Polarimétrie harmonique et spectroscopie de photoionisation attoseconde

Attosecond physics is an expending field, intrinsically linked to the High Harmonic Generation process. This emission, which can be either an attosecond pulse train or an isolated attosecond pulse, constitutes a light source in the extreme-UV (XUV) spectral domain, coherent, perfectly synchronous of the generating field. Two thematic have been studied. The first one consists in the complete characterization of the harmonic emission through Molecular Polarimetry, in collaboration with ISMO-Orsay. This technique is based on the measurement of the Molecular Frame PhotoElectron Angular Distribution, during the dissociative ionization of NO molecules. We applied this technique to three configurations producing an elliptically polarized light. For the first time, we obtain the absolute value of the ellipticity, its sign and the depolarization rate. The second topic is the resonant attosecond photoionization: we studied the photoionization of helium, close to the 2s2p autoionization resonance at 60.15 eV, excited by a tunable XUV pulse and probed by an IR pulse, using RABBIT technique, enabling the measurement of the spectral amplitude and phase of the two photons resonant transition. From this, we can reconstruct the two-photons electron wave packets (EWP). These measurements have been completed by simulations done by our collaborator from UAM-Madrid and LCPMR-Paris, showing that, in our experimental conditions, this two photons EWP corresponds to the image of the one-photon EWP. This measurement is the first reconstruction of the temporal dynamic of a resonance non-perturbed by a laser field, with an attosecond resolution.La physique attoseconde est un domaine en pleine expansion, intrinsèquement lié au processus de génération d’harmoniques d’ordre élevé. Cette émission, sous forme d’un train d’impulsions attosecondes ou d’une impulsion attoseconde isolée, constitue une source de lumière dans le domaine spectral extrême-UV (XUV), ultra-brève, cohérente, parfaitement synchrone du champ générateur. Deux thématiques ont été abordées. La première consiste en la caractérisation complète de l’état de polarisation des harmoniques par Polarimétrie Moléculaire en collaboration avec l’ISMO-Orsay. Cette technique est basée sur la mesure de la distribution angulaire des photoélectrons dans le référentiel moléculaire lors de l’ionisation dissociative de la molécule de NO. Nous l’appliquons à trois configurations produisant un rayonnement harmonique polarisé elliptiquement. Nous obtenons ainsi, pour la première fois, la valeur absolue de l’ellipticité harmonique, son signe, ainsi que le taux de dépolarisation.La seconde thématique est la photoionisation attoseconde résonante : nous avons étudié la photoionisation de l’hélium au voisinage de la résonance d'autoionisation 2s2p à 60.15eV, excitée par une impulsion XUV accordable et sondée par une impulsion laser IR en utilisant la technique RABBIT, qui permet la mesure de l’amplitude et de la phase spectrales de la transition résonante à deux photons. Il est ainsi possible de reconstruire dans le domaine temporel, le paquet d'ondes électronique (POE) à 2 photons. Ces mesures ont été complétées par des simulations effectuées par nos collaborateurs à UAM-Madrid et au LCPMR-Paris, qui montrent que, dans nos conditions expérimentales, ce paquet à deux photons est une image fidèle du paquet résonant à un photon. Ceci représente la première reconstruction de la dynamique temporelle d’une résonance non perturbée par le champ laser, avec une résolution attoseconde

Laser wakefield acceleration with high-power, few-cycle mid-IR lasers

The study of laser wakefield electron acceleration (LWFA) using mid-IR laser drivers is a promising path for future laser driven electron accelerators, when compared to traditional near-IR laser drivers operating at 0.8-1 mu m central wavelength (lambda(laser)), as the necessary vector potential (a(0)) for electron injection can be achieved with smaller laser powers due to the linear dependence on lambda(laser). In this work, we perform 2D PIC simulations on LWFA using few-cycle, high power (5-15 TW) laser systems with lambda(laser) ranging from 0.88 to 10 mu m. Such fewcycle systems are currently under development, aiming at Gas High Harmonics Generation applications, where the favorable lambda(2)(laser) scaling extends the range of the XUV photon energies. We keep a(0) and n(e)/n(cr) (n(e) being the plasma density and n(cr) the critical density for each lambda(laser)) as common denominators in our simulations, allowing for comparisons between drivers with different lambda(laser), with respect to the accelerated electron beam energy, charge and conversion efficiency. While the electron energies are mainly dominated by the plasma dynamics, the laser to electron beam energy conversion efficiency shows significant enhancement with longer wavelength laser drivers. (c) 2018 Elsevier B.V. All rights reserved

Tracking ultrafast solid-state dynamics using high harmonic spectroscopy

WWe establish time-resolved high harmonic generation (tr-HHG) as a powerful spectroscopy method for tracking photoinduced dynamics in strongly correlated materials through a detailed investigation of the insulator-to-metal phase transitions in vanadium dioxide. We benchmark the technique by comparing our measurements to established momentum-resolved ultrafast electron diffraction, and theoretical density functional calculations. Tr-HHG allows distinguishing of individual dynamic channels, including a transition to a thermodynamically hidden phase. In addition, the HHG yield is shown to be modulated at a frequency characteristic of a coherent phonon of the equilibrium monoclinic phase over a wide range of excitation fluences. These results demonstrate that tr-HHG is capable of tracking complex dynamics in solids through its sensitivity to the band structure

Tracking ultrafast solid-state dynamics using high harmonic spectroscopy

We establish time-resolved high harmonic generation (tr-HHG) as a powerful spectroscopy for photoinduced dynamics in strongly correlated materials through a detailed investigation of the insulator-to-metal transitions in vanadium dioxide. We benchmark our technique by comparing our measurements to established momentum-resolved ultrafast electron diffraction, and theoretical density functional calculations. Tr-HHG allows distinguishing of individual dynamic channels, including a transition to a thermodynamically hidden phase. In addition, the HHG yield is shown to be modulated at a frequency characteristic of a coherent phonon in the equilibrium monoclinic phase over a wide range of excitation fluences. These results demonstrate that tr-HHG is capable of tracking complex dynamics in solids through its sensitivity to the band structure.Comment: 20 pages and 4 figures main text, 8 pages and 4 figures supplementary informatio

Patient blood management in Europe

Preoperative anaemia is common in patients undergoing orthopaedic and other major surgery. Anaemia is associated with increased risks of postoperative mortality and morbidity, infectious complications, prolonged hospitalization, and a greater likelihood of allogeneic red blood cell (RBC) transfusion. Evidence of the clinical and economic disadvantages of RBC transfusion in treating perioperative anaemia has prompted recommendations for its restriction and a growing interest in approaches that rely on patients' own (rather than donor) blood. These approaches are collectively termed ‘patient blood management’ (PBM). PBM involves the use of multidisciplinary, multimodal, individualized strategies to minimize RBC transfusion with the ultimate goal of improving patient outcomes. PBM relies on approaches (pillars) that detect and treat perioperative anaemia and reduce surgical blood loss and perioperative coagulopathy to harness and optimize physiological tolerance of anaemia. After the recent resolution 63.12 of the World Health Assembly, the implementation of PBM is encouraged in all WHO member states. This new standard of care is now established in some centres in the USA and Austria, in Western Australia, and nationally in the Netherlands. However, there is a pressing need for European healthcare providers to integrate PBM strategies into routine care for patients undergoing orthopaedic and other types of surgery in order to reduce the use of unnecessary transfusions and improve the quality of care. After reviewing current PBM practices in Europe, this article offers recommendations supporting its wider implementation, focusing on anaemia management, the first of the three pillars of PBM

Eltrombopag for myelodysplastic syndromes or chronic myelomonocytic leukaemia with no excess blasts and thrombocytopenia: a French multicentre retrospective real-life study.

peer reviewedDespite a moderate prevalence in low-risk myelodysplastic syndromes (MDS) and chronic myelomonocytic leukaemia (CMML), thrombocytopenia remains a risk of severe bleeding and therapeutic options are still limited. There are only a few studies with eltrombopag (ELT), a thrombopoietin receptor agonist, in those patients. In this retrospective multicentre study, ELT was used in 50 patients with MDS and 11 with CMML, with no excess of marrow blasts and platelet counts of <50 × 109 /l in a 'real-life' situation. Platelet response occurred in 47 (77%) patients. The median (range) duration of response was 8 (0-69) months. None of the eight still responders who discontinued ELT had relapsed, at a median (range) of 16 (6-23) months after ELT discontinuation. Although 36% of the patients were anti-coagulated or anti-aggregated only 10% of patients had Grade ≥3 bleeding events. Thrombotic events were observed in six (10%) patients, who all but one had a medical history of arterial or venous thrombosis. Progression to acute myeloid leukaemia occurred in four (7%) patients. In this first 'real-life' study, ELT was effective and generally well tolerated in patients with MDS/CMML without excess blasts

Open Data from the Third Observing Run of LIGO, Virgo, KAGRA, and GEO

The global network of gravitational-wave observatories now includes five detectors, namely LIGO Hanford, LIGO Livingston, Virgo, KAGRA, and GEO 600. These detectors collected data during their third observing run, O3, composed of three phases: O3a starting in 2019 April and lasting six months, O3b starting in 2019 November and lasting five months, and O3GK starting in 2020 April and lasting two weeks. In this paper we describe these data and various other science products that can be freely accessed through the Gravitational Wave Open Science Center at https://gwosc.org. The main data set, consisting of the gravitational-wave strain time series that contains the astrophysical signals, is released together with supporting data useful for their analysis and documentation, tutorials, as well as analysis software packages