phenomenon an international network of laboratories is seen as an appropriate approach. The development of a proper network technology and a common platform is an important aspect to make the distributed measurement system efficient. Currently, various European laboratories have formed the European Pulsed Power Laboratories (EPPL) in order to improve their individual capacities and to develop networking measurement systems in the field of pulsed power R&D

Symmetric and asymmetric shocked gas jets for laser-plasma experiments

International audienceShocks in supersonic flows offer both high density and sharp density gradients that are used, for instance, for gradient injection in laser-plasma accelerators. We report on a parametric study of oblique shocks created by inserting a straight axisymmetric section at the end of a supersonic “de Laval” nozzle. The effect of different parameters, such as the throat diameter and straight section length on the shock position and density, is studied through computational fluid dynamics (CFD) simulations. Experimental characterizations of a shocked nozzle are compared to CFD simulations and found to be in good agreement. We then introduce a newly designed asymmetric shocked gas jet, where the straight section is only present on one lateral side of the nozzle, thus providing a gas profile well adapted for density transition injection. In this case, full-3D fluid simulations and experimental measurements are compared and show excellent agreement

Demonstration of stable long-term operation of a kilohertz laser-plasma accelerator

International audienceWe report on the stable and continuous operation of a kilohertz laser-plasma accelerator. Electron bunches with 2.6 pC charge and 2.5 MeV peak energy were generated via injection and trapping in a downward plasma density ramp. This density transition was produced in a specially designed asymmetrically shocked gas jet. The reproducibility of the electron source was also assessed over a period of a week and found to be satisfactory with similar values of the beam charge and energy. Particle in cell simulations confirm the role of the shock and the density transition in the electron injection mechanism. These results show that the reproducibility and stability of the laser-plasma accelerator are greatly enhanced on the long-term scale when using a robust scheme for density gradient injection

Optimization and stabilization of a kilohertz laser-plasma accelerator

Laser–plasma acceleration at kilohertz repetition rates has recently been shown to work in two different regimes with pulse lengths of either 30 fs or 3.5 fs. We now report on a systematic study in which a large range of pulse durations and plasma densities were investigated through continuous tuning of the laser spectral bandwidth. Indeed, two laser–plasma accelerator (LPA) processes can be distinguished, where beams of the highest quality, with a charge of 5.4 pC and a spectrum peaked at 2–2.5 MeV, are obtained with short pulses propagating at moderate plasma densities. Through particle-in-cell (PIC) simulations, the two different acceleration processes are thoroughly explained. Finally, we proceed to show the results of a 5-h continuous and stable run of our LPA accelerator accumulating more than 18 ???? 106 consecutive shots, with a charge of 2.6 pC and a peaked 2.5 MeV spectrum. A parametric study of the influence of the laser driver energy through PIC simula- tions underlines that this unprecedented stability was obtained thanks to micro-scale density gradient injection. Together, these results repre- sent an important step toward stable laser–plasma accelerated electron beams at kilohertz repetition rates

Optimization and stabilization of a kilohertz laser-plasma accelerator

Article No. 033105Laser-plasma acceleration at kilohertz repetition rates has recently been shown to work in two different regimes with pulse lengths of either 30 fs or 3.5 fs. We now report on a systematic study in which a large range of pulse durations and plasma densities were investigated through continuous tuning of the laser spectral bandwidth. Indeed, two laser-plasma accelerator (LPA) processes can be distinguished, where beams of the highest quality, with a charge of 5.4 pC and a spectrum peaked at 2-2.5MeV, are obtained with short pulses propagating at moderate plasma densities. Through particle-in-cell (PIC) simulations, the two different acceleration processes are thoroughly explained. Finally, we proceed to show the results of a 5-h continuous and stable run of our LPA accelerator accumulating more than 18 x 10 6 consecutive shots, with a charge of 2.6 pC and a peaked 2.5MeV spectrum. A parametric study of the influence of the laser driver energy through PIC simulations underlines that this unprecedented stability was obtained thanks to micro-scale density gradient injection. Together, these results represent an important step toward stable laser-plasma accelerated electron beams at kilohertz repetition ratesFizikos katedraFizinių ir technologijos mokslų centrasFizinių ir technologijos mokslų centras, VilniusVytauto Didžiojo universiteta

Genetics of Plasma Bilirubin and Associations between Bilirubin and Cardiometabolic Risk Profiles in Danish Children and Adolescents

Bilirubin is the end product of heme catabolism, mainly produced by the breakdown of mature red blood cells. Due to its anti-inflammatory, antioxidant, antidiabetic, and antilipemic properties, circulating bilirubin concentrations are inversely associated with the risk of cardiovascular disease, type 2 diabetes, and all-cause mortality in adults. Some genetic loci associated with circulating bilirubin concentrations have been identified by genome-wide association studies in adults. We aimed to examine the relationship between circulating bilirubin, cardiometabolic risk factors, and inflammation in children and adolescents and the genetic architecture of plasma bilirubin concentrations. We measured fasting plasma bilirubin, cardiometabolic risk factors, and inflammatory markers in a sample of Danish children and adolescents with overweight or obesity (n = 1530) and in a population-based sample (n = 1820) of Danish children and adolescents. Linear and logistic regression analyses were performed to analyze the associations between bilirubin, cardiometabolic risk factors, and inflammatory markers. A genome-wide association study (GWAS) of fasting plasma concentrations of bilirubin was performed in children and adolescents with overweight or obesity and in a population-based sample. Bilirubin is associated inversely and significantly with a number of cardiometabolic risk factors, including body mass index (BMI) standard deviation scores (SDS), waist circumference, high-sensitivity C-reactive protein (hs-CRP), homeostatic model assessment for insulin resistance (HOMA-IR), hemoglobin A1c (HbA1c), low-density lipoprotein cholesterol (LDL-C), triglycerides, and the majority of measured inflammatory markers. In contrast, bilirubin was positively associated with fasting plasma concentrations of alanine transaminase (ALT), high-density lipoprotein cholesterol (HDL-C), systolic blood pressure (SDS), and the inflammatory markers GH, PTX3, THBS2, TNFRSF9, PGF, PAPPA, GT, CCL23, CX3CL1, SCF, and TRANCE. The GWAS showed that two loci were positively associated with plasma bilirubin concentrations at a p-value threshold of −8 (rs76999922: β = −0.65 SD; p = 4.3 × 10−8, and rs887829: β = 0.78 SD; p = 2.9 × 10−247). Approximately 25% of the variance in plasma bilirubin concentration was explained by rs887829. The rs887829 was not significantly associated with any of the mentioned cardiometabolic risk factors except for hs-CRP. Our findings suggest that plasma concentrations of bilirubin non-causally associates with cardiometabolic risk factors in children and adolescents

Proton and helium ions acceleration in near-critical density gas targets by short-pulse Ti:Sa PW-class laser

International audienceThe ability to quickly refresh gas-jet targets without cycling the vacuum chamber makes them a promising candidate for laser-accelerated ion experiments at high repetition rate. Here we present results from the first high repetition rate ion acceleration experiment on the VEGA-3 PW-class laser at CLPU. A near-critical density gas-jet target was produced by forcing a 1000 bar H $_2$ and He gas mix through bespoke supersonic shock nozzles. Proton energies up to 2 MeV were measured in the laser forward direction and 2.2 MeV transversally. He $^{2+}$ ions up to 5.8 MeV were also measured in the transverse direction. To help maintain a consistent gas density profile over many shots, nozzles were designed to produce a high-density shock at distances larger than 1 mm from the nozzle exit. We outline a procedure for optimizing the laser–gas interaction by translating the nozzle along the laser axis and using different nozzle materials. Several tens of laser interactions were performed with the same nozzle which demonstrates the potential usefulness of gas-jet targets as high repetition rate particle source.</jats:p