1. Slide: 1 Workshop on Accelerator R&D for USR Beijing, 30 Oct – 1 Nov., 2012 Some engineering considerations for USR light sources L. Zhang European Synchrotron Radiation Facility  Vacuum chamber and thermal absorber  Beam stability requirement  How to reach beam stability  Heat load issues for beamline optics

2. Slide: 2 Workshop on Accelerator R&D for USR, Beijing, 30 Oct – 1 Nov., 2012,Engineering considerations / L. ZHANG Emittance in present and future light sources R. Bartolini, DLS, LowERing 2011, Crete ε z ~ pm.rad routinely in many LS ε x ~ nm.rad  sub-nm.rad ε x  100 pm.rad USR (diffraction limited)

3. Slide: 3 Workshop on Accelerator R&D for USR, Beijing, 30 Oct – 1 Nov., 2012,Engineering considerations / L. ZHANG Storage ring based light sources Ultimate storage ring:  Diffraction limited emittance: pm.rad  New lattice based on MBA: Lattice design  Challenging magnet design and manufacturing Some engineering issues (challenges):  Vacuum chambers  Thermal absorbers  Stability (mechanical, thermal, beam, BPM, magnets,…)  Heat load issues for beamline optics

4. Slide: 4 Workshop on Accelerator R&D for USR, Beijing, 30 Oct – 1 Nov., 2012,Engineering considerations / L. ZHANG Challenging issues ESRF ANNUAL WORKSHOP ON MACHINE RELATED ACTIVITIES Château de Sassenage, Monday 29th January 2001 ULTIMATE STORAGE RING X-RAY SOURCE – A Ropert A. Ropert et al., Proceedings of EPAC 2000

5. Slide: 5 Vacuum chamber Strong magnet field quadrupole and sextupole  small aperture for vacuum chambers Workshop on Accelerator R&D for USR, Beijing, 30 Oct – 1 Nov., 2012,Engineering considerations / L. ZHANG K.Fukami et al., Low Emittance Ring 2011 P.Raimondi: Emittance Gymnastic Studies, 2012 Spring8 upgrade projectESRF upgrade project 20 ~ 30 mm in diameter

6. Slide: 6 Small aperture vacuum chamber Workshop on Accelerator R&D for USR, Beijing, 30 Oct – 1 Nov., 2012,Engineering considerations / L. ZHANG Issues to be addressed :  Vacuum conductance due to small aperture: 20~30 mm in diameter ―Comparable to some Insertion device vessel (8x58) ―But higher heat load to be managed than ID vessel  NEG coating to be used for pumping and lowering the photon desorption yield (like ESRF ID vessel)  NEG coated vacuum chamber ―Time consuming for NEG coating (~ 10 days for a vacuum chamber) process ―Limited coating production capability in the world  long procurement time ―(costs) ―Activation system to be considered during the vessel design stage Al 6060 NEG coated (8x58)

7. Slide: 7 Thermal absorber Workshop on Accelerator R&D for USR, Beijing, 30 Oct – 1 Nov., 2012,Engineering considerations / L. ZHANG Issues to be addressed :  Distributed absorbers – to protect vacuum chamber ―Limited space (2 dipoles  7 dipoles per cell) ―Al-extruded vacuum chamber with cooling integrated, or with anti-chamber ?  Crotch absorber ―Limited space ―Lower dipole field, less power  possible to use OFHC copper instead of Glidcop, but design to be optimized ―ESRF 2 nd Generation crotch absorber: T max /3, S max /3.5 ―Advantages to use OFHC copper instead of Glidcop:  Procurement and cost  Easy brazing Compact Easy to manufacture No brazing interface on the thermal path Water cooling channel off X-ray path Possibly in OFHC copper Double slope design T max /3, S max /3.5

8. Slide: 8 Small emittance  small beam size Beam size ~ f(emittance, β-function, energy spread σ γ and dispersion function η):  RMS beam size:  RMS divergence: Beam position motion   Larger apparent beam  Macroscopic “emittance growth” Beam stability requirements  Emittance growth: Δ ε/ε 0 < 20%  Beam position stability: x y ΔσxΔσx ΔσyΔσy Beam stability requirement Workshop on Accelerator R&D for USR, Beijing, 30 Oct – 1 Nov., 2012,Engineering considerations / L. ZHANG

9. Slide: 9 Some measurement results at ESRF Workshop on Accelerator R&D for USR, Beijing, 30 Oct – 1 Nov., 2012,Engineering considerations / L. ZHANG  ε x =4 nm  ε z =3.7 pm

10. Slide: 10 Some measurement results at SOLEIL Workshop on Accelerator R&D for USR, Beijing, 30 Oct – 1 Nov., 2012,Engineering considerations / L. ZHANG  ε x =3.91 nm  ε z =4 pm

11. Slide: 11 From measurement results to extrapolation results  Only reducing emittance  “Keeping” all other parameters unchanged (not true for some of them)  Beam stability issue should be addressed to limit the emittance growth for low-emittance or diffraction limited storage ring Beam stability requirement for USR Workshop on Accelerator R&D for USR, Beijing, 30 Oct – 1 Nov., 2012,Engineering considerations / L. ZHANG

12. Slide: 12 Mechanical (vibration) stability  Ground vibration  Slab design and manufacturing  Magnet-girder assembly  Damping devices Storage ring  Lattice optic (vibration) amplification  Fast orbit feedback Thermal stability  H=1.4m,steel structure, ΔT=0.1°C  ΔH=2.4 μm  Temperature stability in time and in space Thermal, mechanical stability for BPM (support), for beamline,… Beam stability related parameters Workshop on Accelerator R&D for USR, Beijing, 30 Oct – 1 Nov., 2012,Engineering considerations / L. ZHANG  Micron or sub-micron beam stability is needed for a USR machine

13. Slide: 13 Vibration transmission path slab magnet Girder Brilliance reduction Emittance growth e-beam motion (time-dependent orbit oscillation) Magnet vibration Girder Vibration Ground vibratio n Transfer functions TF Q2e TF G2M TF s2G TF gr2s x gr Workshop on Accelerator R&D for USR, Beijing, 30 Oct – 1 Nov., 2012,Engineering considerations / L. ZHANG Beam stability requirement

14. Slide: 14 Design and optimization to reach the stability criterion: Δx =TF Q2e * TF G2M * TF s2G * TF gr2s * x gr Ground vibration Slab design Magnet girder design Storage ring Lattice design Δx = TF Q2e * f FOFB * TF s2M&G * f damping * TF gr2s * x gr < 0.1σ x Slab design Fast orbit feedback ( f FOFB ) Damping device ( f damping ) < 0.1σ x Workshop on Accelerator R&D for USR, Beijing, 30 Oct – 1 Nov., 2012,Engineering considerations / L. ZHANG Beam stability requirement

15. Slide: 15 Two characteristics to be pointed out  Spectral displacement strongly decreases when frequency increases  Vibration amplitude varies with time Workshop on Accelerator R&D for USR, Beijing, 30 Oct – 1 Nov., 2012,Engineering considerations / L. ZHANG Ground vibration

16. Slide: 16 Data source: W. Bialowons & H. Ehrlichmann, DESY, 2006 R. Bartolini et al., EPAC2008 Soleil private communication IHEP private communication Soleil, Diamond BAPS Huairou site Workshop on Accelerator R&D for USR, Beijing, 30 Oct – 1 Nov., 2012,Engineering considerations / L. ZHANG Ground vibration 1 – 100 Hz

17. Slide: 17 Overview on magnet-girder assembly Workshop on Accelerator R&D for USR, Beijing, 30 Oct – 1 Nov., 2012,Engineering considerations / L. ZHANG Magnet-girder assembly

18. Slide: 18 Test results (2001) at ESRF Lattice optic (vibration) amplification factor reacheable:  TF Q2e (H) ~ 31  TF Q2e (V) ~ 12 L. Zhang et al., PAC2001 Workshop on Accelerator R&D for USR, Beijing, 30 Oct – 1 Nov., 2012,Engineering considerations / L. ZHANG Electron beam stability Bartolini et al., Proceedings of EPAC08 JM Filhol, Rayon de SOLEIL #16 - April 2008

19. Slide: 19 Δx = TF Q2e * f FOFB * TF s2M&G * f damping * TF gr2s * x gr < 0.1σ x Horizontal: 301.4 (1.0)1.00.02 ~ 0.1 µm Vertical:101.01.00.02 ~ 0.1 µm state-of-the-art Workshop on Accelerator R&D for USR, Beijing, 30 Oct – 1 Nov., 2012,Engineering considerations / L. ZHANG Beam stability summary Only incoherent part (in space) to be considered ( > 5 or 10 Hz ? )  significant lower Cooling water flow induced vibration

20. Slide: 20 Photon beam vs emittance reduction Example of ESRF machine (6GeV, 200mA) with an undulator U27, K=1.48 photon brilliance, photon flux Workshop on Accelerator R&D for USR, Beijing, 30 Oct – 1 Nov., 2012,Engineering considerations / L. ZHANG

21. Slide: 21 Photon beam vs emittance reduction Example of ESRF machine (6GeV, 200mA) with an undulator U27, K=1.48, L=5.8m, at 32 m from the middle of straight section Power distribution: Consequences of emittance :  Brilliance increase (inversely proportional)  Photon flux unchanged, slight modification of the spectral flux  Total power from undulator unchanged  Comparable power distribution as in high-β section  Higher power density and smaller photon beam size than in the present low-β section Workshop on Accelerator R&D for USR, Beijing, 30 Oct – 1 Nov., 2012,Engineering considerations / L. ZHANG

22. Slide: 22 Heat load issues for beamline optics Basically, the power distribution of an USR is similar to the present SR in High- β section  Heat load for beamline optics can be handled: ―Water cooling for white beam mirror (top side cooling, smart cross section, fully illumination along the mirror) ―Liquid nitrogen cooling for Silicon monochromator crystal (full side cooling) For ESRF beamlines in low-β section, low emittance ring   Higher power density and smaller photon beam size  Some high heat load optical components to be revised, especially white beam mirror, and multilayer optics Workshop on Accelerator R&D for USR, Beijing, 30 Oct – 1 Nov., 2012,Engineering considerations / L. ZHANG

23. Slide: 23 Workshop on Accelerator R&D for USR, Beijing, 30 Oct – 1 Nov., 2012,Engineering considerations / L. ZHANG Solution to limit thermal deformation  Water cooling on top side  Cross-section: smart cut  Over-illumination  Secondary slits  The cross section shape is optimised for specific power distributions.  Smaller beam size  different optimised mirror shape L.Zhang et al., SRI2012 Mirror with fully illuminated beam along the mirror 2nd Slits Re-defining the useful beam size remove the “end effects” Primary Slits White beam mirror or Multilayer optics

24. Slide: 24 Workshop on Accelerator R&D for USR, Beijing, 30 Oct – 1 Nov., 2012,Engineering considerations / L. ZHANG Some engineering issues have been reviewed:  Vacuum chambers ―small aperture ―heat load management  Thermal absorbers ―less or comparable heat load than actual 3G light sources ―less space available ―design optimization  Beam Stability ―Challanging for USR: <20% emittance growth, <10% beam size variation ―Efforts needed in the design and manufacturing of slab, magnet girder assembly to limit ground vibration amplification ―To be further investigated: Impacts of cooling water flow induced vibrations, incoherent part of the floor vibration  Heat load issues for beamline optics ―Heat load issues can be managed for beamline optics Summary

25. Slide: 25 Workshop on Accelerator R&D for USR, Beijing, 30 Oct – 1 Nov., 2012,Engineering considerations / L. ZHANG Some other engineering issues have to be addressed:  Mechanical engineering for Magnets ( http://www.bnl.gov/nsls2/workshops/docs/041212_Magnet_Workshop/ )  Thermal stability for mechanical supports (magnet-girder, BPM,…)  Alignment accuracy  Beamline optic stability (thermal and mechanical) for coherence preservation  Is it possible to reduce the lattice optic amplification TF Q2e ?  How to improve the FOFB efficiency ?  How to satisfy large beam requirement for certain beamlines (medical, tomography,…) ?  …… Summary (2)

26. Slide: 26 Acknowledgement P. RaimondiASD director, ESRF L FarvacqueASD, ESRF K ScheidtDiagnostics group, ASD, ESRF E PlouvierDiagnostics group, ASD, ESRF F EpaudISDD, ESRF M. HahnVacuum group, TID, ESRF H. Pedroso MarquesVacuum group, TID, ESRF P. MackrillBIG, TID, ESRF JM Filhol:Formal Deputy director, Soleil (ITER) JL Marlats:Head of MEG, Soleil N Hubert:Diagnostics group, Soleil A Fournol:AVLS And many other colleagues from different light sources Workshop on Accelerator R&D for USR, Beijing, 30 Oct – 1 Nov., 2012,Engineering considerations / L. ZHANG