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
PHANGS,5-12-2017
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
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