Dipole Fringe Field Effects in the ThomX Ring

WEPEA003 - work is supported by the French "Agence Nationale de la Recherche" as part of the program "investing in the future" under reference ANR-10-EQPX-51, and also by grants from Region Ile-de-France.International audienceThom-X is a 50MeV compact ring based on the Compton back-scattering which is being built in LAL, France. With a very short bend radius of 0.352 m, the nonlinear effects of the dipole fringe fields become critical to the beam dynamic . This paper compares the modelings of the dipole fringe field using four popular codes: MadX, Elegant, BETA, and Tracy3, and then discuss the proper model to have consistent results between the analytical calculation and the symplectic tracking of the Thom-X ring

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)

Effect of Beam Dynamics Processes in the Low Energy Ring ThomX

As part of the R\&D for the 50 MeV ThomX Compton source project, we have studied the effect of several beam dynamics processes on the evolution of the beam in the ring. The processes studied include among others Compton scattering, intrabeam scattering, coherent synchrotron radiation. We have performed extensive simulations of a full injection/extraction cycle (400000 turns). We show how each of these processes degrades the flux of photons produced and how a feedback system contributes to recovering most of the flux.Comment: Submitted to IPAC'14, WEPRO00

Electron Beam Dynamics in the 50 MeV ThomX Compact Storage Ring

International audienceThomX is a high flux compact X-ray source based on Compton back scattering between a relativistic electron beam and an intense laser pulse. To increase the repetition rate, the electron beam is stored in a ring. The main drawback of such a scheme is the low energy of the electrons regarding collective effects and intrabeam scattering. These effects tend to enlarge or even disrupt the stored bunch and they limit its charge, especially in a system where damping plays a negligible role. Thus such collective effects reduce the maximum X-ray flux and it is important to investigate them to predict the performance of this type of X-ray source. In addition, the Compton back scattering acts on the electron beam by increasing its energy spread. This presentation will show firstly the impact of collective effects on the electron beam, essentially during the first turns when they are the most harmful. Then, the reduction of the X-ray flux due to Compton back scattering and intrabeam scattering will be investigated on a longer time scale

Simulations and Studies of Electron Beam Dynamics under Compton Back-scattering for the Compact X-ray Source ThomX

MOPWO004 - ISBN 978-3-95450-122-9International audienceIn this article are presented beam dynamics investiga- tions of a relativistic electron bunch in the compact storage ring ThomX (50 MeV), which is under construction at LAL to produce hard X-ray using Compton Back-Scattering (CBS). The effect of CBS has been implemented in a 6D tracking code. In addition to CBS, the influence of lattice non linearities and various collective effects on the flux of scattered Compton photons is investigated

Compact Ring for the ThomX-ray Source

THPE060International audienceOne advantage of X-ray sources based on Compton Back Scattering (CBS) processes is that such compact machines can produce an intense flux of monochromatic X-rays. CBS results from collisions between laser pulses and relativistic electron bunches. Aiming at high X-ray flux, one possible configuration combining a low emittance linear accelerator with a compact storage ring and a high gain laser cavity has been adopted by the ThomX project. We present here the main ring lattice characteristics in terms of baseline optics, possible other tunings such as low or negative momentum compaction, and orbit correction schemes. In addition, non-linear beam dynamics aspects including fringe field components as well as higher multipole tolerances are presented

The Transparency of Solar Coronal Active Regions

Resonance scattering has often been invoked to explain the disagreement between the observed and predicted line ratios of Fe XVII 15.01 A to Fe XVII 15.26 A (the ``3C/3D'' ratio). In this process photons of 15.01, with its much higher oscillator strength, are preferentially scattered out of the line of sight, thus reducing the observed line ratio. Recent laboratory measurements, however, have found significant inner-shell Fe XVI lines at 15.21 and 15.26 Angstroms, suggesting that the observed 3C/3D ratio results from blending. Given our new understanding of the fundamental spectroscopy, we have re-examined the original solar spectra, identifying the Fe XVI 15.21 line and measuring its flux to account for the contribution of Fe XVI to the 15.26 flux. Deblending brings the 3C/3D ratio into good agreement with the experimental ratio; hence, we find no need to invoke resonance scattering. Low opacity in Fe XVII 15.01 also implies low opacity for Fe XV 284.2, ruling out resonance scattering as the cause of the fuzziness of TRACE and SOHO EIT 284-Angstrom images. The images must, instead, be unresolved due to the large number of structures at this temperature. Insignificant resonance scattering implies that future instruments with higher spatial resolution could resolve the active region plasma into its component loop structures.Comment: accepted to Ap J Letter