11 research outputs found
X-ray amplification from a Raman Free Electron Laser
accepted for publication in Phys. Rev. Lett. 03/11/2012We demonstrate that a mm-scale free electron laser can operate in the X-ray range, in the interaction between a moderately relativistic electron bunch, and a transverse high intensity optical lattice. The corrugated light-induced ponderomotive potential acts simultaneously as a guide and as a low-frequency wiggler, triggering stimulated Raman scattering. The gain law in the small signal regime is derived in a fluid approach, and confirmed from Particle-In-Cell simulations. We describe the nature of bunching, and discuss the saturation properties. The resulting all-optical Raman X-ray laser opens perspectives for ultra-compact coherent light sources up to the hard X-ray range
Impact of cardiac resynchronization therapy optimization inside a heart failure programme : a realâworld experience
Aims: This study sought to describe and evaluate the impact of a routine inâhospital cardiac resynchronization therapy (CRT) programme, including comprehensive heart failure (HF) evaluation and systematic echoâguided CRT optimization. Methods and results: CRT implanted patients were referred for optimization programme at 3 to 12 months from implantation. The program included clinical and biological status, standardized screening for potential cause of CRT nonâresponse and systematic echoâguided atrioventricular and interventricular delays (AVd and VVd) optimization. Initial CRTâresponse and improvement at 6 months postâoptimization were assessed with a clinical composite score (CCS). Major HF events were tracked during 1 year after optimization. A total of 227 patients were referred for CRT optimization and enrolled (71 ± 11 years old, 77% male, LVEF 30.6 ± 7.9%), of whom 111 (48.9%) were classified as initial nonâresponders. Left ventricular lead dislodgement was noted in 4 patients (1.8%), and loss or â€90% biventricular capture in 22 (9.7%), mostly due to arrhythmias. Of the 196 patients (86%) who could undergo echoâguided CRT optimization, 71 (36.2%) required VVd modification and 50/144 (34.7%) AVd modification. At 6 months postâoptimization, 34.3% of the initial nonâresponders were improved according to the CCS, but neither AVd nor VVd echoâguided modification was significantly associated with CCSâimprovement. After oneâyear followâup, initial nonâresponders maintained a higher rate of major HF events than initial responders, with no significant difference between AVd/VVd modified or not. Conclusions: Our study supports the necessity of a close, comprehensive and multidisciplinary followâup of CRT patients, without arguing for routine use of echoâguided CRT optimization
Innovative Education and Training in high power laser plasmas (PowerLaPs) for plasma physics, high power laser-matter interactions and high energy density physics - Theory and experiments
The Erasmus Plus programme 'Innovative Education and Training in high power laser plasmas', otherwise known as PowerLaPs, is described. The PowerLaPs programme employs an innovative paradigm in that it is a multi-centre programme where teaching takes place in five separate institutes with a range of different aims and styles of delivery. The 'in class' time is limited to four weeks a year, and the programme spans two years. PowerLaPs aims to train students from across Europe in theoretical, applied and laboratory skills relevant to the pursuit of research in laser-plasma interaction physics and inertial confinement fusion (ICF). Lectures are intermingled with laboratory sessions and continuous assessment activities. The programme, which is led by workers from the Technological Educational Institute (TEI) of Crete, and supported by co-workers from the Queen's University Belfast, the University of Bordeaux, the Czech Technical University in Prague, Ecole Polytechnique, the University of Ioannina, the University of Salamanca and the University of York, has just completed its first year. Thus far three Learning Teaching Training (LTT) activities have been held, at the Queen's University Belfast, the University of Bordeaux and the Centre for Plasma Physics and Lasers (CPPL) of TEI Crete. The last of these was a two-week long Intensive Programme (IP), while the activities at the other two universities were each five days in length. Thus far work has concentrated upon training in both theoretical and experimental work in plasma physics, high power laser-matter interactions and high energy density physics. The nature of the programme will be described in detail and some metrics relating to the activities carried out to date will be presented
Gravitational influence of high power laser pulses
The study of gravitational wave generation in the laboratory presents an opportunity to observe and understand more easily the mechanisms at work in gravitation. The present study will focus on the gravitational deformation generated by a light pulse, as it could be generated by a current ultra-high power laser. Although of very small magnitude, the deformation thus generated has advantages over that generated by mass acceleration, and could therefore prove useful in the long-term establishment of a laboratory experiment for the generation and detection of gravitational waves
X-ray amplification from a Raman Free Electron Laser
We demonstrate that a mm-scale free electron laser can operate in the X-ray range, in the interaction between a moderately relativistic electron bunch, and a transverse high intensity optical lattice. The corrugated light-induced ponderomotive potential acts simultaneously as a guide and as a low-frequency wiggler, triggering stimulated Raman scattering. The gain law in the small signal regime is derived in a fluid approach, and confirmed from Particle-In-Cell simulations. We describe the nature of bunching, and discuss the saturation properties. The resulting all-optical Raman X-ray laser opens perspectives for ultra-compact coherent light sources up to the hard X-ray range
Asymptotic-preserving numerical scheme for the electronic M1 model in the diffusive limit
International audienc
Modeling of radiative and quantum electrodynamics effects in PIC simulations of ultra-relativistic laser-plasma interaction
International audienc