简介:Anionbeamhastheuniquefeatureofbeingabletodeposititsmainenergyinsideahumanbodytokillcancercellsorinsidematerial.However,conventionalionacceleratorstendtobehugeinsizeandcost.Inthispaper,afutureintenselaserionacceleratorisdiscussedtomakethelaser-basedionacceleratorcompactandcontrollable.Theissuesinthelaserionacceleratorincludetheenergyefficiencyfromthelasertotheions,theionbeamcollimation,theionenergyspectrumcontrol,theionbeambunching,andtheionparticleenergycontrol.Inthestudy,eachcomponentisdesignedtocontroltheionbeamqualitybyparticlesimulations.Theenergyefficiencyfromthelasertoionsisimprovedbyusingasolidtargetwithafinesub-wavelengthstructureoranear-critical-densitygasplasma.Theionbeamcollimationisperformedbyholesbehindthesolidtargetoramulti-layeredsolidtarget.Thecontroloftheionenergyspectrumandtheionparticleenergy,andtheionbeambunchingaresuccessfullyrealizedbyamulti-stagelaser–targetinteraction.
简介:Ashortoverviewofthetheoryofaccelerationofthinfoilsdrivenbytheradiationpressureofsuperintenselasersispresented.Asimplecriterionforradiationpressuredominanceatintensitiesaround5×1020Wcm-2isgiven,andthepossibilityforfastenergygainintherelativisticregimeisdiscussed.
简介:TheexcitonicopticalabsorptionofGaAsbulksemiconductorsunderintenseterahertz(THz)radiationisinvesti-gatednumerically.Themethodofsolvinginitial-valueproblems,combinedwiththeperfectmatchedlayertechnique,isusedtocalculatetheopticalsusceptibility.InthepresenceofadrivingTHzfield,inadditiontotheusualexcitonpeaks,2preplicaofthedark2pexcitonandeven-THz-photon-sidebandsofthemainexcitonresonanceemergeinthecontinuumabovethebandedgeandbelowthemainexcitonresonance.Moreover,tounderstandtheshiftofthepositionofthemainexcitonpeakunderintenseTHzradiation,itisnecessarytotakeintoconsiderationboththedynamicalFranz-KeldysheffectandacStarkeffectsimultaneously.Formoderatefrequencyfields,themainexcitonpeakdecreasesandbroadensduetothefield-inducedionizationoftheexcitonswithTHzfieldincreasing.However,forhighfrequencyTHzfields,thecharacteristicsoftheexcitonrecurevenunderverystrongTHzfields,whichaccordswiththerecentexperimentalresultsqualitatively.
简介:OurexperimentsshowthatexternalfocusingandinitiallaserenergystronglyinfluencesfilamentgeneratedbythefemtosecondTi–sapphirelaserinair.Theexperimentalmeasurementsshowthefilamentlengthcanbeextendedbothbyincreasingthelaserenergyandfocallengthoffocusinglens.Ontheotherhand,theplasmafluorescenceemissioncanbeenhancedbyincreasingthelaserenergywithfixedfocallengthordecreasingthefocallength.Inaddition,thecollapsedistancemeasuredexperimentallyarelargerthanthecalculatedonesowingtothegroup-velocity-dispersioneffect.Inaddition,wefindthatthelinewidthsofthespectrallinesfromN2isindependentoffilamentpositions,laserenergiesandexternalfocusing.
简介:Wepresentaninterferometrysetupandthedetailedfringeanalysismethodforintenseshortpulse(SP)laserexperiments.Theinterferometryschemewasrefinedthroughmultiplecampaignstoinvestigatetheeffectsofpre-plasmasonenergeticelectronsattheJupiterLaserFacilityatLawrenceLivermoreNationalLaboratory.Theinterferometerusedafrequencydoubled(λ=0.527μm)0.5pslongopticalprobebeamtomeasurethepre-plasmadensity,aninvaluableparametertobetterunderstandhowvaryingpre-plasmaconditionsaffectthecharacteristicsoftheenergeticelectrons.Thehardwareofthediagnostic,dataanalysisandexampledataarepresented.ThediagnosticsetupandtheanalysisprocedurecanbeemployedforanyotherSPlaserexperimentsandinterferograms,respectively.
简介:Strongfluorescenceemissionswereobservedfornitrogen,carbonmonoxide,andcarbondioxidemoleculesinintensefemtosecondlaserfields.Theseemissionscanbeassignedtothetransitionsofthemolecularionsfromtheexcitedelectronicstatestothegroundelectronicstates.Theformationmechanismswerediscussedandthelifetimesweremeasuredfortheseexcitedmolecularionsinintenselaserfields.
简介:Twocompactandintense2.45GHzpermanentprotonsourcesandtheircorrespondinglowenergybeamtransport(LEBT)systemsweredevelopedsuccessfullyforChinaAcceleratorDrivenSub-criticalsystem(C-ADS)in2014,oneofwhichwasbuiltatIMP,LanzhouandtheotheratIHEP,Beijing.Bothprotonsourcescandeliverstable10mA/35keVprotonbeamsatCWmodetotheentrancesofthedownstreamRFQs.AsshowninFig.1,thebeamsextractedbya3-electrodeextractionsystemaretransportedbytheLEBTsystem,whichiscomposedof2identicalsolenoids,andintothe3.2or2.1MeVradio-frequencyquadrupole(RFQ).Inordertoensuresuperconductingcavitiescommissioningandprotection,anelectrostatic-chopperhasbeendesignedandinstalledintheLEBTlinethatcanchopthecwbeamFig.2Totalhydrogenionbeamcurrentversusinputpower.intoapulsedone.Theachievedfall/risetimeofthechopperislessthan20ns.
简介:Itisfoundthatthereisanupper-limitcriticalpowerforself-guidedpropagationofintenselasersinplasmainadditiontothewell-knownlower-limitcriticalpowersetbytherelativisticeffect.Abovethisupper-limitcriticalpower,thelaserpulseexperiencesdefocusingduetoexpulsionoflocalplasmaelectronsbythetransverseponderomotiveforce.Associatedwiththeupper-limitpower,alower-limitcriticalplasmadensityisalsofoundforagivenlaserspotsize,belowwhichself-focusingdoesnotoccurforanylaserpower.Boththeupper-limitpowerandthelower-limitdensityarederivedtheoreticallyandverifiedbytwo-dimensionalparticle-in-cellsimulations.Thepresentstudyprovidesnewguidanceforexperimentaldesigns,whereself-guidedpropagationoflasersisessential.
简介:Wereportonatargetsystemsupportingautomatedpositioningofnano-targetswithaprecisionresolutionof4μminthreedimensions.Itreliesonaconfocaldistancesensorandamicroscope.Thesystemhasbeencommissionedtopositionnanometertargetswith1Hzrepetitionrate.Integratingourprototypeintothetable-topATLAS300TW-lasersystemattheLaboratoryforExtremePhotonicsinGarching,wedemonstratetheoperationofa0.5Hzlaser-drivenprotonsourcewithashot-to-shotvariationofthemaximumenergyabout27%foralevelofconfidenceof0.95.Thereasonoflasershootingexperimentsoperatedat0.5Hzratherthan1Hzisbecausethesynchronizationbetweenthenano-foiltargetpositioningsystemandthelasertriggerneedstoimprove.
简介:Thefirstexperimentalmeasurementsofintense(~7×1019Wcm-2)laser-driventerahertz(THz)radiationfromasolidtargetwhichispreheatedbyanintensepulseoflaser-acceleratedprotonsisreported.ThetotalenergyoftheTHzradiationisfoundtodecreasebyapproximatelyafactorof2comparedtoacoldtargetreference.Thisisattributedtoanincreaseinthescalelengthofthepreformedplasma,drivenbyprotonheating,atthefrontsurfaceofthetarget,wheretheTHzradiationisgenerated.TheresultsshowtheimportanceofcontrollingthepreplasmascalelengthforTHzproduction.
简介:Inthepresentpapertheproblemofnonlinearinteractionoftwomildly-relativisticcircularlypolarizedlasersinacoldplasmaisstudiedinordertoinvestigateelectromagneticallyinducedtransparency(EIT).Basedonarelativistickineticmodel,byexpansionofrelativisticLorentzfactorintermsoflasersamplitude,weobtainthecouplednonlineardispersionrelations.Itisobservedthatduetoresonanceinthesecondharmonicofplasmabeat-wave,thenewEITpass-bandiscreatedinthehighintensitiesoflasers.Theeffectofamplitudeandfrequencyvariationonthedispersionisnumericallyinvestigated.
简介:一个二维的电磁的Particle-in-Cell(照片)模拟模型被建议与横梁宽度w学习强烈离子横梁的繁殖与电子皮肤深度c/相比小的b通过背景血浆的pe面对外部应用磁场。有效电子gyroradiusw<潜水艇class=“a-plus-plus”>ge被发现面对磁场是为离子横梁运输的一个重要参数。在横梁区域,背景血浆对宽度w的离子横梁不同地作出回应b
简介:Wedemonstratedexperimentallytheformationofmonoenergeticbeamsofacceleratedelectronsbyfocusingfemtosecondlaserradiationwithanintensityof2×1017W/cm2ontotheedgeofanaluminumfoil.Theelectronshadenergydistributionspeakinginthe0.2–0.8MeVrangewithenergyspreadlessthan20%.Theaccelerationmechanismrelatedtothegenerationofaplasmawaveasaresultofself-modulationinstabilityofalaserpulseinadenseplasmaformedbyaprepulse(arriving12nsbeforethemainpulse)isconsidered.One-dimensionalandtwo-dimensionalParticleinCell(PIC)simulationsofthelaser–plasmainteractionshowedthateffectiveexcitationofaplasmawaveaswellastrappingandaccelerationofanelectronbeamwithanenergyontheorderof1MeVmayoccurinthepresenceofsharpgradientsinplasmadensityandinthetemporalshapeofthepulse.
简介:Thephotonemissionspectrumofthehydrogenatomsinanintensehigh-frequencylaserpulseissimulatedbyusingone-dimensionalsoftCoulombpotential.Regularfinestructuresappearonthetwosidesofboththeoddandevenmultiplesofphotonenergyofthelaserfieldbesidestheordinaryoddharmonicpeaks.Itisprovedthatthesplitsofthefinestructuresareresponsibleforhyper-RamanlinesandtheenergyspacingbetweentheoddharmoniclinesisequaltothedifferenceinenergybetweentheeigenstateswiththesameparityofthetimeaveragedKrameters-Henneberger(KH)potential.Byanalysingthefeaturesofthefinestructures,wealsoverifythattheso-calledevenorderharmonicsunderthestabilizationconditionareindeedhyper-Ramanlinescausedbythetransitionsbetweenthedressedatomicstateswithdifferentvaluesofparity.