| Paper | Title | Page |
|---|---|---|
| TUP002 | Characterization of Partially Coherent Ultrashort FEL Pulses | 346 |
|
||
| Temporal metrology is a major need for free-electron lasers. However, the lack of longitudinal coherence, that is shot-to-shot fluctuations, of these sources has prevented so far the full amplitude and phase temporal characterization of FEL pulses. To sort out this issue, we propose a solution inspired from attosecond metrology, where XUV pulse measurement techniques already exist, and from coherent diffraction imaging, where numerical solutions have been developed for processing partially coherent diffraction patterns. The experimental protocole implies the measurement of photoelectron spectra obtained through XUV-laser photoionisation. The spectra are then processed with an algorithm in order to retrieve the partially coherent FEL pulse. When applied to SASE FELs, the technique gives access to the full statistics of the emitted pulses. With seeded-FELs, the pulse shape becomes stable from shot-to-shot, but an XUV-laser time jitter remains. In that case, the technique enables the joint measurement of the FEL pulse shape (in amplitude and phase) and of the laser/FEL jitter envelope. The concept has been validated with numerical simulations in the context of the LUNEX5 FEL project. | ||
| TUP086 | Experiment Preparation Towards a Demonstration of Laser Plasma Based Free Electron Laser Amplification | 569 |
|
||
| One direction towards compact Free Electron Laser is to replace the conventional linac by a laser plasma driven beam, provided proper electron beam manipulation to handle the value of the energy spread and of the divergence. Applying seeding techniques also enables to reduce the required undulator length. Rapidly developing Laser Wakefield Accelerators (LWFA) are already able to generate synchrotron radiation. With the presently achieved electron divergence and energy spread an adequate beam manipulation through the transport to the undulator is needed for FEL amplification. A test experiment for the demonstration of FEL amplification with a LWFA is under preparation in the frame of the COXINEL ERC contract in the more general context of LUNEX5. Electron beam transport follows different steps with strong focusing thanks to variable strength permanent magnet quadrupoles, demixing chicane with conventional dipoles, and a second set of quadrupoles for further focusing in the undulator. Progress on the equipment preparation and expected performance are described. | ||
THP001 |
Beam Manipulation for Plasma Accelerator Based Free Electron Lasers | |
|
||
| Longitudinal decompression of electron beams delivered by state-of-the-art Laser WakeField Accelerators (LWFA) eases the free-electron laser process. We propose here an additional second order transverse beam manipulation, only based on quadrupoles, turning the very large inherent transverse chromatic emittances of LWFA beam into direct FEL gain advantage. This complete transfer line scheme is presently under construction for the projects COXINEL recently funded by an ERC advanced grant. Numerical simulations showing that this beam manipulation can further enhance by orders of magnitude the peak power of the radiation are presented. | ||
THP078 |
A High Repetition Rate, Single-Shot Recording Scheme for Short Pulses | |
|
||
| We demonstrate high repetition rate (up to 88 MHz) single shot recordings of pulses shapes, using a novel opto-electronic strategy. The technique is based on the classical spectral encoding technique, but at a much higher repetition rate than with the state-of-art strategy (which is limited by camera speed). In the present demonstration, the signals are coherent THz pulses emitted at SOLEIL, and the resolution is in the ps range. However the technique is not specific to THz pulses and can be potentially adapted to other wavelengths and situations, provided it is possible to imprint the ultrafast signal on chirped laser pulses (through electro-optic sampling, frequency mixing, transient reflectivity, etc.). | ||
THP079 |
Observation of Laser-Sliced Electron Bunch using a YBCO Detector at UVSOR-III | |
|
||
|
When the current of a storage ring is near the microbunching instability threshold, a strong burst of CSR instability may be seeded by an external laser pulse*. Here we present real time recordings of the coherent synchrotron radation (CSR) pulse shapes emitted by sliced electron bunch using a new technology based on YBCO thin film detector combined with the state-of-the-art oscilloscope. This allows to make measurements in real time of the sliced electron bunch dynamics over several turns. These experimental observations open a new way to make severe comparisons with existing and future models of the microbunching instability. Tests of a Vlasov-Fokker-Planck model are presented.
* Byrd et al. Phys. Rev. Lett. 97, 074802 (2006) |
||
| TUP087 | The Status of LUNEX5 Project | 574 |
|
||
| LUNEX5 (free electron Laser Using a New accelerator for the Exploitation of X-ray radiation of 5th generation) aims at investigating the production of short, intense, coherent Free Electron Laser (FEL) pulses in the 40-4 nm spectral range. It comprises a 400 MeV superconducting Linear Accelerator for high repetition rate operation (10 kHz), multi-FEL lines and adapted for studies of advanced FEL schemes, a 0.4 - 1 GeV Laser Wake Field Accelerator (LWFA) for its qualification by a FEL application, a single undulator line enabling seeding with High order Harmonic in Gas and echo configurations and pilot user applications. Concerning the superconducting linac, the electron beam dynamics has been modified from a scheme using a third harmonic linearizer and a compression chicane to dog-leg coupled to sextupoles. Besides, the choice of the gun is under revision for fulfilling to 10 kHz repetition rate. Following transport theoretical studies of longitudinal and transverse manipulation of a LWFA electron beam enabling to provide theoretical amplification, a test experiment is under preparation in collaboration with the Laboratoire d’Optique Appliquée towards an experimental demonstration. | ||