SOLEIL, Gif-sur-Yvette
CNRS/CPT, Marseille
ELETTRA, Basovizza
Università di Firenze, Florence
Université Libre de Bruxelles, Center for Nonlinear Phenomena and Complex Systems - CP 231, Bruxelles
The regime of intensity (and bunching) oscillation following the FEL saturation is investigated using the Colson-Bonifacio model. This regime is understood as an out-of-equilibrium metastable state, which slowly relaxes toward thermodynamical (Boltzmann) equilibrium. This dynamics is also characterized by a strong regularity, unexpected for an interaction between waves and large number of particles, as well as by low-dimensional phase-space structures in the electron-beam phase space. In this context, the switch from regimes associated to high gain (for small electron-beam energy spread) or very low gain (for large energy spread) can be interpreted as out-of-equilibrium phase transitions, a phenomenon which was recently explained by a mechanism of entropy maximization.
SOLEIL, Gif-sur-Yvette
LOA, Palaiseau
ELETTRA, Basovizza
ENEA C.R. Frascati, Frascati (Roma)
In the quest for compact FEL ultra-compact sources, a test experiment is under preparation, to couple an electron beam from a laser driven plasma accelerator, stable and tunable in energy, to an undulator. The electron beam is generated in the colliding laser pulses scheme, by focusing two short and intense laser pulse in an underdense plasma plume. The electron bunch has an energy tunable in up to a few hundreds MeV with 1% energy spread, a length 10 fs, a charge in the 10 pC range, while its radius and divergence are respectively 1μm and 3 mrad. As a first step toward a FEL experiment, the transport and radiation through an undulator of this short and compact electron beam is studied. The spontaneous emission through a 60 cm undulator in the 40-120 nm range is presented, and criteria to reach the threshold of Self-Amplified Spontaneous Emission are discussed.
University of Nova Gorica, Nova Gorica
ELETTRA, Basovizza
The commissioning of the first stage of FERMI@Elettra will start during the summer 2009. During the first year of operation, efforts will concentrate on the optimization of the gun performance, as well as of the electron-beam acceleration and transport through the LINAC. By fall 2010, it is our aim to generate out of the LINAC an electron beam as similar as possible to the one needed for obtaining the nominal (i.e., user-required) FEL performance [see, e.g., S. Di Mitri et al., this Conference]. Such a beam will be then injected into the undulator chain and used to get the first FEL light. In this paper, we present our strategy for the commissioning of the FEL process, both in SASE and seeded configurations. On the basis of start-to-end simulations, we also discuss the expected FEL performance for day-one operation.
ELETTRA, Basovizza
SLAC, Menlo Park, California
University of Nova Gorica, Nova Gorica
Recently, the second FEL line of the FERMI FEL has been modified in order to extend its tuning range down to 3 nm. In order to reach such a short wavelength starting from the UV seed laser the FERMI FEL-2 system relies on a double cascade of high gain harmonic generation. In this work we study the possibility of using the present FEL-2 layout with minor modifications to demonstrate the feasibility of the recently proposed echo-enabled harmonic generation (EEHG). The final aim is to cover the expected spectral range of FEL-2 with a single cascade. The performance of the EEHG in FERMI FEL-2 is estimated by means of start-to-end FEL simulations.
ELETTRA, Basovizza
University of Nova Gorica, Nova Gorica
LBNL, Berkeley, California
The second stage of the FERMI FEL, named FEL-2, is based on the principle of high-gain harmonic generation and relies on a double-seeded cascade. Recent developments stimulated a revision of the original setup, which was designed to cover the spectral range between 40 and 10 nm. According to the numerical simulations we present here, the nominal (expected) electron-beam performance allows to extend the FEL spectral range down to 3 nm. A significant amount of power can be also expected at about 1 nm. We also show that the proposed setup is flexible enough for exploiting future developments of new seed sources, like, e.g., high harmonic generation in gases.
University of Nova Gorica, Nova Gorica
ELETTRA, Basovizza
The commissioning of the first stage of FERMI@Elettra will start during the summer 2009. During the first year of operation, efforts will concentrate on the optimization of the gun performance, as well as of the electron-beam acceleration and transport through the LINAC. By fall 2010, it is our aim to generate out of the LINAC an electron beam as similar as possible to the one needed for obtaining the nominal (i.e., user-required) FEL performance [see, e.g., S. Di Mitri et al., this Conference]. Such a beam will be then injected into the undulator chain and used to get the first FEL light. In this paper, we present our strategy for the commissioning of the FEL process, both in SASE and seeded configurations. On the basis of start-to-end simulations, we also discuss the expected FEL performance for day-one operation.