• G. Dattoli, A. Renieri
  ENEA C.R. Frascati, Frascati (Roma)

The existing soft and hard X-Ray FEL Projects are discussed, along with the underlying design and technological strategies. We consider two main categories: large facilities, which will involve the joint efforts of big laboratories and will take benefit from the heritage of high energy Physics facilities and smaller devices, which are aimed at exploiting high quality accelerators with modest e-beam energy to reach shorter wavelengths with alternative schemes. We will discuss advantages and drawbacks of the different conceptions and make an outlook to the future developments, with particular attention to combinations of different solutions like exotic undulators, seeding and so on, aimed not only at improving X-ray beam qualities but also at reducing device complexity and cost.

• D.A. Reis
  Michigan University, Ann Arbor, Michigan

We present recent results from the Sub-picosecond Pulse Source (SPPS) which produces hard x-ray pulses as short as 80fs in duration from the compressed ultrarelativistic electron beam at SLAC. Using these pulses, we have performed single-shot experiments on the dynamics of laser-induced ultrafast disordering in semiconductors with unprecedented temporal resolution. However, for repetitive pump-probe experiments, timing jitter between the laser pump and the x-ray probe can lead to severely reduced temporal resolution. To overcome this problem, we measure the relative timing on a shot-by-shot base using spatially resolved electro-optic sampling of the electron beam.

• R.M. Bionta
  LLNL, Livermore, California

Funding: This work was performed under the auspices of the U.S. Department of Energy by the University of California, Lawrence Livermore National Laboratory under contract Number W-7405-Eng-48 and by Stanford University, Stanford Linear Accelerator Center under contract Number DE-AC03-76SF00515 for the LCLS project.

The Linac Coherent Light Source (LCLS) will generate X-FEL radiation with photon energies tunable from 826 eV to 8261 eV. It is expected that elements of the Linac and Undulator systems will require careful tuning in order to achieve lasing at these wavelengths. The tuning will be guided by measurements of both the electron and photon beam characteristics. The primary characteristics of the photon beam that can be measured are the total pulse energy, its spatial shape, and spectra. During the initial commissioning phase, these measurements will be performed on the spontaneous radiation emitted by one or more undulators as they are added to the LCLS. The next phase of commissioning requires detecting and measuring faint (unsaturated) FEL radiation for the purposes of tuning the Linac and undulator to achieve saturation. During the last phases of commissioning these measurements will have to be performed on the saturated FEL beam. The photon measurements are complicated by the large dynamic range required, the short (x-ray) wavelengths, the range of x-ray wavelengths, the small beam divergence, and the need to worry about the survivability of materials placed in the beam. We will discuss plans for the instrumentation in the LCLS’s Front-End Enclosure where these measurements will be carried out.