چالشهای پیش رو در طراحی و ساخت چشمه‌های نوری با گسیلندگی کم مرتضی جعفرزاده

Main parameters of the storage ring

Third Generation Synchrotron Facilities ESRF 6 GeV France ALS 1.9 GeV USA APS 7 GeV USA BESSY II 1.7 GeV Germany ELETTRA 2.0 GeV Italy SPring-8 8 GeV Japan MAX II 1.5 GeV Sweden SLS 2.4 GeV Switzerland PLS 2 GeV Korea SRRC 1.4 GeV Taiwan SSRL 3 GeV USA CLS 2.9 GeV Canada Soleil 2.5 GeV France Diamond 3 GeV UK ALBA 3 GeV Spain

NameLocationEnergy (GeV) TPSTaiwan3 NSLS IIUS3 SESAMEJordan2.5 ILSFIran3 SIRIUSBrazil3 TACTurkey3

Survey of low emittance lattices

Emittance, what is it ?  = Area in x, x’ plane occupied by beam particles divided by π

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)

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 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 Storage ring based light sources

Small aperture vacuum chamber 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)

Vacuum chamber Strong magnet field quadrupole and sextupole  small aperture for vacuum chambers Nox(mm)y(mm)Nox(mm)y(mm)

Enabling technology Compact magnet and vacuum technology Precision magnet pole machining for small aperture magnets, combined function magnets, tolerance for magnet crosstalk (e.g. MAX-Lab) NEG-coated vacuum chambers enable small apertures to enable high magnet gradients Pioneered at CERN, used extensively at Soleil, and adopted for MAX-IV and Sirius MBA lattices

Basic Mechanical Layout 22 Three-fold symmetry with one horizontal air gap where the back leg is removed to accommodate the antechamber (type A); Segments of the sextupole are connected with return yokes (type B); Type A Type B

Magnetic Field Calculations 23 Field Gradient ; Field Quality ; Magnet Cross Section with Field Lines by Poisson &FEMM ;

Electrical & Cooling Parameters ParameterUnitResultParameterUnitResult Physical length (B)m0.344Resistance per coil10.3 Total amp-turns per coilA.t2957Resistance per magnet61.7 Operating currentA140.8Voltage drop per magnetV8.67 Number of turns per coil-21Power per magnetKW1.22 Number of pancakes per coil-NothingNumber of water circuits-3 Conductor dimensionsmm6.5*6.5Water temperature riseC5.81 Water cooling tube diametermm3.5Cooling water speedm/s1.74 Copper area Pressure dropbar6 Current density4.32InductancemH14.98 Specific resistance Reynolds number Hollow conductor coils cross section ;

Correctors and Sextupoles 25 -Maximum strength of dipolar correctors used for orbit correction is about mrad. >> B=4.8 mT -The rms value of correctors strength for each seed is less than 45 μrad. Strength of the corrector magnets for 100 seeds of random error ; Distribution of correctors as trim coils on the sextupoles within a super period; A & B type magnets & Max distance of the edge of chamber & antechamber from the center of each magnet ;

Correctors and Sextupoles Horizontal corrector (blue), Vertical corrector (red), and Skew quadrupole (purple) coils 26 Type A with spacers filled by the same yoke material ; Type B with return yokes;

Correctors Field Distribution 27 Horizontal Correctors ; Vertical Correctors ; Skew quadrupole Correctors ; g=0.08 T/m

Air-cooled trim coils(mm) ; Electrical Parameters 28 Parameters Horizontal Corrector Vertical Corrector Skew Quadrupolar 3 GeV(mrad) Magnetic field (T)4.8E E -3(field on pole tip) Effective length (mm)360 Ampere-Turns per pole (A.t)4*32 (2) + 4*16 (4)3.5*32 (4)4*16 Turns per coil (I) Conductor size (mm 2 )3.15*0.5 Resistance per magnet (mΩ)736(2)+736(4) Magnet Inductance (mH)21(2)+11.5(4) Current (A)43.54 Total Voltage (V)2.95(2)+2.95(4) Total Power (W)11.8(2)+11.8(4)

Steel Material 29  The high field material could easily replaced by better materials. Din ST14: (International standard number:1.0338) CSiMnPS 0.03 %0.01 %0.24 %0.011 %0.016 % Chemical components of steel  A locally available low carbon steel similar to AISI 1010 steels was chosen.

Thermal absorber 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

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: Δε/ε 0 < 20%  Beam position stability: x y ΔσxΔσx ΔσyΔσy Beam stability requirement

Some measurement results at ESRF  ε x =4 nm  ε y =3.7 pm

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 y =4 pm

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

Records for smallest vertical emittance ( ) APS 0.35 pm Courtesy L. Rivkin PSI and EPFL SLS 0.9 pm

Transversely coherent x-rays - Uniform phase wavefronts: coherent imaging, holography, speckle, etc. - Focusable to smallest spot size: nano-focus - High flux (~ photons/sec) in small spot: slits may not be required, etc. - Round beams: H-V symmetric optics, circular zone plates, flexibility in optics Advanced applications - Coherent diffractive imaging with wavelengthlimited spatial resolution; ptychography - Spectroscopic nanoprobes using powerful x-ray contrast modes: XRF, XAS/XES, ARPES, RIXS - Photon correlation scattering/spectroscopy - Science case continues to be developed Addresses “Grand Challenge Science”

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  Micron or sub-micron beam stability is needed for a USR machine

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 Beam stability requirement

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 Beam stability requirement

Two characteristics to be pointed out Spectral displacement strongly decreases when frequency increases Vibration amplitude varies with time Ground vibration

Data source: W. Bialowons & H. Ehrlichmann, DESY, 2006 R. Bartolini et al., EPAC2008 Soleil private communication IHEP private communication Soleil, Diamond BAPS Huairou site Ground vibration 1 – 100 Hz

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

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

Δx = TF Q2e * f FOFB * TF s2M&G * f damping * TF gr2s * x gr < 0.1σ x Horizontal: (1.0) ~ 0.1 µm Vertical: ~ 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

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

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

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

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

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

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 ( ) 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)