| Paper | Title | Page |
|---|---|---|
| MOPPH057 | Design and Performance of the FERMI at Elettra FEL | 174 |
|
||
|
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 |
||
| MOPPH073 | An Enhanced GINGER Simulation Code with Harmonic Emission and HDF5 IO Capabilities | 218 |
|
||
|
GINGER* is an axisymmetric, polychromatic (r-z-t) FEL simulation code originally developed in the mid-1980's to model the performance of single-pass amplifiers. Over the past 15 years GINGER's capabilities have been extended to include more complicated configurations such as undulators with drift spaces, dispersive sections, and vacuum chamber wakefield effects; multi-pass oscillators; and multi-stage harmonic cascades. Its coding base has been tuned to permit running effectively on platforms ranging from desktop PC's to massively parallel processors such as the IBM-SP. Recently, we have made significant changes to GINGER by replacing the original predictor-corrector field solver with a new direct implicit algorithm, adding harmonic emission capability, and switching to the HDF5 IO library** for output diagnostics. In this paper, we discuss some details regarding these changes and also present simulation results for a number of test cases ranging from LCLS SASE emission to performance of the FERMI@ELETTRA two-stage, harmonic cascade.
* http://www-ssrl.slac.stanford.edu/lcls/technotes/LCLS-TN-04-3.pdf (also LBNL-49625-Rev. 1) |
||
| MOPPH054 | FERMI @ Elettra: A Seeded FEL Facility for EUV and Soft X-Rays | 166 |
|
||
| 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. | ||
| TUPPH055 | A Design for an XUV FEL Driven by the Laser-Plasma Accelerator at the LBNL LOASIS Facility | 455 |
|
||
| We present a design for a compact FEL source of ultra-fast, high-peak flux, soft x-ray pulses employing a high-current, GeV-energy electron beam from the existing laser-plasma accelerator at LBNL's LOASIS facility. The proposed ultra-fast source would be intrinsically temporally synchronized to the drive laser pulse, enabling pump-probe studies in ultra-fast science with pulse lengths of ~10–25 fs. Owing both to the high current (>10 kA) and reasonable charge/pulse (~0.1-0.5 nC) of the laser-plasma-accelerated electron beams, saturated output fluxes are potentially on the order of 1014 photons/pulse. We examine devices based both on SASE and high-harmonic generated input seeds to give improved coherence and reduced undulator length, presenting both analytic scalings and numerical simulation results for expected FEL performance. A successful source would result in a new class of compact laser-driven FELs in which a conventional RF accelerator is replaced by a GeV-class laser-plasma accelerator whose active acceleration region is only several cm in length. | ||
| THAAU01 | Output Bandwidth Effects in Seeded, Harmonic Cascade FELs | 500 |
|
||
| A number of laboratories are studying and/or proposing seeded Harmonic Cascade (HC) FELs as a means both to reach soft x-ray output wavelengths and to provide a degree of longitudinal coherence much greater than that normally possible with SASE devices. While theoretically the output bandwidth of a HC FEL can approach the transform limit given a high quality input seed of reasonable power, there appear to be a number of practical considerations that in many cases can increase the output bandwidth many-fold. In particular, designs that employ dispersive sections following modulator sections in order to increase the amount of coherent harmonic microbunching, can be very sensitive to temporal variations in the electron beam energy, resulting in an output wavelength chirp. Unwanted microbunching induced by the combination of longitudinal space charge instability growth in the linac and CSR in compression sections also can lead to variations in the output radiation phase and amplitude, thus increasing the bandwidth. We give some semi-analytical results for the predicted bandwidth increase for HC configurations and also some detailed numerical simulation results. | ||
|
Slides | |
|
Talk |