| Paper |
Title |
Page |
| MOPPH054 |
Spectral Characteristics of the Seeded FEL Using Higher Harmonic Generation in a Gas at the SCSS Test Accelerator
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106 |
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- T. Tanikawa
Sokendai, Okazaki, Aichi
- B. Carré, D. Garzella, M. Labat
CEA, Gif-sur-Yvette
- M.-E. Couprie
SOLEIL, Gif-sur-Yvette
- T. Hara, T. Ishikawa, H. Kitamura, T. Shintake, T. Tanaka, M. Yabashi
RIKEN/SPring-8, Hyogo
- M. Katoh
UVSOR, Okazaki
- G. Lambert
LOA, Palaiseau
- K. Tahara, Y. T. Tanaka
RIKEN Spring-8 Harima, Hyogo
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Seeding a FEL with high order harmonic generation (HHG) from a Xe gas cell at the SCSS test accelerator was achieved at a wavelength of 160 nm (the 5th harmonic of a Ti: Sa laser) in December 2006. After the improvement of the accelerator performance in 2007, we performed detailed studies of the spectral characteristics of the seeded FEL. Compared to the spiky spectrum of SASE, the seeded FEL can produce a quasi-Gaussian spectrum with a single peak. In addition, the lasing wavelength is fixed at the wavelength of the seed, even if the undulator K-parameter is shifted in a certain range. Therefore, the spectral stability becomes much better than SASE against the fluctuation of undulator fields or beam energy. In the recent experiments, we observed that the bandwidth of the amplified seed became narrower than that of the original seed light itself. It seems to be stretched the longitudinal coherent length in the FEL interaction. In the presentation, we will report the spectral characteristics of the seeded FEL.
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| MOPPH066 |
The ARC-EN-CIEL Fourth Generation Light Source Proposal
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131 |
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- M.-E. Couprie, C. Benabderrahmane, O. V. Chubar, J. Denard, P. Dumas, J.-M. Filhol, M. Idir, M. Labat, P. Lebasque, A. Lestrade, M. Louvet, P. Marchand, O. Marcouillé, P. Mercere, P. Morin, L. S. Nadolski, L. Nahon
SOLEIL, Gif-sur-Yvette
- C. Bruni
LAL, Orsay
- E. Collet
University of Rennes, Rennes
- D. Garzella
CEA, Gif-sur-Yvette
- L. Giannessi
ENEA C. R. Frascati, Frascati (Roma)
- G. Lambert, P. Zeitoun
LOA, Palaiseau
- J. Luning
CCPMR, Paris
- M. Meyer
LIXAM, Orsay
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The ARC-EN-CIEL project proposes a suit of novel light sources for the scientific community. Three FEL (LEL1, LEL2 and LEL4) sources rely on High Gain Harmonic Generation radiation and their Non Linear Harmonics seeded with the High Order Harmonics generated in gas. LEL1 will cover the 200-1.5 nm spectral range with 100-30 fs FWHM pulses, adjustable in polarisation, at a few kHz. LEL2 will provide 10-0.6 nm radiation with planar polarisation, with 100-30 fs pulses at a few kHz repetition rate. LEL4 will cover the 2-0.2 nm range, with 50-30 fs pulses at 1 kHz. LEL3 is a FEL oscillator in the 40-8 nm range with a repetition rate of 4.5 MHz. These FEL sources will reach MW to GW of peak power. In addition, undulator radiation will provide 200 fs pulses with energies up to 20 keV. FEL calculations are presented. . The accelerator is based on superconducting technology to enable a high repetition rate. ARC-EN-CIEL is well adapted for studies in various scientific domains using coherent imaging, linear spectroscopy, pump-probe experiments, non-linear and high intensities studies. The use of plasma acceleration in the project is under investigation.
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| MOPPH072 |
Operation of the UVSOR-II FEL in Helical Mode
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143 |
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- M. Labat
CEA, Gif-sur-Yvette
- M.-E. Couprie
SOLEIL, Gif-sur-Yvette
- M. Hosaka
Nagoya University, Nagoya
- M. Katoh, M. Shimada
UVSOR, Okazaki
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Seeded Free Electron Lasers (FELs) - an external laser source is injected inside the undulator to perform energy modulation of the electron beam - deliver intense, short duration, short wavelength light pulses with a high temporal coherence degree. Since the polarization of the radiation depends on the undulator magnetic field, the FELs operated with adjustable undulators are unique candidates for providing flexible polarized light of high quality, required for probing symmetry properties of matter. Experiments have been performed on the UVSOR-II storage ring FEL in the seeded Coherent Harmonic Generation (CHG) scheme operated with helical undulators. The electron beam stored at 500 MeV is seeded using a 800 nm Ti:Sa laser, allowing radiation at 400 nm (second harmonic). A quarter-wavelength plate allows the tuning of the polarization of the seeded laser from linear to elliptic or circular. We show that the FEL radiation intensity can be significantly improved via the seed polarization matching. Other parameters of optimization are also presented, such as the focussing mode. The experimental results are analysed using a simple 1D analytical model and the 3D numerical code GENESIS.
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| TUBAU01 |
VUV Seeded FEL Experiment at the SCSS Test Accelerator
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207 |
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- T. Hara, T. Ishikawa, H. Kitamura, T. Ohshima, T. Shintake, T. Tanaka, M. Yabashi
RIKEN/SPring-8, Hyogo
- B. Carré, D. Garzella
CEA, Gif-sur-Yvette
- M.-E. Couprie, M. Labat
SOLEIL, Gif-sur-Yvette
- G. Lambert
LOA, Palaiseau
- K. Tahara, Y. T. Tanaka
RIKEN Spring-8 Harima, Hyogo
- T. Tanikawa
Sokendai, Okazaki, Aichi
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Short wavelength seeded FEL has been demonstrated at the SCSS test accelerator using high order harmonics generated in gas of a Ti:Sa laser as an external seed source. After the improvement of the accelerator stability and undulator magnetic errors in 2007, the FEL gain was drastically increased and detailed measurements have been carried out on the spectral characteristics and seeding power level of the seeded FEL. Although the wavelength of the seed is 160 nm for the moment, we have succeeded to observe up to 7th nonlinear harmonics (23 nm) of the 160 nm FEL fundamental including both odd and even harmonics. It leads to the development of a short wavelength seeded FEL. Currently we are working on the modification of the seeding system in order to reach a 50-60 nm range using high order harmonics in the plateau region. By combining a short wavelength seed with nonlinear harmonics, a seeded FEL below 10 nm becomes feasible. In the conference, we will present the recent results of the experiments together with the technical issues of the seeded FEL, such as temporal jitter between laser pulses and electron bunches.
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| TUPPH015 |
Construction of Short Period APPLE II Type Undulators at SOLEIL
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265 |
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- F. Briquez, C. Benabderrahmane, O. V. Chubar, M.-E. Couprie, T. K. El Ajjouri, C. A. Kitegi, F. Marteau, A. Mary, K. Tavakoli, J. Vétéran
SOLEIL, Gif-sur-Yvette
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We present here the conception, construction and magnetic measurements of APPLE II type undulators of period 44 mm and 36 mm at SOLEIL. Such short period undulators are difficult to design and construct because of the little dimensions of the magnets, leading to small support structures which are more easily bent by the magnetic forces. The design of the support structures consists in individual aluminium holders grouped in assemblies of three or five magnets called modules and fixed on the girders using dovetails. Special extremity modules are designed to reduce field integrals of the undulator. The magnets are independently measured using Helmoltz coils and sorted in modules. Then the modules are measured using Hall probes and bodyless coil, and sorted to assemble the undulator. After assembling, a shimming is done to correct phase errors and field integrals, and a final correction of the integrals is made by little extremity magnets called "Magic Fingers". For each step of sorting, we use the home-made IDBuilder software, based on genetic algorithms. Short period undulators are of interest for the ARC-EN-CIEL project, which considers APPLE-II with a 30 mm period.
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| TUPPH048 |
Recent Results of the SPARC Project
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359 |
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- M. Ferrario, D. Alesini, M. Bellaveglia, R. Boni, M. Boscolo, M. Castellano, E. Chiadroni, A. Clozza, L. Cultrera, G. Di Pirro, A. Drago, A. Esposito, L. Ficcadenti, D. Filippetto, V. Fusco, A. Gallo, G. Gatti, A. Ghigo, A. Marcelli, B. Marchetti, M. Migliorati, A. Mostacci, E. Pace, L. Palumbo, L. Pellegrino, R. Ricci, U. Rotundo, C. Sanelli, F. Sgamma, B. Spataro, F. Tazzioli, S. Tomassini, C. Vaccarezza, M. Vescovi, C. Vicario
INFN/LNF, Frascati (Roma)
- A. Bacci, I. Boscolo, F. Broggi, F. Castelli, S. Cialdi, C. De Martinis, D. Giove, C. Maroli, V. Petrillo, A. R. Rossi, L. Serafini
Istituto Nazionale di Fisica Nucleare, Milano
- M. Bougeard, B. Carré, D. Garzella, M. Labat, G. Lambert, H. Merdji, P. Salieres, O. Tchebakoff
CEA, Gif-sur-Yvette
- L. Catani
INFN-Roma II, Roma
- A. Cianchi
Università di Roma II Tor Vergata, Roma
- F. Ciocci, G. Dattoli, M. Del Franco, A. Dipace, A. Doria, G. P. Gallerano, L. Giannessi, E. Giovenale, G. L. Orlandi, S. Pagnutti, A. Petralia, M. Quattromini, C. Ronsivalle, E. Sabia, I. P. Spassovsky, V. Surrenti
ENEA C. R. Frascati, Frascati (Roma)
- M.-E. Couprie
SOLEIL, Gif-sur-Yvette
- A. Marinelli, J. B. Rosenzweig
UCLA, Los Angeles, California
- M. Mattioli, M. Petrarca, M. Serluca
INFN-Roma, Roma
- J. Rossbach
Uni HH, Hamburg
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The SPARC project foresees the realization of a high brightness photo-injector to produce a 150-200 MeV electron beam to drive 500 nm FEL experiments in various configurations. The SPARC photoinjector is also the test facility for the recently approved VUV FEL project named SPARX. The second stage of the commissioning, that is currently underway, foresees a detailed analysis of the beam matching with the linac in order to confirm the theoretically prediction of emittance compensation based on the “invariant envelope” matching , the demonstration of the “velocity bunching” technique in the linac and the characterisation of the spontaneous emission radiation in the SPARC undulators. In this paper we report the experimental results obtained so far.
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| TUPPH080 |
FEL Emissions at 160 nm in Seeded Configuration on the SCSS Test Accelerator
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429 |
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- G. Lambert
LOA, Palaiseau
- M. Bougeard, B. Carré, D. Garzella, O. B. Gobert, M. Labat, H. Merdji, P. Salieres
CEA, Gif-sur-Yvette
- O. V. Chubar, M.-E. Couprie
SOLEIL, Gif-sur-Yvette
- T. Hara, H. Kitamura, T. Shintake, M. Yabashi
RIKEN/SPring-8, Hyogo
- T. Ishikawa, K. Tahara, Y. T. Tanaka
RIKEN Spring-8 Harima, Hyogo
- T. Tanikawa
UVSOR, Okazaki
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Recently it has been proved that seeding a Free-Electron Laser with Harmonics Generated in gas can drastically improve the properties of the light emission and in particular the temporal coherence, which is quite limited in the Self-Amplified Spontaneous Emission configuration. Here, the impact of the seed level on the FEL emission has been characterized at 160 nm on the SCSS Test Accelerator. Actually, at extremely low level of HHG injection (0.5 pJ, 10 W), i.e. approximately ten times the effective noise power of the SASE emission, the FEL emission starts to be amplified and the number of spikes decrease. Then, the FEL energy per pulse begins clearly proportional to the HHG energy per pulse. More specifically for a seed power (<175 W) 230 times larger than the effective SASE noise power, the FEL spectrum exhibits a stable quasi Gaussian shape. As it is theoretically feasible to generate XUV harmonics which can be dominating with a similar factor, one can imagine High Gain Harmonic Generation configurations with only two or three stages for reaching wavelengths of a few nanometers.
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