Concepts for Laser-Plasma Driven FELs Andreas R. Maier CFEL, UHH, LAOLA. [email protected] lux.cfel.de CFEL SCIENCE LAOLA. is a collaboration of LAOLA Collaboration LAOLA. LAOLA@PITZ LAOLA@FLASH LAOLA@REGAE self-modulation contact: Frank Stephan, PITZ beam-driven (now called: FLASHforward) contact: Jens Osterhoff, DESY laser-driven contact: Andreas Maier, CFEL/UHH CFEL SCIENCE external injection triggered injection backup slides my group 2 Andreas R. Maier | [email protected] | lux.cfel.de | LA3NET Workshop | April 30, 2014 | Page 00 LUX Junior Research group ‣ „laser-plasma driven light source“ ‣ 2 PostDocs, 4 PhDs, 3 Master students ‣ lux.cfel.de operate 200 TW ANGUS laser system beamline for laser-plasma driven undulator radiation research on table-top FELs CFEL SCIENCE 3 Andreas R. Maier | [email protected] | lux.cfel.de | LA3NET Workshop | April 30, 2014 | Page 00 Outline 1) FELs in a nutshell 2) Plasma-based FELs Free-Electron Lasers ... in a nutshell Free-Electron Lasers electron beam electron source CFEL SCIENCE beam optics x-ray beam undulator 6 Andreas R. Maier | [email protected] | lux.cfel.de | LA3NET Workshop | April 30, 2014 | Page 00 Free-Electron Lasers electron beam electron source beam optics x-ray beam undulator why is it so cool? 13 O(10 ) ‣ high number of photons - order of ‣ coherent (sort of...) ‣ wavelengths from soft to hard x-rays ‣ fs-scale pulse lengths CFEL SCIENCE 7 Andreas R. Maier | [email protected] | lux.cfel.de | LA3NET Workshop | April 30, 2014 | Page 00 Free-Electron Lasers electron beam electron source beam optics x-ray beam undulator natural time and length scale of matter CFEL SCIENCE 8 Andreas R. Maier | [email protected] | lux.cfel.de | LA3NET Workshop | April 30, 2014 | Page 00 Undulator Radiation u K/ uB y x z ‣ co-moving frame: electrons oscillate, emit dipole radiation, wavelength proportional to Lorentz-contracted undulator period ‣ doppler shift CFEL SCIENCE / ! u / u 2 9 Andreas R. Maier | [email protected] | lux.cfel.de | LA3NET Workshop | April 30, 2014 | Page 00 Undulator Radiation K/ u uB y x z strength of „electron shaker“ period of „electron shaker“ (could also be a laser) (could also be a laser) = 2 u (1 2 2 + K /2) electron beam energy CFEL SCIENCE (powerful tuneability) 10 Andreas R. Maier | [email protected] | lux.cfel.de | LA3NET Workshop | April 30, 2014 | Page 00 What happens next? Calvin & Hobbes by Bill Watterson self-interaction: electrons move in their self-emitted radiation field causes energy modulation dW / E · v = Ex v x dt CFEL SCIENCE 11 Andreas R. Maier | [email protected] | lux.cfel.de | LA3NET Workshop | April 30, 2014 | Page 00 What happens next? Calvin & Hobbes by Bill Watterson self-interaction: electrons move in their self-emitted radiation field causes energy modulation undulator is a dispersive device electrons fall back / advance in phase CFEL SCIENCE transverse coordinate dW / E · v = Ex v x dt γ < γr γr −λ γ > γr 0 −λ/2 longitudinal bunch coordinate 12 Andreas R. Maier | [email protected] | lux.cfel.de | LA3NET Workshop | April 30, 2014 | Page 00 What happens next? Calvin & Hobbes by Bill Watterson self-interaction: electrons move in their self-emitted radiation field causes energy modulation η × 10−3 4 dW / E · v = Ex v x dt 2 0 −2 4 3 2 1 −2λ −λ 0 λ longitudinal bunch coordinate electrons gather locally wavefronts add coherently undulator is a dispersive device electrons fall back / advance in phase CFEL SCIENCE transverse coordinate n/n0 −4 γ < γr γr −λ γ > γr 0 −λ/2 longitudinal bunch coordinate 13 Andreas R. Maier | [email protected] | lux.cfel.de | LA3NET Workshop | April 30, 2014 | Page 00 Self-amplifying process... 108 gain: P/P0 106 saturation 104 exponential gain lethargy regime 102 100 0 5 10 15 undulator length: z/Lg 20 25 electron beam electron source CFEL SCIENCE beam optics x-ray beam undulator 14 Andreas R. Maier | [email protected] | lux.cfel.de | LA3NET Workshop | April 30, 2014 | Page 00 FEL requires high electron beam quality electron / light interaction high current generates strong Efield to start with η × 10−3 4 2 0 −2 4 3 2 1 −2λ −λ 0 transverse coordinate n/n0 −4 λ longitudinal bunch coordinate electrons gather locally dispersion CFEL SCIENCE γ < γr γr −λ γ > γr 0 −λ/2 longitudinal bunch coordinate 15 Andreas R. Maier | [email protected] | lux.cfel.de | LA3NET Workshop | April 30, 2014 | Page 00 FEL requires high electron beam quality electron / light interaction high current generates strong Efield to start with η × 10−3 4 2 0 −2 4 3 2 1 −2λ −λ 0 longitudinal bunch coordinate electrons gather locally CFEL SCIENCE λ low energy spread otherwise dispersion has no net effect dispersion transverse coordinate n/n0 −4 γ < γr γr −λ γ > γr 0 −λ/2 longitudinal bunch coordinate 16 Andreas R. Maier | [email protected] | lux.cfel.de | LA3NET Workshop | April 30, 2014 | Page 00 FEL requires high electron beam quality growth rate - competition of microbunching vs. diffraction high current generates strong Efield to start with 4 η × 10−3 electron / light interaction 2 0 −2 4 3 2 1 −2λ −λ 0 longitudinal bunch coordinate electrons gather locally CFEL SCIENCE λ low energy spread otherwise dispersion has no net effect dispersion transverse coordinate n/n0 −4 γ < γr γr −λ γ > γr 0 −λ/2 longitudinal bunch coordinate 17 Andreas R. Maier | [email protected] | lux.cfel.de | LA3NET Workshop | April 30, 2014 | Page 00 RF-driven FELs - a success story electron beam electron source beam optics x-ray beam undulator the electron source determines the FEL design with different source (plasma) expect a different FEL design CFEL SCIENCE 18 Andreas R. Maier | [email protected] | lux.cfel.de | LA3NET Workshop | April 30, 2014 | Page 00 RF-driven FELs - a success story electron beam electron source beam optics RF electron gun determines everything: ‣ diffraction (of radiation) ‣ current ‣ km accelerator for GeV electrons, i.e. hard xrays CFEL SCIENCE x-ray beam undulator 100 m long undulator, determined by ‣ current, ‣ wakefields (backup slides), ‣ radiation diffraction 19 Andreas R. Maier | [email protected] | lux.cfel.de | LA3NET Workshop | April 30, 2014 | Page 00 RF-driven FELs - a success story electron source beam optics CFEL SCIENCE a m s undulator a pl RF electron gun determines everything: ‣ diffraction (of radiation) ‣ current ‣ km accelerator for GeV electrons, i.e. hard xrays L E F n e v i r -d potentially much higher m-scale for GeV electron beam x-ray beam 100 m long undulator, determined by ‣ current, ‣ wakefields (backup slides), ‣ radiation diffraction different 20 Andreas R. Maier | [email protected] | lux.cfel.de | LA3NET Workshop | April 30, 2014 | Page 00 RF-driven FELs - a success story electron source beam optics L E F n e v i r -d pl a m s undulator a electron beam x-ray beam one should really expect a completely different FEL design CFEL SCIENCE 21 Andreas R. Maier | [email protected] | lux.cfel.de | LA3NET Workshop | April 30, 2014 | Page 00 first chance to stop the talk... Calvin & Hobbes by Bill Watterson What about energy spread? ‣ obvious solution - reduce energy spread ‣ pragmatic solution - live with it! transverse coordinate ‣ dispersion is a local effect ‣ low energy spread is only required locally low energy spread otherwise dispersion has no net effect γ < γr γr −λ γ > γr 0 −λ/2 longitudinal bunch coordinate dispersion CFEL SCIENCE 23 Andreas R. Maier | [email protected] | lux.cfel.de | LA3NET Workshop | April 30, 2014 | Page 00 Paradigm break ‣ very active research ‣ new direction: be pragmatic ‣ use currently available beams and many more on FEL’13: Couprie et al., Schroeder et al., Campbell et al., ... CFEL SCIENCE 24 Andreas R. Maier | [email protected] | lux.cfel.de | LA3NET Workshop | April 30, 2014 | Page 00 Decompression chicane electron beam undulator beam optics 620 620 600 600 γ γ electron source x-ray beam 580 580 −5 0 ζ (µm) 5 −5 0 ζ (µm) 5 A. R. Maier et al., PRX 2, 031019 (2012) CFEL SCIENCE 25 Andreas R. Maier | [email protected] | lux.cfel.de | LA3NET Workshop | April 30, 2014 | Page 00 Calvin & Hobbes by Bill Watterson We gratefully acknowledge the computing time provided on the supercomputer JUROPA at Jülich Supercomputing Centre (JSC), under project HHH20. Thanks partners funding contributed by CFEL LBNL WARP code SCIENCE group Brian McNeil FSP302 BMBF group Johannes Bahrdt group Florian Grüner JUROPA supercomputer
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