LLNL-CONF-428024

System Modeling of kJ-classPetawatt Lasers at LLNL

M. Y. Shverdin, M. Rushford, M. A. Henesian, C. Boley,C. Haefner, J. E. Heebner, J. K. Crane, C. W. Siders, C.P. Barty

April 16, 2010

ICUIL 2010Watkins Glen, NY, United StatesSeptember 26, 2010 through October 1, 2010

Disclaimer

This document was prepared as an account of work sponsored by an agency of the United States government. Neither the United States government nor Lawrence Livermore National Security, LLC, nor any of their employees makes any warranty, expressed or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise does not necessarily constitute or imply its endorsement, recommendation, or favoring by the United States government or Lawrence Livermore National Security, LLC. The views and opinions of authors expressed herein do not necessarily state or reflect those of the United States government or Lawrence Livermore National Security, LLC, and shall not be used for advertising or product endorsement purposes.

*MiroslavShverdin,shverdin2@llnl.gov,925‐424‐3270PosterPreferred,LLNL-CONF-428024

SystemModelingofkJ­classPetawattLasersatLLNLM.Y.Shverdin*,M.Rushford,M.A.Henesian,C.Boley,C.Haefner,J.E.Heebner,J.K.

Crane,C.W.SidersandC.P.J.BartyLawrenceLivermoreNationalLaboratory

AdvancedRadiographicCapability(ARC)[1]projectattheNationalIgnitionFacility(NIF)[2]isdesignedtoproduceenergetic,ultrafastx‐raysintherangeof70‐100keVforbacklightingNIFtargets.Thechirpedpulseamplification(CPA)lasersystemwilldeliverkilo‐Joulepulsesatanadjustablepulsedurationfrom1psto50ps.Systemcomplexityrequiressophisticatedsimulationandmodelingtoolsfordesign,performanceprediction,andcomprehensionofexperimentalresults.WeprovideabriefoverviewofARC,presentourmainmodelingtools,anddescribeimportantperformancepredictions.

Thelasersystem(Fig.1)consistsofanall‐fiberfrontend,includingchirped‐fiberBragggrating(CFBG)stretchers.Thebeamafterthefinalfiberamplifierissplitintotwoaperturesandspatiallyshaped.Thesplitbeamfirstseedsaregenerativeamplifierandisthenamplifiedinamulti‐passNd:glassamplifier[3].Next,thepreamplifiedchirpedpulseissplitintimeintofouridenticalreplicasandinjectedintooneNIFQuad.AttheoutputoftheNIFbeamline,eachoftheeightamplifiedpulsesiscompressedinanindividual,folded,four‐gratingcompressor.Compressorgratingpairshaveslightlydifferentgroovedensitiestoenablecompactfoldinggeometryandeliminateadjacentbeamcross‐talk.Pulsedurationisadjustablewithasmall,rack‐mountedcompressorinthefront‐end.

Weusenon‐sequentialray‐tracingsoftware,FRED[4]fordesignandlayoutoftheopticalsystem.Currently,ourFREDmodelincludesalloftheopticalcomponentsfromtheoutputofthefiberfrontendtothetargetcenter(Fig.2).CADdesignedopto‐mechanicalcomponentsareimportedintoourFREDmodeltoprovideacompletesystemdescription.Inadditiontoincoherentraytracingandscatteringanalysis,FREDusesGaussianbeamdecompositiontomodelcoherentbeampropagation.Neglectingnonlineareffects,wecanobtainanearlycompletefrequencydomaindescriptionoftheARCbeamatdifferentstagesinthesystem.

Weemploy3DFourierbasedpropagationcodes:MIRO[5],VirtualBeamline(VBL)[6],andPROP[7]fortime‐domainpulseanalysis.Thesecodessimulatenonlineareffects,calculatenearandfarfieldbeamprofiles,andaccountforamplifiergain.Verificationofcorrectsystemset‐upisamajordifficultytousingthesecodes.VBLandPROPpredictionshavebeenextensivelybenchmarkedtoNIFexperiments,andtheverifieddescriptionsofspecificNIFbeamlinesareusedforARC.MIROhastheaddedcapabilityoftreatingbandwidthspecificeffectsofCPA.AsampleMIROmodeloftheNIFbeamlineisshowninFig.3.MIROmodelsarebenchmarkedtoVBLandPROPinthenarrowbandwidthmode.

Developingavarietyofsimulationtoolsallowsustocross‐checkpredictionsofdifferentmodelsandgainconfidenceintheirfidelity.Preliminaryexperiments,currentlyinprogress,areallowingustovalidateandrefineourmodels,andhelpguidefutureexperimentalcampaigns.

Fig.1:OverviewoftheARCsystemhighlightingauniqueversionofCPAarchitecturetoproducetwointensepulsesinoneNIFbeamline.

Mode-locked Fiber

Oscillator ~200 fs

Chirp-fiber- Bragg-

Grating, CFBG

Fiber-splitter

Grating Tweaker A

Grating Tweaker B

ARC fiber front-end

2 independent pulses

Split-beam Injection

(ISP)

MPA PABTS

Main Amps

Combine apertures

Transport switchyard

Dual regens

Amplified split-beam pulse at compressor input

ARC grating Compressor

& input mirrors Parabola & final

optics

2 independent pulses

*MiroslavShverdin,shverdin2@llnl.gov,925‐424‐3270PosterPreferred,LLNL-CONF-428024

Fig.2:FREDmodelofARCsystemprovidesbothasystemleveloverviewandspecificcomponent‐by‐componentdescription.

Fig.3:MIROmodelofARCenablesphysicalopticssystemdescription.ThisworkperformedundertheauspicesoftheU.S.DepartmentofEnergybyLawrenceLivermoreNationalLaboratoryunderContractDE‐AC52‐07NA27344.[1]C.P.J.Barty,et.al.,“AnoverviewofLLNLhighenergyshortpulsetechnologyforadvancedradiographyoflaserfusionexperiments,”Nucl.Fusion,44,S266‐275(2006).[2]C.A.Haynman,etal.,“NationalIgnitionFacilitylaserperformancestatus,”Appl.Opt.46,3276‐3303(2007).[3]R.H.Sawicki,“TheNationalIgnitionFacility:lasersystem,beamlinedesign,andconstruction,”inOpticalEngineeringattheLawrenceLivermoreNationalLaboratoryII:TheNationalIgnitionFacility,Proc.SPIE,5341,43(2004).[4]FREDbyPhotonEngineering,<http://www.photonengr.com/>.[5]OlivierMorice,“Miro:Completemodelingandsoftwareforpulseamplificationandpropagationinhigh‐powerlasersystems,”Opt.Eng.42,1530(2003).[6]J.T.Hunt,K.R.Manes,J.R.Murrayetal.,“LaserdesignbasisfortheNationalIgnitionFacility,”FusionTechnology,26,767‐771(1994).[7]W.H.Williamsetal.,‘‘Opticalpropagationmodeling,’’Proc.SPIE5341,66‐72(2004).

ISP Telescope

TSF

PABST Telescope

CSF Amps 1-11

Injection Optics

Amps 14-18

ISP

OSP

ISP Telescope

TSF

PABST Telescope

CSF Amps 1-11

Injection Optics

Amps 14-18

ISP

OSP