1. Design Considerations of table-top FELs laser-plasma accelerators principal possibility of table-top FELs possible VUV and X-ray scenarios new experimental status critical points review cooperation with DESY… LMU: F. Grüner, U. Schramm, S. Becker, R. Sousa, T. Eichner, D. Habs MPQ: S. Karsch, M. Geissler, L. Veisz, J. Meyer-ter-Vehn, F. Krausz UCLA: S. Reiche DESY, June 20; recap of FLS 2006, May 15, 2006

2. Laser-Plasma accelerators: “bubble acceleration” TW laser, 5-50 fs electron bunch: e.g. 170 MeV (LOA), 1.2 GeV (Berkeley)

3. M. Geissler PIC code 5fs, a=5

4. ~4 cm 300 µm electrodes gas-filled capillary Discharge capillaryyear laser pulse energy Pulse length electron energy energy spread divergence2004 0.36 J 40 fs 86 MeV 2 % 3 mrad 2006* 1.3 J 33 fs 1.2 GeV < 2% 1.6 mrad * presented at Anomalous Absorpt. Conf., June 6, 2006; submitted to Science MPQ: since two weeks 0.35 J in 37 fs, soon 1-2 J future (~2009): 5 J, 5 fs (=1 PW), 1 kHz Leemans laser-plasma- acceleration

5. Improvement by capillaries discharge introduces parabolic electron density laser guiding beyond Rayleigh length → higher energies de-phasing: reducing energy spread ion-channel: reducing electron beam diameter and divergence possible scenario: bubble turns into linear wakefield → GeV- energies with ~0.1% energy spread started cooperation with Simon Hooker (Oxford) de-phasing

6. Important feature: ultra-high current laser pulse ~ 2 µm only!! ~ nC charge ~ 100 kA typical length scale = plasma wavelength

7. Principal possibility for table-top FELs current beam diameter (optimal!) : few 100kA (classical: 5 kA) und. period : few mm (class. few cm) simplest estimate: ideal 1d Pierce parameter (no energy spread, emittance, diffraction, time-dependence)

8. reduction in λ u allows a reduction in γ, but needs ultra-high current for keeping ρ and also saturation power large enough DESY flash (fs mode): λ u = 27 mm (462 MeV) ε n = 6 mm·mrad ΔE/E = 0.04 % saturation length (Xie Ming) for SASE VUV FEL @ ~28nm Λ (Xie Ming) MPQ (GENESIS) λ u = 3 mm (133 MeV) ε n = 1 mm·mrad ΔE/E = 0.5 % Constraints for table-top FELs not only table-top size, but sufficient output power:

9. Start-to-End Simulations own 3d PIC code electron bunch transport/ focusing/ filter FEL undulator laser GPT, Geant CSRTrack, Spur; GENESIS 1.3

10. A possible first VUV case Parameter DESY (flash, fs-mode) MPQ Current 1.3 kA 160 kA Norm. Emitt. (rms) 6 mm·mrad 1 mm·mrad Energy 461.5 MeV 130 MeV Energy spread 0.04 % 0.5 % Wavelength 30 nm 25 nm Pierce par. 0.00160.0117 Sat. Power 0.66 GW 5 GW Sat. Length 19 m 45 cm

11. International competition and a possible first table-top XFEL case Parameter Leemans (FEL2005 conf.) 100 TW, 33 fs MPQ (TT-XFEL) 1 PW, 5 fs Current 25 kA 160 kA Norm. Emitt. (rms) 1 mm·mrad Energy 1 GeV 0.9 – 1.2 GeV Energy spread 1 % 0.1 % Und. Period 10 mm 1.5 – 3 mm Wavelength 2 nm 0.25 nm Und. length 4.7 m 3 m

12. New Experimental Status undulator: 60 periods, 5 mm period, 1.6 mm gap ~1 T field on axis few days ago: 40 MeV electrons

13. Critical Points Review space charge influence due to ultra-dense bunches - HOMDYN (L. Serafini): for 1 GeV correlated energy spread 0.5 %, no debunching - GPT/CSRtrack runs (see next talk) - simple analytical estimates in agreement with GPT - linear energy chirp can be compensated with tapering transverse coherence - valid only for spontaneous source, here: gain guiding - calculate growth rate of next higher mode with GENESIS - transverse coherence important for focusing only? peak brilliance: 10 32 @ 5 keV - comparable with LCLS! (10 12 phts/0.1%BW, θ =15µrad, σ x =30µm, τ =10fs)

14. Cooperation with you… verify our GPT results with ASTRA verify entire feasibility study (publishing a joint paper) discuss beam features in detail (slice energy spread, etc.) for experiments: diagnostic methods (FROG) open questions, such as maximum photon energy what could you learn from us????