Microwave-induced control of Free Electron Laser radiation

The dynamical response of a relativistic bunch of electrons injected in a planar magnetic undulator and interacting with a counterpropagating electromagnetic wave is studied. We demonstrate a resonance condition for which the free electron laser (FEL) dynamics is strongly influenced by the presence of the external field. It opens up the possibility of control of short wavelength FEL emission characteristics by changing the parameters of the microwave field without requiring change in the undulator's geometry or configuration. Numerical examples, assuming realistic parameter values analogous to those of the TTF-FEL, currently under development at DESY, are given for possible control of the amplitude or the polarization of the emitted radiation.Comment: 14 pages, 5 figures, accepted for publication in Phys. Rev.

Les programmes de recherches de l'axe 3 de la loi du 30 décembre 1991 - Conditionnement et entreposage de longue durée

La loi du 30 décembre 1991 relative à la gestion des déchets à haute activité et à vie longue prévoit un important programme de recherche structuré autour de trois axes : séparation-transmutation, stockage en formation géologique profonde, conditionnement et entreposage de longue durée, apportant une réelle ouverture des options au rendez-vous de 2006, où un rapport global d'évaluation de ces recherches sera adressé au Parlement. L'axe 3 rassemble les études: - Sur la définition de conditionnements et le comportement à long terme des colis pour évaluer leur aptitude vis-à-vis des fonctions essentielles de reprise du colis et de confinement de la radioactivité. - Sur l'entreposage de longue durée, mode de gestion sous la surveillance de la société, protégeant les colis sur une échelle de temps séculaire, garantissant leur reprise dans des conditions sûres et techniquement établies. L'entreposage de longue durée donne une réelle flexibilité à la gestion technique et industrielle du cycle mais n'est pas une solution définitive

Chaos and the taming of free electron laser spectral dynamics

International audienc

Identification of an Exceptionally Long Intron in the HAC1 Gene of Candida parapsilosis

The unfolded protein response (UPR) responds to the build-up of misfolded proteins in the endoplasmic reticulum. The UPR has wide-ranging functions from fungal pathogenesis to applications in biotechnology. The UPR is regulated through the splicing of an unconventional intron in the HAC1 gene. This intron has been described in many fungal species and is of variable length. Until now it was believed that some members of the CTG-Ser1 clade such as C. parapsilosis did not contain an intron in HAC1, suggesting that the UPR was regulated in a different manner. Here we demonstrate that HAC1 plays an important role in regulating the UPR in C. parapsilosis. We also identified an unusually long intron (626 bp) in C. parapsilosisHAC1. Further analysis showed that HAC1 orthologs in several species in the CTG-Ser1 clade contain long introns.The unfolded protein response (UPR) in the endoplasmic reticulum (ER) is well conserved in eukaryotes from metazoa to yeast. The transcription factor HAC1 is a major regulator of the UPR in many eukaryotes. Deleting HAC1 in the yeast Candida parapsilosis rendered cells more sensitive to DTT, a known inducer of the UPR. The deletion strain was also sensitive to Congo red, calcofluor white, and the antifungal drug ketoconazole, indicating that HAC1 has a role in cell wall maintenance. Transcriptomic analysis revealed that treatment of the wild type with DTT resulted in the increased expression of 368 genes. Comparison with mutant cells treated with DTT reveals that expression of 137 of these genes requires HAC1. Enriched GO term analysis includes response to ER stress, cell wall biogenesis and glycosylation. Orthologs of many of these are associated with UPR in Saccharomyces cerevisiae and Candida albicans. Unconventional splicing of an intron from HAC1 mRNA is required to produce a functional transcription factor. The spliced intron varies in length from 19 bases in C. albicans to 379 bases in Candida glabrata, but has not been previously identified in Candida parapsilosis and related species. We used RNA-seq data and in silico analysis to identify the HAC1 intron in 12 species in the CTG-Ser1 clade. We show that the intron has undergone major contractions and expansions in this clade, reaching up to 848 bases. Exposure to DTT induced splicing of the long intron in C. parapsilosisHAC1, inducing the UPR

Daniel Gogny

In this article, the scientific life of D. Gogny is recounted by several collaborators. His strong involvement in researches related to various fields of physics (such as nuclear, atomic and plasma physics as well as electromagnetism) appears clearly, as well as the progresses made in the understanding of fundamental physics

In core instrumentation for online nuclear heating measurements of material testing reactor

International audienceThe present work focuses on nuclear heating. This work belongs to a new advanced research program called IN-CORE which means 'Instrumentation for Nuclear radiations and Calorimetry Online in REactor' between the LCP (University of Provence-CNRS) and the CEA (French Atomic Energy Commission) - Jules Horowitz Reactor (JHR) program. This program started in September 2009 and is dedicated to the conception and the design of an innovative mobile experimental device coupling several sensors and ray detectors for on line measurements of relevant physical parameters (photonic heating, neutronic flux ...) and for an accurate parametric mapping of experimental channels in the JHR Core. The work presented below is the first step of this program and concerns a brief state of the art related to measurement methods of nuclear heating phenomena in research reactor in general and MTR in particular. A special care is given to gamma heating measurements. A first part deals with numerical codes and models. The second one presents instrumentation divided into various kinds of sensor such as calorimeter measurements and gamma ionization chamber measurements. Their basic principles, characteristics such as metrological parameters, operating mode, disadvantages/advantages, ... are discussed