TESLA-FEL 2004-02 The Potential for the Development of the X-Ray Free Electron Laser

X-ray photon beam from a SASE FEL undulator is in principle a single user tool, just like an optical laser. Therefore, the operation and amortization cost cannot be easily spread over many simultaneous experiments. To avoid prohibitive cost for each experiment, a new XFEL laboratory scheme is proposed. The wavelength range 0.1-1.6 nm at fixed electron energy of 15 GeV can be covered by operating the SASE FEL with three undulators which have different period and tunable gap. All electrons will be guided into only one electron beamline and dump. Using 0.1% electron (photon) energy shifter in a SASE undulator it is possible to rapidly switch the FEL photon beam from one SASE undulator beamline to the other, providing simultaneous multi-undulator capability. A photon beam distribution system based on movable multilayer X-ray mirrors can provide an efficient way to generate a multi-user facility. Distribution of photons is achieved on the basis of pulse trains and it is possible to partition the photon beam among a few tens independent beamlines thereby obtaining many users working in parallel. The second way to increase the number of simultaneous experiments is based on the working with a series of perfect crystals in transmission (Laue) geometry. The later concept is the basic idea of the Troika beamline at ESRF. In principle, a hundred of photon beamlines with different experiments can be served by a single XFEL source. It is a great advantage that the accelerator and electron beam transport line in the proposed scheme of multi-user facility operate at fixed parameters, thus an ”electron switchyard” is not required. The proposed XFEL scheme is applicable for the Linac Coherent Light Source (LCLS) and European XFEL.