ARC-EN-CIEL beam dynamics

MOPC023International audienceARC-EN-CIEL project is based on a CW 1.3 GHz superconducting (SC) linac accelerator delivering high charge, subpicosecond and low emittance electron bunches at high repetition rate [1]. According to the electron energy, it provides tunable light sources of high brightness in the VUV to soft X-ray wavelength domain. The project will evolve into three phases: first and second phases are based on high brightness single pass SC linac configuration with a low average current (few µA), while third phase integrates recirculation loops to increase the average current (up to 100 mA)

Chaos in free electron laser oscillators

The chaotic nature of a storage-ring Free Electron Laser (FEL) is investigated. The derivation of a low embedding dimension for the dynamics allows the low-dimensionality of this complex system to be observed, whereas its unpredictability is demonstrated, in some ranges of parameters, by a positive Lyapounov exponent. The route to chaos is then explored by tuning a single control parameter, and a period-doubling cascade is evidenced, as well as intermittence.Comment: Accepted in EPJ

The ThomX project status

Work supported by the French Agence Nationale de la recherche as part of the program EQUIPEX under reference ANR-10-EQPX-51, the Ile de France region, CNRS-IN2P3 and Université Paris Sud XI - http://accelconf.web.cern.ch/AccelConf/IPAC2014/papers/wepro052.pdfA collaboration of seven research institutes and an industry has been set up for the ThomX project, a compact Compton Backscattering Source (CBS) based in Orsay - France. After a period of study and definition of the machine performance, a full description of all the systems has been provided. The infrastructure work has been started and the main systems are in the call for tender phase. In this paper we will illustrate the definitive machine parameters and components characteristics. We will also update the results of the different technical and experimental activities on optical resonators, RF power supplies and on the electron gun

Lasers à électrons libres de courtes longueurs d'onde : état de l'art et perspectives

Les Lasers à Électrons Libres (LEL) sont des sources de rayonnement cohérent et accordable, basées sur l'interaction d'un faisceau d'électrons relativistes circulant dans le champ magnétique magnétique périodique et permanent créé par un “onduleur”. et d'une onde optique. L'onde lumineuse peut être issue de l'émission de rayonnement synchroton émise par le paquet d'électrons a chaque passage pour un système super-radiant en mode SASE (Self Amplified Spontaneous Emission- Emission Spontanée Auto-Amplifiée) ou issue du rayonnement synchrotron stocké dans une cavité optique, en mode oscillateur, ou d'une onde laser externe, en mode génération d'harmonique. Sous certaines conditions, l'onde lumineuse est amplifiée, au détriment de l'énergie cinétique des électrons, ce qui conduit à l'effet laser. L'état de l'art des sources Laser à Electrons Libres dans l'UV et le VUV est présenté, en indiquant les complémentarités résultant des différentes configurations tant du point de vue des sources que de leurs utilisations. Les projets de sources de courte longueur d'onde proposés sont ensuite discutés.

Lasers UV à électrons libres

Les Lasers à Électrons Libres (LEL) sont des sources cohérentes, accordables, de puissance moyenne élevée et de durée picoseconde. Les LELs couvrent, actuellement, une vaste gamme spectrale allant des ondes millimétriques au VUV. Dans le domaine UV-VUV-X, les LELs sont implantés sur des accélérateurs linéaires ou sur des anneaux de stockage. L'état de l'art du point de vue des performances est ici brossé

The super-ACO free electron laser in the UV, first application for time-resolved fluorescence in biology and prospects for soleil

Storage ring (SR) Free Electron Lasers (FEL) are very promising tunable laser sources in the UV. The Super-ACO UV FEL at 800 MeV was recently improved : enhanced power (roughly two orders of magnitude higher compared to other FELs), 10 hours duration per beam injection, long-term stability, 60 ps FWHM micropulses repeated at 8 MHz, generally CW at the ms range.This source was first successfully used at 350 nm : polarized fluorescence decays of the reduced nicotinamide adenine dinucleotide coenzyme in aqueous solution were recorded versus temperature, using the single photon counting technique, leading to accurate measurements and original results, thus demonstrating the quality of the Super-ACO FEL. Moreover, SRFELs appear as unique tools in various scientific fields for two-colours experiments, coupling both the UV FEL and synchrotron radiation, naturally synchronized. Projects are underway on Super-ACO. However, the small gain achieved on the Super-ACO FEL limits its performances such as tunability, short wavelength operation. A FEL implantation on SOLEIL will offer a powerful tunable source between 350 and 100 nm together with synchrotron radiation. Rather than a single by-pass, an efficient solution with two longer straight sections seems more attractive

Pulse Splitting in Short Wavelength Seeded Free Electron Lasers

We investigate a fundamental limitation occurring in vacuum ultraviolet and extreme ultraviolet seeded free electron lasers (FELs). For a given electron beam and undulator configuration, an increase of the FEL output energy at saturation can be obtained via an increase of the seed pulse duration. We put in evidence a complex spatiotemporal deformation of the amplified pulse, leading ultimately to a pulse splitting effect. Numerical studies of the Colson-Bonifacio FEL equations reveal that slippage length and seed laser pulse wings are core ingredients of the dynamics