Laser-driven undulator source

Transcription

1 Laser-driven undulator source Matthias Fuchs, R. Weingartner, A.Maier, B. Zeitler, S. Becker, D. Habs and F. Grüner Ludwig-Maximilians-Universität München A.Popp, Zs. Major, J. Osterhoff, R. Hörlein, G. Tsakiris, F. Krausz and S. Karsch Max-Planck-Institut für Quantenoptik T. P. Rowlands-Rees and S. M. Hooker University of Oxford U. Schramm Forschungszentrum Dresden, Rossendorf FLS Workshop, Stanford,

2 Laser-wakefield electron acceleration laser power: ~ TW to PW energy: ~ J pulse length: ~ 5-50 fs gas jet or capillary: plasma acc. gradient: GV/m few cm γ few-100 MeV- GeV electrons M. Fuchs, FLS 2010

3 Duration of the accelerated bunch )*'+,"!&!$-.)/&#,"!$&0&'!"#1"& 2"3$!$-.)/&4/$%$&5&617!"#$%& '(!#$ 9(99!$ 8&$&9(-,/&!$-.)/:&;&61&0&<=&>#?? PIC simulation (M. Geissler) M. Fuchs, FLS 2010

4 M. Fuchs, FLS 2010 Experimental setup: LWFA ATLAS 1 J 35 fs

5 M. Fuchs, FLS 2010 Experimental setup: LWFA ATLAS 1 J 35 fs

6 M. Fuchs, FLS 2010 Measured Electron Spectra at MPQ Electron energy [MeV] Consecutive laser shots

7 M. Fuchs, FLS 2010 Measured Electron Spectra J. Osterhoff, A.Popp, et al.,!"#!!"!"!#$%##&!'&##$(

8 Setup Undulator Radiation M. Fuchs, FLS 2010

9 M. Fuchs, FLS 2010 Setup Undulator Radiation field gradient: 500 T/m aperture 6 mm

10 M. Fuchs, FLS 2010 Setup Undulator Radiation L = 30 cm!u = 5mm K = 0.55 gap = 1.2mm

11 M. Fuchs, FLS 2010 Setup Undulator Radiation! divergence = 2 mrad FWHM pointing stability = 1.4 mrad rms # ($"" (""" (mm) " '"" &"" %""!! $"" #!! "! (mm) "

12 M. Fuchs, FLS 2010 Setup Undulator Radiation 1.32 mrad (mm) 5mm 5 0 no lenses intensity [a.u.] !5 1000!5 with Magnetic 0 Lenses 5 (mm) 2.49 mrad

13 M. Fuchs, FLS 2010 Setup Undulator Radiation 1.32 mrad (mm) 0.12 mrad 0!5 5mm 5 with Magnetic Lenses! mrad with lenses (mm) 2.49 mrad x intensity [a.u.]

14 M. Fuchs, FLS 2010 Setup Undulator Radiation Energy [MeV]

15 Measured Undulator Spectrum w Transmission Grating transmitted radiation (0.th order) ±1st diffraction orders

16 Measured Undulator Spectrum Observation angle (mrad) CCD counts (arb. units) λ res = Wavelength (nm) λ u 2nγ 2 (1+ K2 ) 2 + γ2 Θ 2 0 MF et al., Nature Phys. 5, 826 (2009)

17 Undulator Wavelength vs Electron Energy 40 Undulator wavelength (nm) λ res = Electron energy (MeV) λ u 2nγ 2 (1+ ) K2 2 + γ2 Θ 2

18 Electron- & Undulator Spectrum Electron Undulator spectrum spectrum Counts [arb.units.] % (FWHM) Energy [MeV] λ [nm]

19 Energy-dependent Influence of Magnetic Lenses 1.2 mm horizontal envelopeσ e,x position of CCD 190 MeV 1.2 mm 1.2 mm vertical envelope 1 m σ e,y s undulator beam size: (at position s) Σ und (s) = σ 2 ph (s)+σ2 e(s) 1.2 mm 210 MeV s single electron 1.2 mm electron beam emission 240 MeV 1.2 mm s

20 System Response Function Normalized on-axis flux [arb.units.] Energy [MeV]

21 Filtered Electron Spectrum Counts [arb.units.] % (FWHM) Energy [MeV]

22 Filtered Electron Spectrum Counts [arb.units.] % (FWHM) % (FWHM) Energy [MeV] Undulator λ spectrum λ 1 γ 2 dλ λ 2 dγ γ

23 Tuning of the Undulator Radiation tuning by moving the lens position:! changing the response curve M. Fuchs, FLS 2010

24 Tunability of the Source 1 Normalised on-axis flux [arb. units] Electron energy [MeV]

25 Properties of the Undulator Source #/A)E)AE#/A)&2"3$!$-.)/&3"%+")+A-&A>&FD )(-"9!$&+-&2"3$!$-.)/&9*&,/"-.+-.&!$-#G&'A#+)+A-# 106 photons in the fundamental (whole CCD) on-axis peak intensity: 10,000 photons/(shot mrad2 0.1%b.w.) (1 pc charge in effective spectrum) M. Fuchs, FLS 2010

26 Focussing of Undulator Radiation by Focussing the Electron Beam: (X-ray) lens-less focussing Electron beam trajectories x- plane 5 µm y- plane 5.5 µm 210 MeV, no energy spread M. Fuchs, FLS 2010

27 LWFA-forgiving Setup for Undulator Radiation Applications undulator radiation sample undulator dipole magnet electron beam compact setup possible for short undulator (hard focussing) no lossy X-ray optics necessary for LWFA beams tolerates fluctuations in energy and pointing (unlike for example Bragg-crystals as focussing elements) M. Fuchs, FLS 2010

28 WG8 Charge: Overview Laser Wakefield Accelerator Source Spontaneous Source FEL 500 ev 50 kev Demo-VUV 5 kev Electrons 550 MeV 100 pc 5% 5.5 GeV 300 pc 5% parameters: ongoing research 1.7 GeV 1 nc 0.1% Driverlaser 200 TW 4J /20fs 3 PW 60J /20fs 200 TW 4J /20fs 3 PW 60J /20fs Timeline near term 2 years long term >5 years near term 4 years long term >7 years -> Timeline refers to demonstration of the source and first experiments -> FAR from being user facilities!! M. Fuchs, FLS 2010

29 WG8 Charge: Scaling Laws Design/Timelime Scalings LWFA energy gain: LWFA max. acc. electrons: W P [GW] N max P [GW] Gordienko, Pukhov W. Lu Cost/Efficiency Undulator Design values 500 ev 50 kev FEL Design values 5 kev Demo Problems Solutions 1D FEL theory e-folding length: Pierce parameter: undulator length: JKLM&NOPLQ&4>#&1A@$7 IA (17kA) simulation MPQ test case ρ 1 γ ( I I A σ 2 x ) 1/3 λ 4/3 u L sat (15 25) L gain 1 nc/10 fs = 100 ka M. Fuchs, FLS 2010

30 M. Fuchs, FLS 2010 WG8 Charge: Costs / Efficiencies Design/Timelime Scalings Cost/Efficiency Undulator Design values 500 ev 50 kev Design values 5 kev Demo Problems Solutions Lasers: 200 TW, 4 J / 20 fs state of the art 1.5 M! (Optimistic) Efficiency estimation Wall Plug -> Laser: 10 % consider 60 % into pumping diode Laser -> Electron Beam:10 % => Total Wall Plug Efficiency: 1% 3 PW, 60 J / 20 fs in development 10 M! + vacuum chambers & equipment

31 M. Fuchs, FLS 2010 Spontaneous Undulator Radiation Design/Timelime Scalings Cost/Efficiency Undulator Design values 500 ev 50 kev Design values 5 kev Demo Problems Solutions 5 mm period, K = m undulator (use focussing of photon beam by hard-focussing of electron beam) 500 ev 50 kev electrons energy 550 MeV 5.5 GeV acc length 3 cm 50 cm norm. emittance 1 mm mrad 1 mm mrad charge 100 pc 300 pc energy spread 5% 5% photon beam pulse duration 10 fs 10 fs peak ph/sec/0.1% b.w. 8.4 * *10 18 av. ph/sec/0.1% b.w. 8.4 * *10 4 laser power 200 TW 3 PW rep. rate 10 Hz 1 Hz

32 FEL: Design Values Design/Timelime Scalings Cost/Efficiency Undulator Design values 500 ev 50 kev Design values 5 kev Demo Problems Solutions 5 mm period, K = m undulator: saturation 5 kev Demo-VUV electrons energy 1.7 GeV?? acc length 15 cm?? emittance 1 mm mrad?? charge 1 nc?? energy spread 0.1%?? photon beam Pierce parameter 0.15% pulse duration 4 fs?? peak ph/sec/0.1% b.w. 1 *10 26?? av. ph/sec/0.1% b.w. 4 *10 11?? laser power 3 PW 200 TW rep. rate 1 Hz 10 Hz )*!+,-./,!$%&'()"!*++()&!,-.)&/!'&##0(* - no wakefield-effects in undulator included - no start-2-end simulation M. Fuchs, FLS 2010

33 M. Fuchs, FLS 2010 Problems Design/Timelime Scalings Cost/Efficiency Undulator Design values 500 ev 50 kev Design values 5 kev Demo Problems Solutions stability (MPQ*) - pointing: 1mrad (rms) - variation in charge: 40 % - variation in energy: 6 % energy spread 3.5 % (rms) => FAR from being user facility!! need more accelerated charge (up to 1 nc) higher electron energies * J. Osterhoff, A.Popp, et al.,!"#!!"!"!#$%##&!'&##$(

34 Solutions Design/Timelime Scalings Cost/Efficiency Undulator Design values 500 ev 50 kev Design values 5 kev Demo Problems Solutions Stability MORE LASER POWER (not driving the driver laser at its spec-limits) -> decrease fluctuations Decouple injection from acceleration: counter-prop. pulses density downramp n Principle: Plasma wave courtesy: V. Malka Injector: plasma ramp courtesy: W. Leemans electrons Pump beam z Injection beam More charge/ higher electron energies MORE LASER POWER LOA: 1%-rms energy spread (10 pc) C.Rechatin et al, PRL 102 (2009) LBNL: nc from backside of gasjet low longitudinal and transverse momentum C.Geddes et al, PRL 100 (2008) M. Fuchs, FLS 2010