MOOC :: High Gain, Single Pass FELs

Date/Time: 22-Aug-05 :: 15:45—17:30
Chair: T. Tanaka, RIKEN Spring-8, Hyogo

Paper Title Page
MOOC001 Non Linear Pulse Evolution in Seeded and Cascaded FELs 210
 
  • L. Giannessi, S. Spampinati
    ENEA C.R. Frascati, Frascati (Roma)
  • P. Musumeci
    Universita di Roma I La Sapienza, Roma
 
 

The advances in laser technology have made available very short and intense laser pulses which can be used to seed a high gain single pass Free-Electron Laser (FEL) amplifier. With these seed pulses, a regime of the FEL interaction where the radiation evolution is simultaneously dominated by non-linear effects (saturation) and time-dependent effects (slippage) can be explored. This regime is characterized by the propagation of a solitary wave-like pulse where the power of the optical wave grows quadratically with time, its pulse length decreases and the spectral bandwidth increases. We analyze the interplay between the field and particles dynamics of this propagation regime which was studied before and termed superradiance. Furthermore we analyze the properties of the strong higher order harmonics emission from this wave and its behaviour when propagating in a cascade FEL. The superradiant pulse is indeed capable of passing through the stages of a cascade FEL and to regenerate itself at the wavelength of the higher order harmonic. The optical pulse obtained is shorter than a cooperation length and is strongly chirped in frequency, thus allowing further longitudinal compression down to the attosecond time-scale.

 
   
MOOC002 PAL-XFEL Project 216
 
  • I.S. Ko
    PAL, Pohang, Kyungbuk
 
 

Pohang Accelerator Laboratory (PAL) has recently launched a new XFEL project based on SASE technology. This PAL-XFEL will utilize the existing 2.5 GeV injection linac to the storage ring by upgrading its energy up to 3.7 GeV initially and possibly up to 4.5 GeV later on. The wavelength covers up to 0.18 nm when the electron beam energy is 4.5 GeV. In-vacuum undulator will be used to generate FEL lasing. Overall design philosophy and some details will be presented.

 
   
MOOC003 Radiation Spectrum Statistics in a High-Gain Free-Electron Laser at 266 nm 220
 
  • T.V. Shaftan, S. Krinsky, D.F.L. Liu, J.B. Murphy, J. Rose, X.J. Wang, T. Watanabe, L.-H. Yu
    BNL, Upton, Long Island, New York
  • H. Loos
    SLAC, Menlo Park, California
 
 

Funding: The manuscript has been authored by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH1-886 with the U.S. Department of Energy.

We discuss analysis of an experiment with High-Gain Harmonic Generation Free Electron Laser at BNL (DUV FEL). The tunability concept [1] of a seeded FEL with a fixed seed wavelength has been verified experimentally. During the experiment we recorded about 200 radiation spectra corresponding to different energy chirps in the electron beam. We have analyzed this set of spectral data to obtain properties of HGHG radiation. Correlations and trends in the radiation spectrum at 266 nm have been observed and studied.

[1] T. Shaftan and L.H. Yu, Phys. Rev. E 71, 046501 (2005)

 
   
MOOC004 Seeding the FEL of the SCSS Phase 1 Facility with the 13th Laser Harmonic of a Ti: Sa Laser (61.5 nm) Produced in Xe Gas 224
 
  • G. Lambert, M. Bougeard, W. Boutu, P. Breger, M.-E. Couprie, D. Garzella, H. Merdji, P. Monchicourt, P. Salieres
    CEA/DSM/DRECAM/SPAM, Gif-sur-Yvette
  • B. Carre
    CEA/Saclay, Gif-sur-Yvette
  • T. Hara, H. Kitamura, T. Shintake
    RIKEN Spring-8 Harima, Hyogo
 
 

In order to reach very short wavelengths in FEL, and to have a more compact, fully coherent and tunable source, a particular seeding configuration is foreseen to be tested as a demonstration experiment in 2006 into the SCSS phase 1 facility (Spring-8 Compact Sase Source, Japan). The external source is the 13th harmonic (61.5 nm) of a Ti: Sa laser (25 mJ, 10 Hz, 100 fs) generated in 10 Hz pulsed Xe gas cell. The harmonic generation process provides us with a intense (1 μJ) and ultra-short (50 fs) VUV beam. The design of the experiment implantation is discussed, taken into account the performances of the generation process, the focusing of the selected harmonic into the modulator, and the resistance of the optical components. Besides one should consider the vacuum needs, the geometrical problems and the mechanics for the under UHV mirrors translation. One first chamber is dedicated to the harmonic generation. A second one is used for spectral selection and adaptation of the harmonic in the modulator. Finally theoretical estimates of the performances relying on 1D simulations using PERSEO code and 3D simulations using GENESIS code are also given.

 
   
MOOC005 Properties of the Radiation from VUV-FEL at DESY (Femtosecond Mode of Operation) 228
 
  • E. Saldin, E. Schneidmiller, M.V. Yurkov
    DESY, Hamburg
 
 

Present bunch compression scheme at the VUV FEL is essentially nonlinear and naturally results in a formation of a short high-current leading peak (spike) in the density distribution that produces FEL radiation. The main feature of the considered mode of operation is the production of short (15-50 fs FWHM) radiation pulses with GW-level peak power that are attractive for many users. In this paper we present main parameters of the SASE FEL radiation: temporal and spectral characteristics, intensity distributions, etc. We also analyze statistical properties of the radiation from a SASE FEL driven by short electron bunches. In the linear regime the radiation from a SASE FEL is a Gaussian random process. When approaching saturation point, statistical properties of the radiation change drastically on a scale of one field gain length. Particular attention is devoted to the analysis of fluctuations of total energy in the radiation pulse and after a narrow-band monochromator. It is shown that fluctuations at saturation are significantly suppressed when electron pulse length becomes comparable with cooperation length.