self-similar electron beam: prospects, demands, …self-similar electron beam: prospects, demands,...

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.


Motivation• Constructionofastableandtunablelasersystemfor

RFgundevelopmentandTHzradiationsourcestestsbasedonmoderntechnology.

• Buildabroadcollaborativenetworkamongleadinginstitutionsworldwide.

• Developstate-of-the-arttunablecoherentTHzradiationsourcesonthebasisofacompact(preferablytable-top)accelerator.


MASAYOSHI TONOUCHIInstitute of Laser Engineering, Osaka University, Japan

AGTaX collaborationnetwork


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


Compactpre-bunched generationschemesProf.Y.-C.Huang,NationalTsinghuaUniversity,Hsinchu,Taiwan

ShengguangLiu,Yen-Chieh Huang,NIMA637(2011)S172–S176


@2THz(150um),timespacingbetweenlaserpulsesis500fs.16-pulsetrainof50fs.Pulsetrainchargemorethan200pC,photocathodeQ.E.1%.Peakpoweratmegawatt(MW)level,0.1mJ

LLNL:linac-driven,laser-basedComptonscatteringgamma-raysource


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


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


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.

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


RFGunlasersystemtechnologies


• 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.


W.Kaiser,ed.,“UltrashortLaserPulses:GenerationandApplications”,Springer-Verlag,Berlin,1993

Multi-micro-bunchbunches(self-similaror“Fractalbeam”.)


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


• 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


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


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


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


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?


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)


• Amplitudes(charge)• Functiononphase

Longitudinalform-factor


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


-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


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


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


-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


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


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.


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.


Thankyouforyourattention


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


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.


4-microbunchgeneration


“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


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


Summaryof2016.12.06study

1bunch

cSPR

4bunch 4bunch 4bunch

CDR,super-radiantemission


1bunch

self-similar electron beam: prospects, demands, …self-similar electron beam: prospects, demands,...

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