PHANGS,5-12-2017

Beamline design issues related to the future SOLEIL upgrade

François PolackSynchrotronSoleil

PhotonsAttheNextGenera4onStorageringsTrieste,December5th,2017

outline

•  Present/upgradedsource–  Electron/photonssourceparameters

•  Lightcollec4on–  CollecEonefficiency–  Unwantedlight:heatload

•  Tolerances–  Stability–  OpEcsquality

•  Somecasestudies

PHANGS,5-12-2017

Machine parameters SOLEIL/ Upgrade

PHANGS,5-12-2017

βx (m) β z (m) ηx (m) Long SS 10 8 0.2 Medium SS 4 1.8 0.13 Short SS 18 1.8 0.28 Upgrade 1 1 0

Natural horizontal emittance = 3900 à 72 pm.rad Energy dispersion = 1.03 / 0.86 10-3

Coupling = 1% /100%

SS long medium short upgrade

σx (µm) 281 182 388 7

σz (µm) 17.3 8.1 8.1 7

σ’x (µrad) 19.2 30 14.5 7 σ’z (µrad) 2.2

4.6 4.6 7

Courtesy P. Brunelle

From electron to experiment

PHANGS,5-12-2017

•  Photonsourceemi=ancegain –  electronemiOancegainis~4103–  Whatistransfertothephotonsource?

•  Whatwillbethebenefitforbeamlines?–  Smallerbeamsizeonsample

higherflux/unitarea(illuminaEon)highcoherencefracEon

–  BeOerfluxcollecEon–  SmalleropEcssize–  OpEcssimplificaEons:

lesselements,shorter,morestable,beamlines–  RequirementsonopEcsquality

Monochromatic Photon emittance

PHANGS,5-12-2017

•  Photonsource=Electronbeam+Undulator•  Independentconvolu4onofdivergenceandsourcesizecontribu4ons

forcentralconeσ’ph≈√𝜆/𝐿   σph≈√𝜆 𝐿  /4 𝜋 (diffrac(onlimit)

•  Parametersfora4mlongundulator

•  Electronandphotonsourcesizeanddivergenceconvoluteindependently

•  Energyspreadwidening

⟹ shift emission peak @ λ

Energy 300 eV 3 keV 30 keV σph (µm) 10 3.2 1 σ’ph (µrad) 32 10 3

22 2

2 12 2u Kλ

λ γ θγ

⎛ ⎞= + +⎜ ⎟

⎝ ⎠

2

12 2N E KE

θγ

⎛ ⎞ΔΔ ≈ +⎜ ⎟

⎝ ⎠~10-20µrad

coherence

Beamlines from a designer point of view

Wewanttopreservethesmallsourcesizethroughoutforso`X-raystohardX-rays

Weusedtorelymostlyonreflec4veop4csBecausetheyareachromaEcWhatdoweneedtochange?

PHANGS,5-12-2017

collection monochromation focusing Source Sample

collection monochromation re-focusing Source Sample slit

Elimination of 1st optics vignetting

•  Smalldivergencebeamshavelongwaists

⟹ waist length ~ 3 �/�′

–  Withpresentβ>10mandnonzerohorizontaldispersion,thefirstopEcsat20miso`envignedngonhighenergyBL

•  Withβ=1m–  AllopEcsareinthefarfieldofthesource–  SizeoftheopEcsmatchthesourcedivergence

PHANGS,5-12-2017

( )22 20 Zσ σ σ ʹ= +

Thermal load

•  TotalradiatedPower

•  OnaxisPowerdensity

Expectedincrease

L⟶ x 2 ; 𝐵↓0 ⟶ x 1.5 Power density do not depend on electron beam size and divergence But useful collection aperture does. Reduction of the collection aperture in hard X-rays

PHANGS,5-12-2017

[ ] [ ] [ ] [ ] [ ]0

2 20.633P kW E GeV B T I A L m=

[ ] [ ] [ ]2 40/ / 10.84dP d W mrad B T E GeV I A N⎡ ⎤Ω =⎣ ⎦

Undulatorlength

Numberofperiods

Stability issues

•  Stabilityrequirementsscalewiththesourcesize–  Ontheupgradedmachinetheywillbe~7µminbothplanes–  ThisisalmostthepresentverEcalsize–  Stabilitylevelrequiredforthe1stopEcsat20m:

0.5µminposiEon;10-20nradinangle

•  Presentlymostbeamlinearesensi4vetover4calthermaldriPs–  Improvementofthehutchestemperaturestabilityand–  morerigorousmechanicaldesignrequested

•  Vibra4onstability–  AngularvibraEoninducedbythecoolingsystemsarethemostcriEcal.–  RigidityofthecoolinglinesishardlycompaEblewithpreciseposiEonand

angleadjustmentoftheopEcsunderbeam.–  Thermo-mechanicalengineeringishighlyrequired

PHANGS,5-12-2017

Mirror slope errors

•  Mirrorimperfec4onscanbecharacterizedbyslopeerrors–  Smallwavelengths⟶ geometricalopEcs–  Imagewidening∝focusdistance(q)

•  TangenEal:wt=2σ’tq•  SagiOal:ws=2σ’ssinθq

Twowaysofreducingslopeerrorinfluence1.   Chooseashortfocusdistance

–  Focusingstageonly–  Diaphragminaintermediateimagemayhelpdecoupling

beamlineopEcsinfluence(fluxcost)2.   Usesagi=alfocusinggeometry

–  OnlyinthemostsensiEve(dispersion)direcEon–  Widelyusedonpresentmachineduetosourcesizeasymmetry

•  UpgradedSOLEILwillrequire4ghtertangen4altolerancesSourceat20m&σh=7µm⟹ σ’t << 0.2 µrad

PHANGS,5-12-2017

Source σ’

p

2σ’p

q 2σ’q

θ

Wavefront preservation

•  Lightsca=eredfromwavefrontimperfec4ons–  Reducespeak(specular)intensity;generateahaloaroundit.

•  WavefrontqualityoPenexpressedbyStrehlra4o𝑆= 𝒔𝒑𝒆𝒄𝒖𝒍𝒂𝒓 𝒇𝒍𝒖𝒙/𝒕𝒐𝒕𝒂𝒍 𝒇𝒍𝒖𝒙 = (𝒕𝒐𝒕𝒂𝒍 𝒇𝒍𝒖𝒙 −𝒔𝒄𝒂𝒕𝒕𝒆𝒓𝒆𝒅 𝒇𝒍𝒖𝒙)/𝒕𝒐𝒕𝒂𝒍 𝒇𝒍𝒖𝒙 =1–TIS(TotalIntegratedSca5er)

•  Sca=erisrelatedtothepowerspectraldensityofphasefluctua4ons𝑇𝐼𝑆=𝑒𝑥𝑝(−2� �↓� )↑2 =𝑒𝑥𝑝(−2� �↓� ⁄� )↑2 �↓� ↓↑2 =varianceofopEcalpathFor imaging : 𝑆 >0.8 ⟺ �↓� ↓↑2 > �↑2 /180 Maréchalcriterion

PHANGS,5-12-2017

Diffraction limited optics

•  Forfocusing:phaseerrorsmustmeetMaréchalcriterion

–  (totalforallsurfaces)

–  Tolerancesarerelaxedbygrazingangle

–  RoughesEmateusingθ=θc/2forsimplemetalcoaEng

PHANGS,5-12-2017

2 sin14hλ

θσ σΔ = <

h θ

1000 100000

1

2

3

4Max height error for diffraction limit at 1/2 θc

Max

hei

ght e

rror (

nm R

MS)

Energy(eV),

Ir Pt Rh Pd

0.1

1

10

Gra

zing

angl

e (d

eg)

1/2 θc

Consequences of small grazing angles

•  Incidencechangesalongacurvedsurface

–  Difficulttoexceed±30%ofcentralvalueθ0Ø  ImageapertureangleNA<0.3sinθ0

•  Reducedapertureangleimpactsspa4alresolu4onMinimumfocussizeisinverselyproporEonaltoapertureangleevenforaperfectsurfaceeg:E=20keV;grazingangle0.09deg⟹ NA= 0.47 10-3 ρ = 66 nm Transverseaperturesizeisalsoverysmalleg:F=100mm⟹ aperturesize=100µm

PHANGS,5-12-2017

/ 2NAρ λ=

Multilayer coatings

•  Tuningcondi4on

•  StandardmaterialpairsMo/B4CCr/B4CW/B4C

•  Stabledownto~2.5nmperiod

•  Bandpass/reflec4vitytradeoffNumberofeffecEveperiods

PHANGS,5-12-2017

2 22 cos2 sin c

m nm ifλ θ

λ θ θ θ

= Λ −

= Λ >>

FromC.Morawe,ESRFFridayseminar25-05-10

Multilayer / single layer mirror

Single layer multilayer

Grazing angle θ ~ �/35 𝑛𝑚  �/2�  < �/4 𝑛𝑚 

Max Aperture ~ θ/3 < �/100 𝑛𝑚  < �/12 𝑛𝑚  requires ML gradient

Ultimate Resolution 50 nm 6 nm RMS shape errors (Maréchal)

< 1.3 nm < 0.15 nm

PHANGS,5-12-2017

Mirror quality progress

•  SOLEILBeamlinemirrors–  Conven4onalpolishing+Ionfiguringcorrec4on–  BesttangenEalRMSslopeerrorsonlength200–300

2006: 0.5µrad2011: 0.25µrad2016: 0.23µrad

–  FluidJetpolishing

2014: 50nrad(0.2nmRMS)-length300mm

–  Fluidjetpolishingismasteredbyonemanufactureronly!

Mirrorsaretheonlyachroma4cX-rayop4cs–  AlsorequiredasblanksfornonachromaEcopEcs:

graEngsandmulElayermirrors

PHANGS,5-12-2017

Effect of shape errors on a fully coherent beam

PHANGS,5-12-2017

CourtesyDanieleCocco(SLAC)

BeamonLCLSCXIstaEononMay2017NewKBmirrors,1mlong,fluidjetpolished0.3nmRMSmeasuredbymanufacturer(0.5nmmeasuredatLCLS)

BeamonLCLSCXIstaEononSept2016KBmirrorsare450mmlongwith2nmRMSshapeerrors.

Laboratory Metrology

PHANGS,5-12-2017

•  LTPorNOMSlopemeasurementonlineartraces

•  PhaseshiPinterferometer2Dheightmaps(withfieldsEtching)

LTP

SensiEvity:~50nradAccuracy:± 0.1 – 0.2 µrad

De^lection response is not perfectly linear –  must be calibrated –  can be corrected by measuring the surface

with a series of tilts

SensiEvetothermaldri`–  requiresathermallystabilizedenclosure

(± 0.1 ℃ !!)–  repeatedmeasurementsneededfor

ulEmateaccuracy

HeighterrorscomputedbyintegraEon

PHANGS,5-12-2017

Tuning of a 1m long bender

0 100 200 300 400

-2

-1

0

1

2

3

Slo

pe e

rrors

(µra

d)

(mm)

ESRF SOLEIL

LTP cross-check on a 22 m radius mirror

Phase shift interferometry

Smallfieldrequiredtoreach10mm-1spaEalfrequency⟹S4tchingSensiEvity:~0.1nm=λ/5000Accuracy:±0.3–0.5nm

Usesareferencesurfacewhichisnotperfectlyknown–  mustbecalibrated–  canbeextractedfromasetof

overlappingmeasurementsofagoodflatsurface

SEtchingprocedures–  cannotrelyonreliefcorrelaEon

(smoothsurfaces)–  Mustbeguidedbyother

measurementstoavoidlongrangedistorEonoftheshapewidepupilinterferometer(RADSI)autocollimatororLTPtrace

PHANGS,5-12-2017

SiO2 differential coated mirror

Case study 1 : microfocus 20 KeV

•  Presentstate

•  Source650µmx20µm(HxVFWHM)

–  Transfertosecondarysource inextensionbuilding

•  p=27m,q=58mM=2.1•  Secondarysourceslitcutto40x40µm

fluxloss~40

–  KBdemagnificaEon•  p=83m,q=0.15mM=1/550•  Spotsize~70-100nm

–  Totallength:165m

PHANGS,5-12-2017

•  Upgrade

•  Source15µmx15µm(HxVFWHM)

–  DirectKBdemagnificaEon•  p=40m,q=0.2mM=1/200•  Spotsize~70-100nm

–  Totallength:40m

–  Fitontheexperimentalfloor

–  Shorterlength⟹� beOerthermalstabilitylessvibraEonissues

Case study 2 : VUV beamline

•  Energyrange5-40eV•  Presentstate

–  ElectromagneEc10mlongundulator16periodsof64cm–  CollecEonaperture0.6x0.6mrad2(oversized)–  @5eVK~6.7;Bmax=0.15T–  Totalradiatedpower~500W:incidentpoweronopEcs<100W

•  Upgrade–  Permanentmagnetundulator,4mlong16periodsof25cm–  @5eVK~11;B0=0.47T–  Radiatedpowerdensity~2kW:

needtoreducetheaperturetokeepP<100W

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Case study 3: photoemission beamline ~ 1 keV

PHANGS,5-12-2017

20µm

9m

4m

2m

22m 6.6m 9.4m

2.2m22m 12m

V present

H present

H upgrade

Exitslit5µm 7.4m

WolterrefocL=300mm

2.2m

PGM

30µm

450µm 200µm

20µm

50µm

11µm7µmX6µm

WolterrefocL=70mmRequires slope errors < 0.1 µrad

prefocL=160mm

Conclusion

•  Theclosematchofelectronandundulatordivergence(smallβ)enablesagoodtransferofsourcesizegainstoimagesize

•  Smallersourcesizemeanlessdemagnifica4on–  Morecompactdesign–  SmallerapertureandopEcssize

•  Thissizechangedirectlyaffectstherequirementsonop4csquality–  slopeerrors<0.1µradRMS–  Shapeerrors<1nmRMS–  SynchrotronfaciliEesshoulddevelopthemetrologytocontrolsuch

specificaEons

•  Stabilityrequirementsscaleinthesamepropor4ons–  Thermaldri`–  VibraEons(eginducedbycooling)

PHANGS,5-12-2017