High Brightness Electron Beam Diagnostics and their ... - CASA

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theendofthemagneticdecompressorisbestdescribedintermsofsequencesofparmelaruns response.Theevolutionofthelongitudinalphasespacefromtheelectronbunchemissionupto showningure5.1.Inthefollowingweonlyconcentrateonthecaseof60pCchargeperbunch withlasingturnedo. 2.Therstelementthatsignicantlyaectsthelongitudinalbunchdistributionisthebuncher 1.Thelengthoftheelectronbunchafteremissionviaphotoelectriceectandaccelerationto cavity.Thiscavityisoperatedatzero-crossingsothattheaveragearrivaltimeofthebunch coincideswithazeroacceleratingeld.Theelectronsarrivingsooner(i.e.thatbelongtothe bunchhead)aredeceleratedwhereasthelateelectrons(i.e.thatarelocatedinbunchtail)are accelerated(seeFig.5.1(B)).Hencetheprincipaleectofthiscavityistoprovideanenergy rampacrossthebunch.Thisenergymodulationtranslatesasthebunchpropagatesthough 350keVintheDC-gunstructureisapproximately15ps(RMS)(seeFig.5.1(A)). 3.Afterdriftingthroughalongitudinallyfreespace,thebunchenterstherstaccelerating adriftspacetoa\bunching"oftheelectrons:becauseoftheelectrons'averageenergyof ofappropriatelengthwillbunchtheelectrons(mathematicallythistraducestothenonzero approximately350keV,whichmakethemnonrelativistic,theirpropagationinadriftspace valueofthemomentumcompactionofadriftspaceoflengthL:R56=L=2). 4.Approximately7cmaftertheexitofthepreviouscavity,thebunchentersasecondSRF- constantuptothecavityexitwhiletherelativeenergyspreadisgreatlyreduced. ofthecavity(thatactsasacapturesection),thenthebunchlengthisfrozenandremains acceleratingelectriceld).Thereisastrongcompressionoccurringinthersttwocells Thecavityisoperatedformaximumenergygain(whichdoesnotmean,becauseofthenonrelativisticnatureoftheelectron,thatthebunchisinjectedinphasewiththemaximum ve-cellCEBAF-typeSRF-cavitywithanominalaverageacceleratinggradientof11MV=m. themaximumenergygainphase,sothatitprovidesfurtherbunchcompression.Indeedthe choiceofthephaseismadetoimpressthelongitudinalphasespacewiththeproperslope cavitywithanominalaverageacceleratinggradientof9MV=m.Thiscavityisoperatedo neededtomatchtheslopedesiredattheentranceoftheupstreamachromaticchicanefor optimumbunchingthroughthischicane.Atthecavityexit,theparametersare:1.2psfor 6.ThenthebunchisinjectedintheSRFlinac.Thegradientofeachcavityandtheoverallphase 5.Theelectronsthendriftthroughanachromaticthree-bendchicane.Thislattercanreduce thebunchlengthbymeansofmagneticcompressionthatisbasedonthefactthatpathlength insidebendsisenergydependent. thebunchlength,4%fortherelativeenergyspreadandapproximately10MeVforthebeam ofthelinacisadjustedtogivepreciselythedesiredenergy(whichwilldeterminetheFEL averageenergy. 7.Thecompressorchicanewillcompressthebunchdownto120m(RMS)toachievethe 8.Afterthewigglerasecondchicanethatactsasadecompressorchicanelengthensthebunch chicane. minimumbunchlengthatthewigglerlocation. wavelength)andtoadjusttheincomingbunchlengthandenergyspreadinthecompressor length.

concentrateonthebeamparametersintheundulatorvicinity,whichareofimportancetostartup oftheFELprocessandquantifyfewofitsproperties. Thebeamdynamicsintherecirculationwillbedescribedlater.Inthepresentchapterweonly 9.Thebeamisthenrecirculated. E (keV) . . . . . . . . . .. . . ... .. . . . .. . . . . .. .. . . .. . . . . . . . . . . . .. . . .. . . . . ... . .. . .. .. . . .. . . . .. .. . .. .. . . . . ... .. . .... ... . . .. . .. . ... .. . . .. . . . . . .. . .. . .. . .. .. . . .. . . . . .. . .. . . .. . . .. . .. . . . . . ... ... . .. . . .... .. .. . . . . .. . . . .. .. . . . . .. . .. . . . .. . .. . . . ... . . . . . .. . . . . . . . . . . ... . .. . . . . . . . . .. . . ... . . . . . .. . . .. . .. . . . ... . . .. .. .. . . . . .. . . .. . . . .. . .. . . 5 4 3 2 1 0 .. .. ... .. . . . .. . . . . ... . -1 -2 -3 -4 -5 -30 -15 0 15 30 . . .. . . . . . . . . . . .. . . . .... . .. . .. .. ... .. .. . . . ... . . . ... .. . . ... . . . . . .... . ... .. . . ... . .. ..... . ... . . .. . . .. . . .. ... . . . . . .. . .. . . . .. .. . .. . .. ..... .. ... . .. .. . . . .. . . .. . .. . .. .. . . . .. . .. . . . . . .. . .. . .. . . ... . . . . . .. . . . .. . . .... .. ... ..... .. . .. . . .. . . . .. . . . . .. .. . .. . . . ... . .. ..... .. . . . . ... . .. . . . . . . . . .. .. . . ... . ..... . . . . ... .. .. .... . ... . . .. . . . .... .. . .. .. . .. .... . . . . .. . .. . . .. . . .. .. . .... . . . . . .. . . . . . . . 20 .. . ... . 15 10 5 0 -5 -10 -15 -20 -30 -15 0 15 30 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . 20 15 . 10 . . . . . . . 5 . . . . . . . . . . . 0 . . . . . . . . . . ... . . . . . . -5 . . . . . . -10 -15 -20 -5.0 -2.5 0.0 2.5 5.0 .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . .. . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . .. . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . 100 80 60 . . 40 . . . . . 20 . . . . . . . . . 0 . . .. . . . .. . ... . -20 . . . . . . -40 . -60 -80 -100 -5.0 -2.5 0.0 2.5 5.0 .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ... . . . . . . . .. . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 100 . 80 . 60 . . . 40 . . 20 . 0 . . . . . . . . . . -20 . . . . . . -40 . . . . . . . -60 . . -80 -100 -5.0 -2.5 0.0 2.5 5.0 . . . . . . . .. . . . . . .. . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . .. . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 100 80 60 40 20 0 -20 -40 -60 -80 -100 -5.0 -2.5 0.0 2.5 5.0 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . .. . . . . . . . . .. . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . 100 . 80 . . . . . . .. . 60 . . . . . . . . 40 . . 20 . . . . 0 . . . . . . -20 . . -40 -60 -80 -100 -5.0 -2.5 0.0 2.5 5.0 (RF-deg.) . . . . . . . . . . . . . . . . . . . . . . . ... . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . .. . . . . . . . . . .. . . . . . . . . . . . . . .. . . . . . . . . . .. . . . . . .. . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . .. . . . . . . .. . . . . . . 100 80 60 40 20 0 -20 . -40 . . . . -60 . -80 -100 -5.0 -2.5 0.0 2.5 5.0 (RF-deg.) . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . .. . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . .. . . . . . . . . (D) (E) (F) longitudinalphasespaceisplottedattheexitofthegun(A),thebuncher(B),theSRF-cavity#1 (C),theSRF-cavity#2(D),theachromaticchicane(E),theSRF-linac(F),thebunchcompressor chicane(G),thebunchdecompressorchicane(H),thearc#1(I).Notethatelectronswithpositive Figure5.1:SequencesofparmelarunsdemonstratingthebunchingprocessintheIRFEL.The 100 80 . . (G) (H) 60 (I) 40 20 0 -20 -40 -60 -80 -100 -10 -5 0 5 10 WepresentedinChapter2theformalismassociatedtotheemissionofelectromagneticwaves 5.3TheoryofBunchLengthMeasurementusingFrequencyDomain belongtothebunchtailwhiletheonewithnegativeareinthebunchhead. (RF-deg.) possiblefromthelattertoextractinformationonthelongitudinalbunchdistribution. namedthespatialandangularBFF.InthenextsectionwestudybothBFFsandshowhowitis (d2P=(d!d))bysuchsystemhasacontributionthatisproportionaltoN2,whereNisthe byamulti-particledistribution.Wehaveseenthatthetotalspectralangularpoweremitted calledbunchformfactor(BFF)f(!;bn)thatinturncanbewrittenastheproductoftwofactors numberofelectronsinthemulti-particlesystem.Thiscontributionisalsoproportionaltotheso E (keV) E (keV) (A) (B) (C)

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Page 44 and 45: Study TheFELdriveraccelerator:Latti

Page 46 and 47: ParameterValue x -0.178 x(m) 8.331

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Page 52 and 53: etatronexcitationaspicturedingure3.

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Page 78 and 79: and validundertheassumptionofaunifo

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Page 86 and 87: Actuator Inserts Foil and Mirror CI

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