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SearchforX-rayphoton-photonelasticscatteringwithaLaue-casebeamcollider
TomohiroYamajiT.InadaA,T.YamazakiA,T.NambaA,S.Asai,T.KobayashiB,K.TamasakuC,Y.TanakaD,
Y.InubushiE,K.SawadaC,M.YabashiC,T.IshikawaC,T.TakahashiF,S.WatanabeF,G.SatoG
TheUniv.ofTokyo,ICEPPA,KEKB,RIKEN/SPring-8C,Univ.ofHyogoD,JASRIE,ISAS/JAXAF,Univ.ofWasedaG
LNPC’17@yokohama21th,April,2017 1
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Photon-photonscattering
initialphotons
あああああ
virtualelectron
あああああ
あああああああああああああああ
elasticallyscatteredphotons
あああああ
4th-orderQEDprocess
uPhoton-photonscattering・QuantumElectroDynamics(QED)predictselasticscatteringofphotonsinvacuum(1936)=nonlineareffectofvacuum
・Thecontributionofvirtualphotonscatteringisinclusivelyobserved:Delbruckscattering,e/μ anomalousmagneticmoment・Thescatteringofrealphotonshasnoteverbeenobserved→importantverificationofQED
・Ifunknownparticleswhichmediatethescatteringexist,scatteringcrosssectioncanbeenhancedbythepredictionofQED→newphysicsex)Axion LikeParticles(ALP)
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・crosssection(QED)isproportionalto6th powerofphotonenergy
・Allpreviousexperimentsusevisibleorinfraredsources・Thebestupperlimitis18ordersofmagnitude worsethanthepredictionofQED
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Bernard2000
Moulin1996
Hughes1930
crosssectionlog10σ[m2]
1eV 100eV 1MeV10keVvisibleregion
log-logplot
photonenergyωcm@centerofmasssystem
Summaryofpreviousexperiments
1018
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・X rayshave4ordersofmagnitude higherenergythanvisiblephotons→Crosssectionisenhancedby24ordersofmagnitude・X-raydetectorswithhighenergyprecisionimproveS/Nratio・Xrayshavesmallerdiffractionlimit→ beamscanbefocusedmorestrongly・X-rayregion(~10keV)isnewtoparticlephysicsexperiments→interesting!
104
1024
4
Bernard2000
Moulin1996
Hughes1930
crosssectionlog10σ[m2]
1eV 100eV 1MeV10keVvisibleregion X-rayregion
NewexperimentusingX-ray sourcelog-logplot
photonenergyωcm@centerofmasssystem
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・thestrongestX-rayFreeElectronLaser(XFEL)intheworld
◆Specs・pulsedsourcewiththephotonfluxof~6×1011photon/pulse andthedurationof<10fs・beamwidth:200μm(FWHM),and1μmcoherentfocusingisavailable→suitableforscatteringexperimentswithhighluminosity・repetition:30Hz@2015November・X-rayenergy:10.985keVwiththebandwidthof80eV
X-raysource:SACLA
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・X-raydiffractionisusedtosplitX-raybeamsandtomakethemcollideThistechniqueisdevelopedinX-rayinterferometryregion◆X-raybeamcollider・Laue-caseX-raydiffractionatsiliconcrystalisused・Thecolliderconsistsofthreeblades(t0.2mm)manufacturedonasinglemono-crystal
X-raydiffraction@Si(440)
injectedXraystransmitted
Xrays
reflectedXrays
θB
θB
θB
Sithincrystal
thinblades(t0.2mm)
spacing:50mm
beamcollider
X-raycollisionsystem(1/2)
latticeplane
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Gedetector
X-raycollision
50mm
collidervertical(up)direction
monochro Xrays~108 photon/pulse(11keV)
X-raydiffractionacceptablebandwidth:100meV
signalXrays18~20keV
X-raycollisionsystem(2/2)
72°
・ X-raycollisionisspatiallyandtemporallyguaranteedbyageometricalsymmetry・Thepulse-by-pulseintensityofcollidingbeamsaremeasuredbyPINphotodiodes
SACLArawbeam1011photon/pulse
diffractionefficiency:~2%→106 photon/pulse
monochromator80eV→ 60meV
PIN
TR
RR
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・Signalsareveryweakeveniftheyexist→ suppressionofstrayXrays isessential!・TosuppressstrayXraysfromatmosphericmolecules,colliderisinstalledintoavacuumchamber・CollimatorsareinstalledalongtheX-raypathtocutthepathofstrayXraysscatteredbythecollider→ThedetectionrateofstrayXraysisreducedto10-13ofinjectedXrays,andmeasurementwithoutpseudosignalsisachieved!
innerchamber
collider
collimator
Xrays
collisionpoint
experimentalsetup@SACLA
Gedetector
vacuumchamber
goniometer
signalXrays
220mm
SuppressionofstrayXrays:vacuumchamber
Xrays
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Measurementofbeamwidths
PIN
goldenwire
collidingbeam
aportionofbeamisshielded 9
・Beamwidthsismeasuredbyedgescan1)vertical(notfocused):astainlessrod2)horizontal(1μmfocused):φ200μmgoldenwire
・horizontalwidth(σ):0.962±0.037μm(RR)0.992±0.044μm(TR)
verticalwidths:144±12μm(RR)124±7μm(TR)
knife-edgescan
wireposition[μs]
transmittedintensity[arb.]
horizontalscan Theshapeofspectrum=integralofGaussianbeamThetransmittedintensityisfittedbyanerrorfunction
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s]µTiming [1− 0.5− 0 0.5 1
Ener
gy[k
eV]
0
5
10
15
20
25
30
・newestmeasurement(Phys.Lett.B763(2016)454)・measurementperiod:30Hz×~38 hourDAQ=4.1× 106 X-raypulses・timingwindow:detectortimingresolution±5σ=±0.4μs・Nosignificantsignalisobserved
MeasuredX-rayspectrum
MeasuredX-rayspectrum(scatterplot)○:1event
X-raytiming(0:SACLAX-raypulse)[μs]
X-rayEn
ergy[keV
]
NoeventstrayXrays(11keV)
environmentalXrays
◆Potentialsourceofpseudosignals1)pileupsoftwostrayXrays(<22keV)2)accidentalcoincidentofenvironmentalXrays(18~20keV)・pseudosignalsareexpectedto<1event
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・upperlimit(PLB2016)onthecrosssection:1.9× 10-27 [m2]@6.5keV(95%C.L.)
・Thisistheunique/moststringentupperlimitinX-rayregion
Bernard2000
Moulin1996
Hughes1930
photonenergyωcm@centerofmasssystem
cross-sectionlog10σ/m2
1eV 100eV 1MeV10keV
PLB732(2014)356PLB734(2016)454
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visible X-rayregion
Results
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・Theupperlimitis20ordersofmagnitude worsethanQEDprediction・InordertoenhancethesensitivityandapproachtotheQEDprediction,itisessentialtochangetheexperimentalsetupdrastically・Diffractionefficiencyisverysmall(~10-5 ofrawbeam→ 10-10 sensitivityreduction)→Experimentwithoutdiffractionisneeded!
Bernard2000
Moulin1996
Hughes1930
photonenergyωcm@centerofmasssystem
cross-sectionlog10σ/m2
1eV 100eV 1MeV10keV
PLB732(2014)356PLB734(2016)454
~1020
12
visible X-rayregion
Results
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・ExperimentwithoutdiffractionrequiresanadditionalX-raysource・IfanotherSACLAexistsinfrontofSACLA,canphoton-photonscatteringbeobserved?(thoughtexperiment)
・head-oncollisionofX-raypulseswith1012 photon/pulse・50nmfocusing(horizontal/vertical)canbeusedforhead-oncollision→1 photon-photonscatteringper60Hz2dayDAQ
・Inprinciple,X-raycollisioncanbeobservedbyhead-oncollisionof2XFELs→ultimategoalofscatteringexperimentsinX-rayregion
X-raybeams
head-oncollision
dreamplan:SACLA+SACLAhead-oncollision
dreamSACLA
realSACLA
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EH5
◆SACLA+SPring-8head-oncollision・SACLAEH5:simultaneoususageofSACLAandSPring-8BL32Synchronizedoperationwillbedevelopedinthenearfuture→ realisticsetup・SPring-8:~103 photon/pulse,40MHz,40ps(pulseintensityis10-9 ofSACLA)
・Thehead-oncollisionexperimentwith50nmfocusingatEH5→sensitivityenhancementof1011 by60Hz2dayDAQ(109 worsethanQEDprediction)・morerealisticthanSACLA+SACLA:nextstep
realisticsetup:SACLA+SPring-8
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・currentupperlimit:20ordersofmagnitude worsethanQEDprediction
・SACLA+SACLA:QEDpredictioncanbeverified(inprinciple):ultimategoalofphoton-photonscatteringexperimentintheX-rayregion・head-oncollisionofSACLAandSPring-8:sensitivitycanbeenhancedby1011
光子エネルギー
1eV 100eV 1MeV10keV
15
visible X-ray
SACLA×2
SACLA+SPring-8
Summaryofprospectscrosssectionlog10σ[m2]
photonenergyωcm@centerofmasssystem
PLB734(2016)454
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・Weareperformingparticleexperimentsusingphotons・Photon-photonscatteringofrealphotonshasnoteverbeenobserved:importantverificationofQED・WehaveperformedfirstscatteringexperimentinX-rayregion・X-raydiffractionisusedtosplitXraysandmakethemcollide・BackgroundXraysaresuppressedtoperform0-pileupexperiment・Theupperlimitoncrosssectionis1020 worsethanQEDprediction:drasticchangeofexperimentalsetupisnecessary
・SACLA+SACLA:sensitivitycanapproachtoQEDpredictioninprinciple:ultimategoalofX-rayphoton-photonscatteringexperiment・head–oncollisionofSACLAandSPring-8:sensitivityisenhancedby1011:nextstep
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Summary