Design of Photon Beamlines at the European XFEL

Transcription

1 Design of Photon Beamlines at the European XFEL Harald Sinn (THOCI1) FEL 2010 Malmö August 26, 2010

2 Construction progress at the European XFEL Experimental Hall in Schenefeld Injector building at DESY

3 X-ray Beam Transport 3 Photon Beamlines SASE 1 photon beamline

4 Beamline Layout for SASE1 and SASE2 4

5 Mirror technology 5 Problem: Mirrors are too short! Coherent beams require height-height correlation (absolute shape error) of less than 2 nm PV over entire length (Strehl-ratio 0.8) Currently only two suppliers (JTEC and ZEISS) with proven record of deterministic polishing to nm-scale Only few (short) mirrors on nm-flatness scale existing. Upper length limitation 500 mm-800 mm deterministic polishing atomic removal process + metrology substrate support

6 Mirror technology: Finite lengths 6 Simulation of beam spot in experimental hall 6 σ 2 nm PV flatness 4 σ 2 σ

7 Measurements of Beam Divergence at LCLS in 2009 (8.3 kev) (Welch, Turner, Emma, Sinn, )

8 Lower Emittance: Higher Divergence 8 poster MOPC05 E. Schneidmiller and M.V. Yurkov low Q (20pC) used for beam line optimization (1.5 theory)

9 Offset mirror geometry (SASE 1) 9 Try to get mirrors as close as possible to source to maximize beam coverage z_offset2 x_deflect = 50 mm z_source z_offset1 425 m

10 Offset mirror geometry (SASE 1) SASE mrad 4σ 3σ 5σ 10 z_offset2 2σ x_deflect = 50 mm z_source z_offset1 theoretical divergence (0.1 nc) x 1.5

11 Offset mirror geometry (SASE 1) SASE mrad 1.5 mrad 1.1 mrad 4σ 3σ 5σ 11 shifting 2σ θ 100 μrad z_offset2 x_deflect = 100 mm z_source z_offset1 theoretical divergence (0.1 nc) x 1.5

12 Distribution mirror geometry (SASE 1) 12 angle adjustment XTD 9 Problem: incident angle cannot be adjusted 1.45 m 425 m 465 m 960 m

13 Distribution mirror geometry (SASE 1) 13 XTD 9 focusing (20 km) 1.45 m defocusing 425 m 465 m 960 m Solution: focus behind distribution mirror

14 Damage at offset mirrors with converging beam 14 parallel beam converging beam (same energy) X-ray penetration remains same diverging beam converging beam Conclusion: focusing behind distribution mirror does not lead to increased damage, as long as footprint on mirror remains the same

15 Ray tracing for SASE 1 (800 mm mirrors) SASE1: E =5-20 kev 15 kev range 5-18 shift: 120 mm SASE2: E =3-24 kev 3-22 shift: 150 mm

16 E[keV] Design of Photon Beamlines at the European XFEL Transmission of proposed SASE1&2 geometries mm (optical length) mirrors, min. 4 σ acceptance accessible energy range without shifting or bending change mirror angles and bending 0 left SASE 1 center right left SASE 2 center right

17 Special requirements optics at European XFEL 17 XFEL pulse pattern: 99.4 % empty 0.1 s 0.6 ms 0.1 ps 30 W 10 kw 20 GW 40,000 W/mm 2

18 First offset mirror (SASE2) 18 water cooling: ± 20 nm deformation under 22 W load water cooled copper bar indium-gallium coating silicon substrate kinematical mount

19 Beam aperture in front of mirrors 19 Conceptual Design SASE 1. Steady State (Temp at the cooling channels ~43 C) Possibility to tilt the blades Blade Geometry and Materials SASE 1. Transient (Hottest Spot Temp ~1050 C)

20 Diamond Laue Monochromator 20 collaboration with: Diamond Materials, Fraunhofer Institut Freiburg and Element6 Stress relief: laser cutting

21 Diamond Laue Monochromator 21 initial temperature

22 Expanded Beam Monochromator 22 offset and distribution mirrors Si (111) mono 10 mm 0.05 K/shot 0 m 400 m 800 m 900 m

23 Expanded Beam Monochromator 23 offset and distribution mirrors Si (111) mono 10 mm 0.05 K/shot 0 m 400 m 800 m 900 m

24 Summary 24 A beam distribution system is proposed that can deliver 3-24 kev beam to central and branch experimental stations based on 800 mm long mirrors: Adjustment to beam size by mirror incident angle Intermediate focusing on distribution mirrors Nice side effects: Cut-off of higher harmonics and defocusing at monochromators possible. For mirrors, water cooled seems sufficient Monochromators will be diamond or in the expanded beam silicon (cryo-cooling)

25 Acknowledgements 25 European XFEL Optics group: Shafagh Dastjani-Farahani, Idoia Freijo-Martin, Germano Galasso, Jerome Gaudin, Liubov Samoylova, Antje Trapp and Fan Yang LCLS commissioning team: Paul Emma, James Welch + many others

26 Thank you for your attention! 26