WEPA  —  Poster: Short Pulse Length FELs   (25-Aug-10   13:30—15:00)

Paper Title Page
WEPA01 Short Pulse Radiation from an Energy-Chirped Electron Bunch in a Soft-X-Ray FEL 358
 
  • I.P.S. Martin
    Diamond, Oxfordshire
  • R. Bartolini, I.P.S. Martin
    JAI, Oxford
 
 

The production of short pulse radiation of 1fs or below would open up many new areas of research. Saldin et al recently proposed a scheme to generate such pulses, in which a laser pulse consisting of only a few optical cycles is used to give a short energy chirp to the electron bunch and uses a tapered undulator to compensate the chirped region. In this paper we study the application of this scheme to a soft x-ray free electron laser, including the results of fully start to end simulations and an assessment of the sensitivity to jitter.

 
WEPA02 SASE FEL at SDUV-FEL 362
 
  • D.G. Li, J.H. Chen, H.X. Deng, C. Feng, Q. Gu, T. Lan, G.Q. Lin, B. Liu, D. Wang, X. Wang, M. Zhang, Z.T. Zhao
    SINAP, Shanghai
 
 

A SASE experiment has been done at SDUV-FEL(SINAP), the spontaneous radiation and exponential growth regime are observated. The results are compared with the SASE theory.

 
WEPA04 Femtosecond Electron Bunch Generation Using Photocathode RF Gun 366
 
  • K. Kan, T. Kondoh, T. Kozawa, K. Norizawa, A. Ogata, J. Yang, Y. Yoshida
    ISIR, Osaka
 
 

Femtosecond electron beam, which is essential for pump-probe measurement, was generated with a 1.6-cell S-band photocathode rf gun. The rf gun was driven by femtosecond UV laser pulse (266 nm), which was generated with third-harmonic-generation (THG) of Ti:Sapphire femtosecond laser (800 nm). The longitudinal and transverse dynamics of the electron bunch generated by the UV laser was investigated. The bunch length was measured with the dependence of energy spread on acceleration phase in a linac, which was set at the downstream of the rf gun. Transverse emittance at the linac exit was also measured with Q-scan method.

 
WEPA07 Variable Gap Undulator for 1.5-48 keV Free Electron Laser at LINAC Coherent Light Source 370
 
  • C. Pellegrini
    UCLA, Los Angeles, California
  • J. Wu
    SLAC, Menlo Park, California
 
 

Success in commissioning the world's first x-ray (0.15-1.5 nm) free electron laser (FEL) - the LINAC Coherent Light Source (LCLS) - at SLAC National Accelerator Laboratory opens the gate for new science. Further improving the FEL spectrum bandwidth, shortening the FEL pulse temporal duration, and generating even higher energy x-ray photons are urged by various potential users. In this paper, we study the possibility of generating femtosecond duration X-ray pulses with a variable photon energy from 1.5 to 48 keV, using an electron beam with the same characteristics of the LCLS beam, and a planar undulator with additional focusing. We assume that the beam energy can be changed, and the undulator has a variable gap, allowing the undulator parameter to be changed from zero to a maximum value. It is assumed to be operated in an ultra-low charge and ultra-short pulse regime.

 
WEPA09 A Compact Electro Optical Bunch Length Monitoring System - First Results at PSI 374
 
  • F. Müller, P. Peier, V. Schlott
    PSI, Villigen
  • B. Steffen
    DESY, Hamburg
 
 

Electro Optical (EO) sampling is a promising non-destructive method for measuring ultra short (sub picosecond) electron bunches. A prototype of a compact EO bunch length monitor system for the future SwissFEL facility was designed and built at PSI. Its core components are an optical setup including the electro optically active crystal and an Ytterbium fiber laser system which emits broadband pulses at 1050nm. The new monitoring system is described in detail and first experimental results from the SLS injector are presented.

 
WEPA10 Electro Optical Measurement of Coherent Synchrotron Radiation for Picosecond Electron Bunches With Few pC 378
 
  • B. Steffen
    DESY, Hamburg
  • F. Müller, P. Peier, V. Schlott
    PSI, Villigen
 
 

Electro Optical (EO) sampling is a promising non-destructive method for measuring ultra short (sub-ps) electron bunches. The FEMTO slicing experiment at the Swiss Light Source modulates about 3 pC of the 5 nC electron bunch longitudinally. The coherent synchrotron radiation (CSR) emitted by this substructure was measured in a single shot EO technique in gallium phosphide (GaP) using pulses from an Yb fiber laser. The arrival time jitter and the broadening of this ps long structure over several turns of the synchrotron could be measured with sub-ps resolution.

 
WEPA11 The MAX IV Injector as a Soft X-Ray FEL Driver 382
 
  • S. Werin, N. Čutić, M. Eriksson, F. Lindau, S. Thorin
    MAX-lab, Lund
 
 

The MAX IV injector is funded and under construction. It is designed to drive a Short Pulse Facility generating spontaneous incoherent photon pulses in the keV range with pulse lengths below 100 fs in the first phase of the project. This source will with minor modifications be able to drive a Free Electron Laser down into the soft X-ray region and with an extended energy a full X-ray FEL at 1-2 Å. The key feature of the system is the availability of a 3-3.5 GeV linac, a low emittance photo cathode RF-gun and two bunch compressors including sextupoles for linearization. By extracting pulses of 0.1-0.2 nC charge, normalized emittances below 1 mm mRad and peak currents above 3 kA can be achieved. Such pulses are very well suited for a FEL facility. We describe the MAX IV injector system and discuss the options and perspectives for an X-ray FEL at the MAX IV facility.

 
WEPA14 Ultrafast X-Ray Pulse Measurement Method 386
 
  • G. Geloni
    European XFEL GmbH, Hamburg
  • V. Kocharyan, E. Saldin
    DESY, Hamburg
 
 

In this paper we describe a measurement technique capable of resolving femtosecond X-ray pulses from XFEL facilities. Since these ultrashort pulses are themselves the shortest event available, our measurement strategy is to let the X-ray pulse sample itself. Our method relies on the application of a "fresh" bunch technique, which allows for the production of a seeded X-ray pulse with a variable delay between seed and electron bunch. The shot-to-shot averaged energy per pulse is recorded. It turns out that one actually measures the autocorrelation function of the X-ray pulse, which is related in a simple way to the actual pulse width. For implementation of the proposed technique, it is sufficient to substitute a single undulator segment with a short magnetic chicane. The focusing system of the undulator remains untouched, and the installation does not perturb the baseline mode of operation. We present a feasibility study and we make exemplifications with typical parameters of an X-ray FEL.