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Self-similarelectronbeam:prospects,demands,andapplications
28September,2018 Channeling 2018 1
A.Aryshev1,D.Yu.Sergeeva2,3,M.Shevelev4,L.G.Sukhikh4,A.A.Tishchenko2,3,N.Terunuma1 AndJ.Urakawa1.
1 KEK:HighEnergyAcceleratorResearchOrganization,1-1Oho,Tsukuba,Ibaraki305-0801,Japan.2 NationalResearchNuclearUniversity(Mephi),Kashirskoe Shosse 31,Moscow,115409,Russia.3 NationalResearchCenter“Kurchatov Institute”,Akademika Kurchatova Pl.1,Moscow,123098,Russia4 TomskPolytechnicUniversity,LeninAvenue30,Tomsk634050,Russia
Outline• Generalmotivation
• Pre-bunchedTHzFELandpre-bunchedbeameffectontopolarizationradiations.
• Presentexperienceoflongitudinalandtransversee-beamshapinginRFguns.
• Aconceptofself-similarbeams.• LUCXfacility.• Fractalbeamgeneration.• Michelsoninterferometerasadirecttime-domainanalyzer.
• Conclusionandsummary.
28September,2018 Channeling 2018 2
Motivation• Constructionofastableandtunablelasersystemfor
RFgundevelopmentandTHzradiationsourcestestsbasedonmoderntechnology.
• Buildabroadcollaborativenetworkamongleadinginstitutionsworldwide.
• Developstate-of-the-arttunablecoherentTHzradiationsourcesonthebasisofacompact(preferablytable-top)accelerator.
28September,2018 Channeling 2018 3
MASAYOSHI TONOUCHIInstitute of Laser Engineering, Osaka University, Japan
AGTaX collaborationnetwork
28September,2018 Channeling 2018 4
Fig. 1 Synchrotron radiation emitted by a bending magnet
The properties of Coherent Radiation
( ) ])/(4exp[2exp2
exp21, 2
2
2
2
2λπσ
λπ
σπσλσ z
zz
z dzzizF −=⎟⎠
⎞⎜⎝
⎛ ⋅⋅⋅⎟⎟⎠
⎞⎜⎜⎝
⎛
⋅
−⋅= ∫
∞
∞−
( )[ ]−Ω
⋅+≈Ω egle
z ddPdFNN
ddPd
sin
22
2
,ω
λσω
Gaussian distribution of electrons within the bunch
Synchrotron radiation
Form-factor:
ü Extreme sensitivity to the radiative bunch length*ü Form-factor “cut-off” becomes effective when the
rms bunch length becomes longer than ~ λ/2
single electron spectrum
Transition radiation
22
( ) exp sin zkf k k ρ
σσ θ
β
⎡ ⎤⎛ ⎞⎡ ⎤⎢ ⎥⎡ ⎤= −⎜ + ⎟⎢ ⎥⎣ ⎦⎜ ⎟⎢ ⎥⎣ ⎦⎝ ⎠⎣ ⎦
Where k – wave number, θ – observation angle, β - the velocity of electron in the units of speed of light
2 2
2 2
1 ( )( , ) exp2 2
x yg x yρ ρπσ σ
⎡ ⎤+= −⎢ ⎥
⎢ ⎥⎣ ⎦
2
2
1( ) exp22 zz
zh zσπσ
⎡ ⎤= −⎢ ⎥
⎣ ⎦
Coherentformfactordependentson:ü angleofobservation.ü transversesizeofbunch.ü longitudinalsizeofbunch.
Bunchedbeamcase
28September,2018 Channeling 2018 5
Compactpre-bunched generationschemesProf.Y.-C.Huang,NationalTsinghuaUniversity,Hsinchu,Taiwan
ShengguangLiu,Yen-Chieh Huang,NIMA637(2011)S172–S176
28September,2018 Channeling 2018 6
@2THz(150um),timespacingbetweenlaserpulsesis500fs.16-pulsetrainof50fs.Pulsetrainchargemorethan200pC,photocathodeQ.E.1%.Peakpoweratmegawatt(MW)level,0.1mJ
LLNL:linac-driven,laser-basedComptonscatteringgamma-raysource
28September,2018 Channeling 2018 7
T~87ps
R.A.Marshetal.,“ModelingandDesignofanX-BandRFPhotoinjector”,Phys.Rev.STAccel.Beams,vol.15,p.102001,2012.
Gibson,D.,Hwang,Y.andMarsh,R.,2017,May.InitialPerformanceMeasurementsofMulti-GHzElectronBunchTrains.In 8thInt.ParticleAcceleratorConf.(IPAC'17),Copenhagen,Denmark,14â19May,2017 (pp.795-797).JACOW,Geneva,Switzerland.
UV e-beam
100pC
OTR?SR?
RFGunlaser
Interference-relatedmethods
28September,2018 Channeling 2018 8
Neumann,J.G.,Fiorito,R.B.,O’Shea,P.G.,Loos,H.,Sheehy,B.,Shen,Y.,&Wu,Z.(2009),Terahertzlasermodulationofelectronbeams.JournalofAppliedPhysics,105(5),053304.
Shen,Y.,Yang,X.,Carr,G.L.,Hidaka,Y.,Murphy,J.B.,&Wang,X.(2011).Tunablefew-cycleandmulticyclecoherentterahertzradiationfromrelativisticelectrons.Physicalreviewletters, 107(20),204801.
Birefringentcrystalarray
28September,2018 Channeling 2018 9
Dromey,B.,Zepf,M.,Landreman,M.,O'keeffe,K.,Robinson,T.,&Hooker,S.M.(2007).Generationofatrainofultrashortpulsesfromacompactbirefringentcrystalarray. Appliedoptics,46(22),5142-5146.
Giorgianni,F.,Anania,M.P.,Bellaveglia,M.,Biagioni,A.,Chiadroni,E.,Cianchi,A.,Daniele,M.,DelFranco,M.,DiGiovenale,D.,DiPirro,G.andFerrario,M.,2016.TailoringofhighlyintenseTHzradiationthroughhighbrightnesselectronbeamslongitudinalmanipulation.AppliedSciences,6(2),p.56.
Yan,L.,Du,Q.,Du,Y.,Hua,J.,Huang,W.andTang,C.,2011.UVpulseshapingforthephotocathodeRFgun.NuclearInstrumentsandMethodsinPhysicsResearchSectionA:Accelerators,Spectrometers,DetectorsandAssociatedEquipment,637(1),pp.S127-S129.
28September,2018 Channeling 2018 10
Typicallaserpulseparameter requirements forRFgunphotocathode• Pulseenergy,>10uJforCs2Te• Pulseduration,~100fs–10ps
• Space-chargelimited• Wavelength,~250nm forCs2Te
• Hence,HighHarmonicGenerationisneeded• Conversionefficiencydependsonpulsedurationandharmonic
• Pulserepetitionrate• Hz(machine),MHz(multi-bunch),GHz-THz(micro-bunch)
• Timingstability,<1ps (~1deg.RFphase(2.8GHz))• Stabilizedandsynchronizedoscillator• StabilizedLaserTransportLine
• Pointingstability,smallerthanrms spotsize,typ <100um.• StabilizedLaserTransportLine• Additionalspatialfilters
• Spatialandtemporalpulseshaping• Pulsestacking• Micro-lensarrays• π-shapers
28September,2018 Channeling 2018 11
RFGunlasersystemtechnologies
28September,2018 Channeling 2018 12
• Solid-state-basedtechnology • Fiber-basedtechnology
Ti:Sa
Yb-dopped fiberforexample
courtesyY.HondaA.Chong, W.H.Renninger, F.W.Wise,Opt. Lett. 33(2008)2638:NumericalsimulationsofYb-dopedfiberlasersindicatethat~30fspulsesarepossibleforarealisticdesignwithoff-the-shelfcomponents.Experimentsareconstrainedbytheavailablepumppower,but~75fspulsesareobtained.(justforoscillator!!!)
Er-dopedfiberlaserisalsopromisingcandidate
Nd:YAG
Hzrep.ratefspulseHighEnergyComplexity
Hzrep.rateps pulseHighEnergySimplisity
MHzrep.rate~100fspulseLowEnergySimplisity
What’ssoSpecialAboutps-fsLasers?
Shortopticalpulse.• Mostofenergydissipationandtransferprocessesoccuronthetimescalelargerthan100fs.
• Femtosecondlaserpulsesenableonetogenerateelectronbuncheswithsimilardurations(stronglyrelatedtogenerationofTHzradiation).
• Specificlasersystemdesignapproaches.
• SpecificgainmaterialsduetoopticalBWandefficiencywithfspulses.
• Specificpulsediagnostics.
Highpeakpowerofthelight• I~J/Tpulse,I– Power,J– pulseenergy.
• 1mJ pulsewith10nsduration- 0.1MW.• 1mJ pulsewith100fsduration- 10GW.
• Non-linearresponseoftheopticalcomponents(e.g.,multi-photonabsorption,opticalharmonicsgeneration,materialsablation,etc.)
Largebandwidth• Broadbandopticalcomponents(mirrors,etc)
• Achromaticlens,waveplates,etc.• Higherdemandsforlasersafety.
28September,2018 Channeling 2018 13
W.Kaiser,ed.,“UltrashortLaserPulses:GenerationandApplications”,Springer-Verlag,Berlin,1993
Multi-micro-bunchbunches(self-similaror“Fractalbeam”.)
28September,2018 Channeling 2018 14
4micro-bunches1multi-bunch(1RFbucket)
4micro-bunches4multi-bunch(4RFbuckets)
• DAQseesthismicro-trainasasingleevent(notriggermodificationisrequired)
• Micro-bunchspacingchangingsimultaneouslyinallbuckets
3.13Hz(machinerep.rate)
RF,2856MHz(bucketperiod~350ps)
0.1- 3THz(variable)
RF,2856MHz
2.8GHz
• NumberoffilledRFbucketsdependsonlyonFHlaserenergybudget
• Non-sequentialRFbucketfillingispossible
• OneofthetypicalS-bandacceleratorparameters:• Multi-bunchrep.rate (fromtheRFgunlaseroscillator)~357MHz(every9th RFbucket)• RFpulsewidth~4us=>max1400bunches(roughly)– fillingtimeetc.~1250bunches
• Applying8-timespulsesplit->10000bunches/4us!!!• Effectson:X-rayCompton,Fiberlaseroscillatorsimplementation,totalradiatedpower.
Pulsesplitter
28September,2018 Channeling 2018 15
• C.W.Sidersetal.,“EfficientHigh-EnergyPulse-TrainGenerationusinga2n-PulseMichelsonInterferometer”,Appl.Opt.,vol.37,p.5302,1998.
• Liu,S.andHuang,Y.C.,2011.Generationofpre-bunchedelectronbeamsinphotocathodeRFgunforTHz-FELsuperradiation.NIMA,637(1),pp.S172-S176.
• Theseapproachesgivealternativepolarizationswithinthetrain.
• Whatisleadingtoatleast50%losesondownstreampolarization-sensitivelasercomponents(Amplifiers,Compressors,HHG,etc.)
l/2l/4
l/4 “Delay”
“Buncher”,second(current)prototype
28September,2018 Channeling 2018 16
Generalshemeof16-buncherPhotoofpre-assembledbuncher
§ AllbitsweredeliveredinSeptember2014.§ Assembledandtested(lasersideonly)inNov.-Dec.2014§ Tested(e-beamgeneration)inJan.– Feb.2015
Laser pulse splitter (buncher)
Channeling 2018 17
Micro-bunchesMulti-bunches
28September,2018
LUCX Facility
28 September, 2018 Channeling 2018 18
FSTB
Nd:YAG
Modulator #0
KLY#0
LUCX accelerator tunnel
KLY#1
Modulator #1LUCX control room
Ti:Sa laser system (FSTB)
1928 September, 2018 Channeling 2018
Operational parameters Original 4 years later
Repetition rate, max 10Hz 3.13Hz
Central wavelength 795nm 795nm
Pulse energy before compression 22mJ 5mJ
Pulse energy after compression 14mJ 3mJ
Pulse duration w/w-o correction 30/37.7fs 50fs
Energy stability 22mJ@800nm 1.6% 3%
• Entire infrastructure was built• Control soft 80% re-written• Additional pulse diagnostics introduced• THG simulated, ordered, built• 2 buncher systems were implemented
Multi-micro-bunch,implementation
Channeling 2018 20
Presentcondition:4x4pulses,~50fseach,convertedto266nm,10uJ
• Totalsplittingefficiency~20%• Newdesignwithtotal10-20%losesispossible.• Beamexpanderwasremoved.• Multi-passAmp,Compressor,THG,LTLre-
tuned.• Micro-bunch
– Separation:+/- 5ps– Stability:<20fs(lowerthanmeas.resolution)
• Multi-bunch– Separation:350ps+/- 30ps ManualdelaycontrolMotorizeddelaycontrol
28September,2018
FSTB:fs SingleShotcross-correlator
28September,2018 Channeling 2018 21
ThemethodbasedontheregistrationofcrossdistributionofSecondHarmonic(SH)energyproducedinnonlinearcrystalundernon-collinearinteractionoftwobeamswithdeterminedaperture.
SHGCrystal
CameraA
BC
C
A
B
4-microbunchgeneration
28September,2018
“zero-cross”“Kly1off”
YAGYAG
Channeling 2018 22
A.Aryshev,M.Shevelev,Y.Honda,N.Terunuma,J.Urakawa,FemtosecondresponsetimemeasurementsofaCs2Tephotocathode,Appl.Phys.Lett.111,033508(2017).
MeasuredCs2Tephotocathodepeak-to-peakresponsetime369.48± 27fs.
Tunability
28September,2018 Channeling 2018 23
Amplitudemodulation
“phase”modulation
“phase”modulation
M.Shevelev,A.Aryshev,N.Terunuma,andJ.Urakawa,“Generationofafemtosecondelectronmicrobunch trainfromaphotocathodeusingtwofoldMichelsoninterferometer”,Phys.Rev.Accel.Beams 20,103401(2017).
4-multibunchgeneration
Channeling 2018
Tek TDC684B,1GHz,5Gs/s Tek DPO7354,5GHz,40Gs/s
500ps/div
FCT Scope
30mRFcable
500ps/div
FCT Scope
1mRFcable
4bunch 2bunch
Everysecondbucket(~700ps)
28September,2018 24
Space-chargeforcesuppression
28September,2018 Channeling 2018 25
l.Serafini,et.al.NIMA387(1997)305-314 ASTRAsimulation,LUCXRFgun
• Accelerationgradient,up->limitedbydischarge• Charge,down->limitedbydetector’ssensitivity• UVspotsize,up->limitedbyoff-axisdynamics• UVPulselength,!!!->limitedbyTHG• Multi-bunch->limitedonlybybeam-loading
M.Shevelev, A.Aryshev, Y.Honda, N.Terunuma, J.Urakawa,Influence ofspacechargeeffectinfemtosecond electron bunch oncoherent transitionradiationspectrum, Nucl. Instrum. Methods Phys.Res.,Sec.B402,134(2017).
Numberofmicro-bunches/RFbucket?
28September,2018 Channeling 2018 26
Parametersthatwillbenaturallydifferentforeverymicro-bunch:
• Charge(pow(N,2)dependence)• E,dE (Lineardependence)• Sigma_z (exponentialdependence)• Sigma_x,y (dependsonradiationtype)
16micro-bunchASTRAsimulation
courtesyS.Liu
Numberofmicro-bunches/RFbucket(workinprogress)
28September,2018 Channeling 2018 27
• Amplitudes(charge)• Functiononphase
Longitudinalform-factor
28September,2018 Channeling 2018 28
0 2 4 6 8 10 12
0
1000
2000
3000
4000
5000
6000
-0.05 0.00 0.05 0.10 0.15 0.20
0
1000
2000
3000
4000
5000
6000
Char
ge, fC
Longitudinal coordinates, m
Char
ge, fC
Longitudinal coordinates, m0 1000 2000 3000 4000 5000
-5
0
5
10
15
20
25
30
35
40
Ampli
tude
Frequency, GHz
0 2 4 6 8 10 12
0
1000
2000
3000
4000
5000
6000
-0.02 0.00 0.02 0.04 0.06 0.08 0.10 0.12 0.14
0
1000
2000
3000
4000
5000
6000
Char
ge, fC
Longitudinal coordinates, m
Char
ge, fC
Longitudinal coordinates, m0 1000 2000 3000 4000 5000
-20
0
20
40
60
80
100
120
140
160
180
200
Ampli
tude
Frequency, GHz
100single,260fsbunchesat2.8GHz
100x16,260fs,2.2THzbunchesat2.8GHz
Michelsoninterferometerasadirecttime-domainanalyzer
28September,2018 Channeling 2018 29
-100 -50 0 50 100-1.5
-1.0
-0.5
0.0
0.5
-4 -2 0 2 4-1.5
-1.0
-0.5
0.0
0.5
Nor
mal
ized
inte
nsity
, arb
. uni
ts
Optical path difference (mm)
Nor
mal
ized
inte
nsity
, arb
. uni
ts
Optical path difference (mm)
250 300 350 400 450 500 550 600 650 700
0.000
0.002
0.004
0.006
0.008
Am
plitu
de
Frequency, GHz
-100 -50 0 50 100-1.4
-1.2
-1.0
-0.8
-0.6
-0.4
-0.2
0.0
0.2
0.4
0.6
0.8
Nor
mal
ized
inte
nsity
, arb
. uni
ts
Optical path difference (mm)
300 350 400 450 500 550 600 650 700
0.000
0.005
0.010
0.015
Am
plitu
de
Frequency, GHz
CTR– broadbandspectrumSBD– narrowbandsensitivitySBDspeed<<bunchseparation
FToftworadiationpulsesgivesdiscretespectralineswhereaseachpulsehasbroadspectrum!!!
Pulseseparation>>radiationpulseduration
Michelsoninterferometerasadirecttime-domainanalyzer
28September,2018 Channeling 2018 30
-600 -400 -200 0 200 400 600-100
-50
0
50
100
150
200
250
300
350
400
-30 -20 -10 0 10 20 30
-50
0
50
100
150
200
250
300
350
Nor
mal
ized
inte
nsity
, arb
. uni
ts
Optical path difference (mm)
Norm
alize
d in
tens
ity, a
rb. u
nits
Optical path difference (mm)0 200 400 600 800 1000
0.10
0.15
0.20
0.25
0.30
0.35
0.40
0.45
0.50
0.55
Ampl
itude
Frequency, GHz
-600 -400 -200 0 200 400 600-100
0
100
200
300
400
-60 -40 -20 0 20 40 60-100
0
100
200
300
400
Norm
alize
d int
ensit
y, ar
b. u
nits
Optical path difference (mm)
Norm
alize
d in
tens
ity, a
rb. u
nits
Optical path difference (mm)0 200 400 600 800 1000
0.0
0.2
0.4
0.6
0.8
1.0
Ampl
itude
Frequency, GHz
Pulseseparation>>radiationpulseduration
Conclusion&Summary• Followingelectronbeamparametersweconfirmed:
• Energy~8.5MeV• Energyspread<1%rms• Transversermsbeamsize@THzstation~500x500um• Bunchlength~360 fs peak-to-peak (4micro-bunchaverage)• Numberofmicro-bunches– 4• Minimummicro-bunchtimeseparation~0 fs• Micro-traincharge(4 micro-bunches)~0- 200pC• Bunchrep.rate THz+GHz+Hz wasconfirmed.AdditionofMHzrep.rate require
constructionofthefiberlasersystem.
28September,2018 Channeling 2018 31
Conclusion&Summary
• Anewconceptofself-similar(fractal)beamisintroduced.• DirectutilizationofTHz+GHz e-beamisobviousforUR,cSPR,ChR.• CareshouldbetakenwithshortpulseprocesseslikeCTRandCDR.• MHzrepetitionandassociatedradiationpulsescanbetrappedinthe
enhancementcavity.• Michelsoninterferometercanbeconsideredasapowerfultoolfora
directtime-domainmeasurements.• Detectortimeresponseplaysanimportantrole.• Acareshouldbemadeindeterminationofthesuper-radiantradiation
spectralcharacteristics.• Nearfuturedemandsinclude:
• Effectivelongitudinaldiagnostics(bothlaserpulsesande-beam).• Theoreticalextensiontoaccountforrealisticbeamparameters.
28September,2018 Channeling 2018 32
Thankyouforyourattention
28September,2018 Channeling 2018 33
Materials• Jean-ClaudeDiels,WolfgangRudolph:“Ultrashortlaserpulsephenomena”,Secondedition,2006
• ToneRotar,“Ultrashortlaserpulses”,Ms Thesis.• CarloAntoncini,“UltrashortLaserPulses”,Lecturenotes.• YuelinLi,ANL,2008USPAS,summersessionlecturenotes.• Valerii (Vartan)Ter-Mikirtychev,“FundamentalsofFiberLasersandFiberAmplifiers”,Springer,2014
• YanYOU,“Yb-dopedMode-lockedfiberlaserbasedonNLPR”,2012• AlexanderMikhailovsky,“Basicsoffemtosecondlaserspectroscopy”
• JeremyR.Gulley,“SimulationofUltrashortLaserPulsePropagationandPlasmaGenerationinNonlinearMedia”.
• S.LIetal.PHYS.REV.ACCEL.BEAMS20,080704(2017)• H.Tomizawa,“Adaptiveaptive3D-LaserpulseshapingSystemtoMinimizeEmittanceforPhotocathodeRFgun”,WEBAU01,FEL2007
28September,2018 Channeling 2018 34
Miro-bunchtraincharacterizationToprow:typicalelectrondensitydistributionsfordifferentBH1Gcurrent.
Bottom:beamimagecentroidpositionvselectronbeamenergy(reddots)withlinearfit:
amplitude7.2± 0.02MeV
andslope−2.65·10−2 ± 1.16·10−3 MeV/mm
BeamimagecentroidpositionvsRFphase(bluedots)withlinearfit:slope0.102± 7.3·10−3 deg./mm
Typicalelectrondensitydistributionmeasuredfor(a):−0.25deg.,(b):0deg.,(c):0.25deg.acceleratingphase;
(d- i):Typicaltwomicro–bunchelectrondensitydistributionmeasuredfor0deg.acceleratingphaseand(d):4.8mm,(e):4.815mm,(f):4.825mm,(g):4.850mm,(h):4.865mm,(i):4.875mmrelativeM2mirrorpositions.
28September,2018 Channeling 2018 35
4-microbunchgeneration
28September,2018 Channeling 2018 36
“zero-cross”“Kly1off”
• YAGscreenshowsgreaterperformanceoverDMQ• Analysisshouldbeimproved• Beamdynamicsandcoherentradiationstudies
alreadycanbeperformed
DMQ
YAGYAG
Initialtwomicrobunchobservation
28September,2018 Channeling 201837
Ballistice-optics,Klystron1off
EnergyBendarm
StraightarmTimediff.14.58ps
Estraight =8.70± 0.003MeVdEstraight =165.0±5.02keVEbend =8.34± 0.003MeVdEbend =66.08±2.51keVEdiff =360± 4.2keV
SetRFphaseforboth320deg.Actualacceleratingphase:20deg.– bendarm35deg.– straightarm
MeasuredathighchargeduetolimitedICTsensitivity
Setp
hase
MS3G
25/07/2014
RFzero-crossing
28September,2018 Channeling 2018 38
KEK-TPU,Super-radiantradiationemissionstudy.
CDR cSPR ASTRA
1bunch Int scanvsRFgunφ,3points Int scanvsRFgunφ,3points
ü
2bunch M2scanslowandhighQ - -
4bunch • M1scanlowandhighQ• FSTBatt scan• Int scanvsRFgunφ, 6
points
• -• -• Int scanvsRF
gunφ,3pointsü 6 points
28September,2018 Channeling 2018 39
Summaryof2016.12.06study
1bunch
cSPR
4bunch 4bunch 4bunch
CDR,super-radiantemission
28September,2018 Channeling 2018 40
1bunch
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