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

An optimized architecture of a digital filtering integrated procesor, and efficiency graphical valuation

This paper deals with the optimization of a digital signal processor's architecture. We define the notion of silicon area temporal utilization efficiency and calculate it with a graphie method . Using benchmark algorithm (Fast Fourier Transform butterfly) we estimate the influence of an architecture choice on its efficiency . In this manner we can objectively measure the contribution of the multifarious modifications .Conception d'un processeur pour filtrage numérique et optimisation de son architecture. Définition de la notion de rendement temporel d'utilisation de la surface de silicium, mesure par méthode graphique. A partir du choix d'une jauge d'algorithme, le papillon de la transformée de Fourier rapide on évalue l'influence de tel choix d'architecture sur les performances et le rendement. On essaye de valider la structure indépendamment de la technologi

Synchrotron radiation-based experimental determination of the optimal energy for cell radiotoxicity enhancement following photoelectric effect on stable iodinated compounds

This study was designed to experimentally evaluate the optimal X-ray energy for increasing the radiation energy absorbed in tumours loaded with iodinated compounds, using the photoelectric effect. SQ20B human cells were irradiated with synchrotron monochromatic beam tuned at 32.8, 33.5, 50 and 70 keV. Two cell treatments were compared to the control: cells suspended in 10 mg ml1 of iodine radiological contrast agent or cells pre-exposed with 10 mM of iodo-desoxyuridine (IUdR) for 48 h. Our radiobiological end point was clonogenic cell survival. Cells irradiated with both iodine compounds exhibited a radiation sensitisation enhancement. Moreover, it was energy dependent, with a maximum at 50 keV. At this energy, the sensitisation calculated at 10% survival was equal to 2.03 for cells suspended in iodinated contrast agent and 2.60 for IUdR. Cells pretreated with IUdR had higher sensitisation factors over the energy range than for those suspended in iodine contrast agent. Also, their survival curves presented no shoulder, suggesting complex lethal damages from Auger electrons. Our results confirm the existence of the 50 keV energy optimum for a binary therapeutic irradiation based on the presence of stable iodine in tumours and an external irradiation. Monochromatic synchrotron radiotherapy concept is hence proposed for increasing the differential effect between healthy and cancerous tissue irradiation

Theoretical approach based on Monte-Carlo simulations to predict the cell survival following BNCT

International audienceWe present here a very preliminary work on BNCT Dosimetry. The approach is as follows:A full Monte Carlo calculation is used to separate all dose components and determine the corresponding physical dose fractions with a realistic clinical model.These dose fractions are then used as mixed fields to predict cell-survivals and RBE values for a specific cell-line, thanks to the radiobiological model NanOxTM

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

Coherence properties of focused X-ray beams at high-brilliance synchrotron sources

An analytical approach describing properties of focused partially coherent X-ray beams is presented. The method is based on the results of statistical optics and gives both the beam size and transverse coherence length at any distance behind an optical element. In particular, here Gaussian Schell-model beams and thin optical elements are considered. Limiting cases of incoherent and fully coherent illumination of the focusing element are discussed. The effect of the beam-defining aperture, typically used in combination with focusing elements at synchrotron sources to improve transverse coherence, is also analyzed in detail. As an example, the coherence properties in the focal region of compound refractive lenses at the PETRA III synchrotron source are analyzed

Undulators and wigglers for the new generation of synchrotron sources

The technological issues involved in the manufacturing of undulators and wigglers for the new generation of synchrotron radiation sources are discussed, with a particular emphasis on the solutions adopted at ESRF such as segmentation and shimming. The main characteristics of the radiation from the undulators and wigglers are discussed in term of total power, angular power, spectral brilliance and spectral flux. Illustration is again taken from ESRF. A brief description is given of the new devices that have been or can be, built to produce circularly polarized radiation

OPTICAL KLYSTRONS

Le klystron optique est une version modifiée de l'onduleur utilisé pour améliorer le gain du Laser à Electrons Libres. L'émission spontanée et le gain sont calculés en fonction de l'énergie des électrons et de la longueur d'onde. Quelques effets limitant l'augmentation du gain sont étudiés : dispersion en énergie, dispersion angulaire, tailles transverses du faisceau d'électrons. Je discute brièvement l'utilisation de la modulation en densité introduite par le klystron optique sur le faisceau d'électrons pour générer du rayonnement synchrotron cohérent.The Optical Klystron is a modification of the undulator which can be used to improve the gain in a Free Electron Laser. Spontaneous emission and gain are theoretically studied as function of electron energy and wavelength. Several effects limiting the gain enhancement are calculated : energy spread, angular spread, beam dimensions. I briefly discuss how one can use the electron beam bunching generated by the Optical Klystron to emit coherent synchrotron radiation