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X-ray Free Electron lasers Zhirong Huang Slide 2 Lecture Outline XFEL basics XFEL basics XFEL projects and R&D areas XFEL projects and R&D areas Questions and Answers Questions and Answers Slide 3 Bright light sources from relativistic electrons Electrons emit with random phase radiation intensity N ( is Lorentz factor, N is number of electrons ~10 9 ) Synchrotron radiationUndulator radiation Slide 4 Produced by resonant interaction of a relativistic electron beam with EM radiation in an undulator Free Electron Laser (FEL) electron beam photon beam e beam dump undulator 1 Radiation intensity N 2 Tunable, Powerful, Coherent radiation sources Slide 5 Three FEL modes Slide 6 Light Source Brightness (Brilliance) 10 orders of magnitude! Slide 7 u forward direction radiation (and harmonics) undulator parameter K = 0.94 B[Tesla] u [cm] undulator parameter K = 0.94 B[Tesla] u [cm] Can energy be exchanged between electrons and co- propagating radiation pulse? 1 LCLS undulator K = 3.5, u = 3 cm, e-beam energy from 3 GeV to 15 GeV to cover 1 = 30 to 1.2 Undulator Radiation Slide 8 z x Due to sustained interaction, some electrons lose energy, while others gain energy modulation at 1 e losing energy slow down, and e gaining energy catch up density modulation at 1 (microbunching) Microbunched beam radiates coherently at 1, enhancing the process exponential growth of radiation power u 1x-ray Electrons slip behind EM wave by 1 per undulator period ( u ) ++ ++ ++ ++ ++ ++ K/K/K/K/ v x E x > 0 ++ Resonant Interaction of Field with Electrons E t E t v x E x > 0 P. Emma Slide 9 FEL Micro-Bunching Along Undulator S. Reiche log (radiation power) distance electron beam photon beam e beam dump undulator Slide 10 Shot noise originates from discrete nature of electrons What is SASE? ..... zz SASE electron arrival time t is random spontaneous emission amplified by FEL interaction quasi-coherent x-rays Slide 11 SASE FEL Electron Beam Requirements < 1 m at 1 , 15 GeV