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Title |
Page |
| MOPPH025 |
Free Electron Laser as Paradigmatic Example of Systems with Long-Range Interactions
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87 |
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- D. Fanelli, A. Antoniazzi, S. Ruffo
Università di Firenze, Florence
- J. Barre'
Université de Nice Sophia-Antipolis, Nice
- T. Dauxois
ENS LYON, Lyon
- G. De Ninno
ELETTRA, Basovizza, Trieste
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Long range interactions are such that the two-body interaction potential decreases at large distance with a power which is smaller or equal to the space dimension. Examples include gravitational forces, unshielded Coulombic interaction. In presence of long-range interactions, physics is very peculiar and a wide range of striking phenomena appears. In particular energy is non additive, hence the system under scrutiny cannot be divided into independent macroscopic parts, as it is usually the case for short-range interactions. These unexpected features are systematically detected, independently of the specific nature of the long-range interactions involved. FEL are one of the most interesting examples of systems with long-range interactions, where the interplay between collective (wave) and individual (particles) degrees of freedom is well known to be central and, in this respect, provides a unique experimental ground to investigate such universal pecularities. In this presentation I will review the main characteristics of such systems and dicuss the statistical theory of the Vlasov equation, a wide general approach that enables to analytically investigate the laser saturated regime.
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| MOPPH031 |
The Saturated Regime of a Seeded Single-Pass Free Electron Laser: a Theoretical Investigation through the Statistical Mechanics of the Vlasov Equation
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103 |
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- F. Curbis, F. Curbis
Università degli Studi di Trieste, Trieste
- A. Antoniazzi, D. Fanelli
Università di Firenze, Florence
- G. De Ninno
ELETTRA, Basovizza, Trieste
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The quasi-stationary state characterizing the saturation of a single-pass free-electron laser is governed by the Vlasov equation obtained by performing the continuum limit of the Colson-Bonifacio model. By means of a statistical treatment, this approach allows to predict analytically the saturated laser intensity as well as the final electron-beam energy distribution. In this paper we consider the case of coherent harmonic generation obtained from a seeded free-electron laser and present predictions for the first stage of the project FERMI at Elettra project at Sincrotrone Trieste.
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| MOPPH055 |
Coherent Harmonic Emission of the Elettra Storage-Ring Free-Electron Laser in Single-Pass Configuration: a Numerical Study for Different Undulator Polarizations
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170 |
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- F. Curbis, F. Curbis
Università degli Studi di Trieste, Trieste
- G. De Ninno
ELETTRA, Basovizza, Trieste
- H. Freund
SAIC, McLean
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The optical klystron installed on the Elettra storage-ring is normally used as interaction region for an oscillator free-electron laser, but, removing the optical cavity and using an external seed laser, one obtains an effective scheme for the single-pass harmonic generation. In this configuration, which is presently under development, the high-power external laser is synchronized with the electron beam entering the first undulator of the optical klystron. The laser-electron beam interaction produces a spatial partition of electrons in micro-bunches separated by the seed wavelength. The micro-bunching is then exploited in the second undulator (radiator) to produce coherent light at the harmonics of the seed wavelength. The Elettra radiator is an APPLE type undulator and this allows to explore different configurations of polarization. We present here numerical results obtained using the code Medusa for both planar and helical configurations. We also draw a comparison with predictions of the numerical code Genesis.
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| MOPPH057 |
Design and Performance of the FERMI at Elettra FEL
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174 |
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- G. De Ninno, E. Allaria
ELETTRA, Basovizza, Trieste
- W. M. Fawley, G. Penn
LBNL, Berkeley, California
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The FERMI project* at Sincrotrone Trieste is the first user facility based on seeded, harmonic cascade FELs. The second stage FEL will produce tunable output in the 10-40nm wavelength range and will rely upon two stages of harmonic up-conversion. A major goal for this FEL is good longitudinal output coherence (i.e., small spectral bandwidth). At present, we are examining the performance characteristics of two possible configurations. The first "fresh bunch" option is a classic harmonic cascade, where the output radiation from the first radiator is used to seed a fresh part of the electron bunch in the second-stage modulator. The second "whole bunch" scheme seeds the entire e-beam pulse, uses a much shorter first radiator and completely eliminates the second modulator, with the second radiator involving many e-folds of gain. Relying both upon time-steady input parameter sensitivity studies and full start-to-end time-dependent simulations**, we examine the predicted performance of the two configurations and compare with users requirements.
* C. Bocchetta et al., this meeting ** S. Di Mitri et al., this meeting
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| MOPPH058 |
Start-to-end Time-Dependent Study of FEL Output Sensitivity to Electron-beam Jitters for the First Stage of the FERMI@Elettra Project
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178 |
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- G. De Ninno, E. Allaria, M. Trovo
ELETTRA, Basovizza, Trieste
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Sensitivity of the output laser pulse to electron-beam jitters is one of the major issues affecting the expected performance of both SASE and seeded FEL's. Focusing on the first stage of the FERMI@Elettra project, in this paper we present results of time-dependent numerical simulations in which the codes GENESIS and GINGER have been used to process a large number of electron-beam distributions generated at the gun using the code GPT and propagated through the linac using the code ELEGANT.
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| MOCAU02 |
The Challenges of Seeded FELs
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233 |
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- G. De Ninno
ELETTRA, Basovizza, Trieste
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Basic users' expectations for the light produced by next generation FELs are:- much higher peak brilliance than conventional synchrotron radiation and complete tunability in the VUV/X-ray spectral range;
- full transverse and longitudinal coherence of the radiation pulse;
- possibility of controlling pulse duration and spectral bandwidth;
- high shot-to-shot reproducibility, i.e. low power fluctuations, good pointing stability and reduced temporal jitter.
Seeded schemes appear nowadays as a way to satisfy all the above mentioned requirements. However, this achievement relies on the solution of several open technological and physical issues. In this paper we give a review of some of these challenges and discuss the expected performance of future seed-based FELs.
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Slides
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Talk
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| TUPPH020 |
Dynamics Control of the Elettra Storage Ring Free-Electron Laser with Digital Feedbacks
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356 |
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- E. Allaria, G. De Ninno
ELETTRA, Basovizza, Trieste
- A. Antoniazzi, D. Fanelli
Università di Firenze, Florence
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The laser dynamics of a storage-ring free-electron laser (FEL) has two main sources of instabilities. First of all, as it is known, dynamical instabilities are developed as the FEL is moved away from the exact tuning between the period of the electron bunch(es) circulating into the ring and that of the photon pulse stored in the optical cavity. In addition, external (low-frequency) noise sources have a strong influence on the dynamical behaviour of the system and can perturb its dynamic. Different feedback techniques have been proposed in order to control dynamical instabilities and stabilize the FEL output. We present here a numerical and experimental investigation on the control of the Elettra SRFEL dynamics using the simultaneous combination of different feedbacks techniques that have been experimentally implemented by means of a Field ProgrammableGate Aarray (FPGA).
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| TUPPH021 |
Q-Switch Techniques Implemented at the ELETTRA Storage-Ring Free Electron Laser
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360 |
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- F. Curbis, F. Curbis
Università degli Studi di Trieste, Trieste
- M. B. Danailov, G. De Ninno, B. Diviacco, L. Romanzin, M. Trovo
ELETTRA, Basovizza, Trieste
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In a storage-ring FEL the gain can be calculated measuring the rise-time of giant pulses, produced by the interaction between the light stored in the optical cavity and an electron beam with low energy-spread (cold beam). This interplay produces the heating of the beam. Therefore, after the generation of a single giant pulse, the overlap between electrons and radiation is periodically prevented for a time necessary to dump the energy spread and recover the cold-beam condition. For this purpose two different methods are implemented at Elettra. In the first, modifying the radio-frequency of the ring, the change of the revolution time of electrons avoids the temporal overlap between the electron beam and the optical field in the mirror cavity. The second method relies on a mechanical gating (chopper) which intercept the light produced during previous interactions, inducing a periodic emptying of the optical cavity. The gain can be also estimated using an indirect formula after measuring the electron-beam energy spread and bunch length. In this paper we compare the different techniques mentioned above for the case of the Elettra SR-FEL.
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| MOPPH054 |
FERMI @ Elettra: A Seeded FEL Facility for EUV and Soft X-Rays
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166 |
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- J. N. Corlett, L. R. Doolittle, W. M. Fawley, S. M. Lidia, G. Penn, I. V. Pogorelov, J. Qiang, A. Ratti, J. W. Staples, R. B. Wilcox, A. Zholents
LBNL, Berkeley, California
- E. Allaria, C. J. Bocchetta, D. Bulfone, F. C. Cargnello, D. Cocco, P. Craievich, G. D'Auria, M. B. Danailov, G. De Ninno, S. Di Mitri, B. Diviacco, M. Ferianis, A. Galimberti, A. Gambitta, M. Giannini, F. Iazzourene, E. Karantzoulis, M. Lonza, F. M. Mazzolini, G. Penco, L. Rumiz, S. Spampinati, G. Tromba, M. Trovo, A. Vascotto, M. Veronese, M. Zangrando
ELETTRA, Basovizza, Trieste
- M. Cornacchia, P. Emma, Z. Huang, J. Wu
SLAC, Menlo Park, California
- W. Graves, F. X. Kaertner, D. Wang
MIT, Middleton, Massachusetts
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We describe the conceptual design and major performance parameters for the FERMI FEL project funded for construction at the Sincrotrone Trieste, Italy. This user facility complements the existing storage ring light source at Sincrotrone Trieste, and will be the first facility to be based on seeded harmonic cascade FELs. Seeded FELs provide high peak-power pulses, with controlled temporal duration of the coherent output allowing tailored x-ray output for time-domain explorations with short pulses of 100 fs or less, and high resolution with output bandwidths of the order of meV. The facility uses the existing 1.2 GeV S-band linac, driven by electron beam from a new high-brightness rf photocathode gun, and will provide tunable output over a range from ~100 nm to ~10 nm, and APPLE undulator radiators allow control of x-ray polarization. Initially, two FEL cascades are planned, a single-stage harmonic generation to operate over ~100 nm to ~40 nm, and a two-stage cascade operating from ~40 nm to ~10 nm or shorter wavelengh, each with spatially and temporally coherent output, and peak power in the GW range.
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| TUPPH044 |
Free Electron Laser Study of Free Carbon Clusters
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423 |
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- C. Spezzani, E. Allaria, F. Curbis, G. De Ninno, B. Diviacco, L. Romanzin, S. Tileva, M. Trovo
ELETTRA, Basovizza, Trieste
- M. Amati, G. Bongiorno, C. Lenardi, T. Mazza, P. Milani, T. A. Mostefaoui, P. Piseri, L. Ravagnan
Università degli Studi di Milano, Milano
- M. Coreno
CNR - IMIP, Trieste
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UV absorption from carbon nanoparticles is a very interesting astrophysical topic. The prominent hump centered at 217.5nm is the most dominant feature in the interstellar extinction curve and also the most controversial and a long-standing problem in astrophysics. Actual models lack of experimental data about carbon dust in gas phase. At the University of Milano an experimental set-up based on a PulsedμPlasma Source has been developed for the investigation of free clusters at the Elettra Gas Phase beamline (CESyRA: Cluster Experiments with Synctrotron RAdiation). The cluster source produces very intense cluster beams with tunable size distribution. The design of the apparatus is extended with a chamber for gas phase reaction (water vapor, CO, H2…) providing a unique opportunity to study the gas phase properties of carbonaceous particles in different environment. We plan to investigate Resonant Raman scattering of free carbon particles tuning the high brilliance UV/VIS storage ring FEL of ELETTRA across the region of 217nm where the UV absorption hump in astrophysical data is observed and where a number of electronic transitions exist for variable size linear carbon chains.
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