High Power Laser-Matter Interaction

Inthepresentvolumethemainaspectsofhigh-powerlaser–matterinteractionin 10 22 2 theintensityrange10 –10 W/cm aredescribed. Weofferaguidetothistopic forscientistsandstudentswhohavejustdiscoveredthe eldasanewandattractive areaofresearch,andforscientistswhohaveworkedinanother eldandwantto joinnowthesubjectoflaserplasmas. Beingawareofthewidedifferencesinthe degreeofmathematicalpreparationtheindividualcandidatehasacquiredwetried topresentthesubjectinanalmostself-containedmanner. Tobemorespeci c,a bachelordegreeinphysicsenablesthereaderinanycasetofollowwithoutdi- culty. Generally uidorgasdynamicsanditsrelativisticversionisnotapartof thiseducation;itisdevelopedinthecontextwhereitisneeded. Basicknowledgein theoreticalmechanics,electrodynamicsandquantumphysicsaretheonlyprereq- sitesweexpectfromthereader. Throughoutthebookthemainemphasisisonthe variousbasicphenomenaandtheirunderlyingphysics. Notmoremathematicsthan necessaryisintroduced. Thepreferenceisgiventoideas. Agoodmodelisthebest guidetotheadequatemathematics. Thereexistalreadysomebutnotsomany, however, goodvolumesandsome monographsonhigh-powerlaserinteractionwithmatter. Afterresearchinthis eld hasgrownoverhalfacenturyandhasrami edintomanybranchesoffundamental studiesandapplicationsproducingcontinuouslynewresults,thereisnoindication ofsaturationorlossofattraction,ratherhasexcitementincreasedwiththeyears: “Therearenolimits;horizonsonly”(G. A. Mourou). Wetakethisasamotivation foranewattemptofpresentingourintroductiontotheachievementsfromthebeg- ninguptopresent. Anadditionalaimwastoofferamoreuni edormoredetailed viewwherethisispossiblenow. Furthermore,thereadermay ndconsiderations not encountered in existing volumes on the eld, e. g. , on ideal uid dynamics, dimensionalanalysis,questionsofclassicaloptics,instabilitiesandlightpressure. Inviewoftherapidlygrowing eldofatoms,moleculesandclustersexposedto superstronglaser eldsweconsidereditascompulsorytodedicateanentirechapter tolaser–atominteractionandtothevariousmoderntheoreticalapproachesrelated toit. Finally,aconsistentmodelofcollisionlessabsorptionisgiven. Dependingonpersonalpreferencesthereadermaymissperhapsasectionon inertialfusion,onhighharmonicgenerationandonradiationfromtheplasma,or ontraditionalatomicandionicspectroscopy. Inviewofthespecializedliterature vii viii Preface alreadyavailableonthesubjectswethinktheself-imposedrestrictionisjusti ed. Ourreferencingpracticewasguidedbyindicatingmaterialforsupplementaryst- iesandestablishingacontinuitythroughthedecadesofresearchinthe eldrather thanbytheaimofcompleteness. Thelatternowadaysiseasilyachievablewiththe aidoftheInternet. Wehavetestedthetextwithrespecttocomprehensionandreadability. Our rst thanksgotoProf. EdithBoriefromtheForschungszentrumKarlsruhe. Shepro- readgreatpartsofthetextverycarefullyandgavevaluablecomments. Insecond placewewouldliketothankMrs. ChristineEidmannfromTheoreticalQuantum A Electronics (TQE), TU Darmstadt, for typing in LTX half of the book. We are E furtherindebtedtoProf. RudolfBockfromGSI,Darmstadt,forhelpfuldiscussions andprecioushints. Furtherthanksforhelpfuldiscussions,criticalcomments,che- ingformulasgotoDr. HerbertSchnabl,Prof. WernerScheid,Dr. RalfSchneider, Dipl. -Phys. TatjanaMuth,Dr. SteffenHain,andDr. FrancescoCeccherini. Wewant toacknowledgeexplicitlythecontinuouseffortandsupportinpreparingthe nal manuscript by Dr. Su-Ming Weng from the Insitute of Physics, CAS, China, at presentfellowoftheHumboldtFoundationatTQE. Forhisprofessionalinputto thesectiononBrillouinscatteringspecialthanksgotoDr. StefanHüllerfromEcole PolytechniqueinPalaiseau. Darmstadt,Germany PeterMulser Rostock,Germany DieterBauer Contents 1 Introductory Remarks and Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 2 The Laser Plasma: Basic Phenomena and Laws. . . . . . . . . . . . . . . . . . . . 5 2. 1 Laser–ParticleInteractionandPlasmaFormation. . . . . . . . . . . . . . . . . 6 2. 1. 1 High-PowerLaserFields. . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 2. 1. 2 SingleFreeElectronintheLaserField(Nonrelativistic). . 9 2. 1. 3 CollisionalIonization,PlasmaHeating,andQuasineutrality 13 2. 2 FluidDescriptionofaPlasma. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24 2. 2. 1 Two-FluidandOne-FluidModels. . . . . . . . . . . . . . . . . . . . . 24 2. 2. 2 LinearizedMotions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37 2. 2. 3 SimilaritySolutions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44 2. 3 LaserPlasmaDynamics. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 58 2. 3. 1 PlasmaProductionwithIntenseShortPulses . . . . . . . . . . . 60 2. 3. 2 HeatingwithLongPulsesofConstantIntensity. . . . . . . . . 63 2. 3. 3 SimilarityConsiderations. . . . . . . . . . . . . . . . . . . . . . . . . . . . 69 2. 4 SteadyStateAblation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 74 2. 4. 1 TheCriticalMachNumberinaStationaryPlanarFlow. . . 75 2. 4. 2 AblativeLaserIntensity. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 78 2. 4. 3 AblationPressureintheAbsenceofPro leSteepening. . . 82 References. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 85 3 Laser Light Propagation and Collisional Absorption . . . . . . . . . . . . . . .