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Laser developments and high resolution resonance ionization spectroscopy of actinide elements PDF

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Preview Laser developments and high resolution resonance ionization spectroscopy of actinide elements

DEPARTMENTOFPHYSICS UNIVERSITYOFJYVÄSKYLÄ RESEARCHREPORTNO. 1/2015 Laser developments and high resolution resonance ionization spectroscopy of actinide elements by Volker Sonnenschein Academic Dissertation for the Degree of Doctor of Philosophy Tobepresented,bypermissionofthe FacultyofMathematicsandNaturalSciences oftheUniversityofJyväskylä, forpublicexaminationinAuditoriumYAA303ofthe UniversityofJyväskyläonJanuary8th,2015 at12o’clocknoon Jyväskylä,Finland December2014 ABSTRACT Sonnenschein,Volker Laser developments and high resolution resonance ionization spectroscopy of actinide elements Jyväskylä: UniversityofJyväskylä,2014,176p. DepartmentofPhysicsResearchReport ISSN0075-465X;1/2015) ISBN978-951-39-6049-0(paperversion) ISBN978-951-39-6050-6(electronicversion) Diss. LaserdevelopmentofpulsedTi:sapphirelasersystemshasbeencarriedoutatthe IGISOLfacilityintheUniversityofJyväskylä,Finland. Tofurthertheapplications ofTi:sapphiretechnologyinthedomainofresonancelaserionization,severalnew laser resonator designshave been implemented. Studiesfor the development of ionization schemes have been simplified by use of a grating-based cavity. For increased spectroscopic resolution a dual-etalon as well as an injection-locked Ti:sapphire laser have been built and characterized. Increased output power of higherharmonicshasbeenachievedwiththetechniqueofintra-cavityfrequency doubling. Extensiontoanewfrequencydomainhasbeenrealizedusingdifference frequencymixing. These new developments have been successfully applied in experimental studiesattheUniversityofMainz(Germany),theLISOLfacility(Belgium)aswell as at IGISOL (Finland). High resolution resonance ionization spectroscopy has been used to study the ground state hyperfine structure of 229Th in an ongoing effort to identify a highly sought after nuclear isomer. Further high resolution workhasbeencarriedouton227Acaswellasseveralisotopesofplutonium. Sys- tematic studiesof the hyperfinestructure of naturalcopper have beenemployed todeterminetheaccuracyoffuturein-sourcelaserspectroscopyapplicationsat IGISOL. Keywords:Resonanceionization,laser,Ti:sapphire,hyperfinestructure Author VolkerSonnenschein DepartmentofPhysics UniversityofJyväskylä Finland Supervisor Dr. IainMoore DepartmentofPhysics UniversityofJyväskylä Finland Reviewers Prof. GerdaNeyens KULeuven NuclearandRadiationPhysicsSection Celestijnenlaan200d-box2418 3001Leuven,Belgium and Dr. PaulCampbell TheSchoolofPhysicsandAstronomy UniversityofManchester OxfordRoad Manchester M139PL,UK Opponent Prof. JonBillowes TheSchoolofPhysicsandAstronomy UniversityofManchester OxfordRoad Manchester M139PL,UK PREFACE This work hasbeen carried out at theAccelerator Laboratory of theDepartment ofPhysics, UniversityofJyväskylä,Finland from2009to2014. Financial support from the Graduate School for Particle and Nuclear Physics (GRASPANP), the DoctoralProgrammeinParticleandNuclearPhysics(PANU)andtheUniversity ofJyväskyläisgreatlyappreciated. ACKNOWLEDGEMENTS I am grateful to Prof. Juha Äystö for taking me into the group as well as for the continuedsupportfromhissuccessorProf. AriJokinen. Iwanttothankthewhole IGISOL group for a great working experience and support during the on- and off-linelaserruns. SpecialmentiongoestothepeopleoftheIGISOL-lasersubunit. Mysuper- visor Dr. Iain Moore for his ever-present guidance and contagious motivation. Mikael Reponen for his introduction to the local nightlife and the shared wasted hours tweaking laser systems underthe green sun. Thomas Kessler is acknowl- edgedforhisintroductiontothelasersystems,IlkkaPohjalainenforhiscontribu- tions to the data acquisition system and Annika Voss for her recent support on laserspectroscopy. Iamindebtedtoallourcollaboratorsforallowingmetotakepartinseveral interesting experiments. Thanks goto RafaelFerrer andYuri Kudryavtsevat the LISOL facility, Tetsuo Sonoda and Michiharu Wada at RIKEN, Hideki Tomita fromNagoyaandNathalieLecesneatGANIL.Ialsowanttoexpressmygratitude to my german supervisor Prof. Klaus Wendt and his group, as many of these opportunitiesandfurtherexperimentsatMainzweresetinmotionthroughtheir efforts. Thanksgotohiscurrentandformergroupmembersfortheircontributions, discussions as well as some wicked kicker games. Great thanks go to Sebastian Raeder,withoutwhomtheexperimentsinMainzlikelywouldnothavebeenthat successful. Furthermore, iam gratefulto thelocal staff ofthe mechanicaland electrical workshop,whohavebroughtmydesignsandideasintorealityandhelpedgreatly during the move to IGISOL 4. I also want to thank the secretaries for their kind support and for not getting fed up with all my equipment orders and other administrativeneeds. CheerstoSebastianRotheforthelatenightbrainstormingsessionsonlaser constructionandcheersaswelltomyconspiratorsforgalacticdominationTommi andTobias-‘‘Fortheswarm!’’. Ich bedanke mich bei meiner Familie und meinen Großeltern für die lang- jährige Unterstützung und Interesse an meinem Fortschritt und Wohlergehen. Danke auch an meine Frau für die willkommene Abwechslung von der Arbeits- routine ‘‘完了!牛逼了!’’. LIST OF INCLUDED ARTICLES This thesisis basedon thesix publications listedbelow. The authorhad a major contribution to experiment, analysis and writing of articles I and IV and is the main author for publications II, III, V and VI. The author has been involved in several international experiments. These include laser spectroscopic studies on thorium,actiniumandplutoniumattheUniversityofMainz,firstlaserionization tests with the new Ti:sapphire laser system in GANIL, the comparison of a dye andTi:sapphirelasersystematLISOL(ArticleI),firsttestsofin-jetlaserionization of niobium with Ti:sapphire lasers at the PALIS prototype system at RIKEN andinvolvementinthesettingupofaninjection-lockedTi:sapphirelaseratthe UniversityofNagoya. Furthermore,theauthorhaswonthe2013LA3NETprize, inpartduetothecontributiontotheseexperiments. ArticleI: Performance of a high repetition pulse rate laser system for in-gas-jet laser ionizationstudieswiththeleuvenlaserionsource@LISOL. R.Ferrer,V.T.Sonnenschein,B.Bastin,S.Franchoo,M.Huyse,Yu. Kudryavt- sev, T. Kron, N. Lecesne, I.D. Moore, B. Osmond, D. Pauwels, D. Radulov, S. Raeder, L. Rens, M. Reponen, J. Roßnagel, H. Savajols, T. Sonoda, J.C. Thomas,P.VandenBergh,P.VanDuppen,K.Wendt,andS.Zemlyanoy. NIMB291,29–37,2012. ArticleII: IntracavityFrequencyDoublingandDifferenceFrequencyMixingforPulsed nsTi:sapphireLaserSystemsatOn-lineRadioactiveIonBeamFacilities V. Sonnenschein, I. D. Moore, I. Pohjalainen, M. Reponen, S. Rothe and K. Wendt. Acceptedforpublication(JPSConf. Proc.,2014). ArticleIII: Characterizationofadual-etalonTi:sapphirelaserviaresonanceionization spectroscopyofstablecopperisotopes. V.Sonnenschein,I.D.Moore,H.Khan,I.PohjalainenandM.Reponen. HyperfineInteractions227,113-123,2014. ArticleIV: Resonance ionization spectroscopy of thorium isotopes - towards a laser spectroscopicidentificationofthelow-lying7.6eVisomerof229Th. S.Raeder,V.Sonnenschein,T.Gottwald,I.D.Moore,M.Reponen,S.Rothe, N.Trautmann,andK.Wendt. J.Phys. B44,165005,2011. ArticleV: Thesearchfortheexistenceof229mThatIGISOL. V.Sonnenschein,I.D.Moore,S.Raeder,A.Hakimi,A.Popov,andK.Wendt. Eur. Phys. J.A.48,52,2012. ArticleVI: Determinationoftheground-statehyperfinestructureinneutral229Th. V.Sonnenschein,S.Raeder,A.Hakimi,I.D.MooreandK.Wendt J.Phys. B45,165005,2012. LIST OF FIGURES FIGURE1 International facilities for on- and offline studies of exotic iso- topesusinglaserionsources.................................................. 18 FIGURE2 ComparisonofLorentzian,GaussianandVoigtprofiles........... 24 FIGURE3 Propagationofarayoflightalongtheopticalaxisinfreespace. 28 FIGURE4 Refractionofarayatacurvedsurface .................................... 29 FIGURE5 PropagationofaGaussianbeamclosetothefocalspot............. 33 FIGURE6 PhasematchinganglesforSHGusingaBBOcrystal................. 40 FIGURE7 LevelstructureoftheTi:sagainmedium................................. 41 FIGURE8 EmissionandabsorptionbandsoftheTi:sapphiremedium ...... 42 FIGURE9 SimulationofTi:sapulsedynamics......................................... 44 FIGURE10 Transmissionoflightthroughanetalon.................................. 45 FIGURE11 TransmissioncurveofanetalonwithaFSRof10GHz ............. 46 FIGURE12 Calculations for the first Jones matrix element M of a bire- pp fringentquartzplate ............................................................. 49 FIGURE13 Simulatedtransmissioncurveforbirefringentfilter ................. 50 FIGURE14 Diffractionatagrating .......................................................... 51 FIGURE15 LayoutofthecurrentlasersetupatFURIOS............................ 54 FIGURE16 Powerscalingvsdiodecurrentofpumplasers........................ 55 FIGURE17 StandardTi:salasercavity..................................................... 56 FIGURE18 Wavemeter measurement of HeNe laser showing fibre and temperaturedependentfluctuations....................................... 57 FIGURE19 Fourthharmonicoutputpowerusingic-SHGgenerated450nm radiation.............................................................................. 60 FIGURE20 Tuning curve of mirror set MS4a for both fundamental and SHGradiation ...................................................................... 61 FIGURE21 3DCADdesignofthegrating-basedTi:salaser ....................... 65 FIGURE22 Pathoflaserbeamthroughafourprismbeamexpander.......... 66 FIGURE23 OutputpowervspumppowerforthegratingTi:salasermea- suredat780nm .................................................................... 67 FIGURE24 Mode waist calculation of the grating laser with the original ◦ foldingangleof35.5 ............................................................ 68 FIGURE25 Modewaistcalculationofthegratinglaserwiththeoptimized ◦ foldingangleof32 ............................................................... 68 FIGURE26 Tuningcurvesforthegratinglaserusingthebroadbandmirror set ....................................................................................... 69 FIGURE27 Ti:samode-waistforasymmetricandsymmetriccrystalposi- tioning................................................................................. 70 FIGURE28 Tuningcurve measuredwiththe Ti:sacrystalcentred between thecurvedfoldingmirrors..................................................... 71 FIGURE29 Laserexcitationandionizationschemesofsamariumusedfor the search for new high-lying excited states and autoionizing states. .................................................................................. 72 FIGURE30 IoncountratedistributionandcomparisonwithPoissondis- tribution .............................................................................. 73 FIGURE31 Effectofthecut-offthreshold n onthenumberofdetectedpeaks. 74 FIGURE32 Smallexcerptofascanforsecondexcitedstates ...................... 75 FIGURE33 Higher-lyingatomicstatesinsamarium.................................. 76 FIGURE34 Comparisonof ion signalgenerated usingdifferent ionization lasers................................................................................... 77 FIGURE35 Severalscansforautoionizingresonances............................... 80 FIGURE36 Severalidentifiedionizationschemesforsamarium................. 81 FIGURE37 Saturationcurvesofexcitationsteps1-3.................................. 82 FIGURE38 Single-passtransmissioncurvesofthetwoetalons................... 87 FIGURE39 Zoomed-inviewofthetransmissioncurvesshowingthemode structureoftheTi:sacavity.................................................... 88 FIGURE40 Rateequationresultforthelinewidthusingthesinglethinetalon 89 FIGURE41 Rateequationresultforthelinewidthusingthedualetalon...... 90 FIGURE42 Photographoftheself-madescanningFPI............................... 90 FIGURE43 Simulationofthemode-matchingtotheFPIcavity .................. 91 FIGURE44 Photodiode signals of the HeNe and Ti:sa laser during a full voltagerampoftheplaneparallelFPI..................................... 92 FIGURE45 FPItransmissionpeakseparationvs. peaknumber.................. 93 FIGURE46 scanofthesemi-hemisphericalFPI......................................... 94 FIGURE47 TimingofHeNepeaksagainstFSRnumber ............................ 95 FIGURE48 D1lineinRubidiumandhyperfineshifts................................ 96 FIGURE49 Saturationabsorptionspectroscopysetupforrubidium............ 97 FIGURE50 Signal ofprobe and reference beamduring scan of therubid- iumhyperfinestructure......................................................... 98 FIGURE51 Hyperfinestructureofnaturalrubidium................................. 99 FIGURE52 Overviewofthesetupoftheinjection-lockedTi:salasersystem.102 FIGURE53 3DCADdesignofthecavity..................................................104 FIGURE54 Ti:samode-waistalongthecavityforthe"design"crystallength of20mmandre-polishedcrystallengthof18.3mm .................105 FIGURE55 Passive resonator stability analysis by monitoring the photodi- odeoutputoscillations ..........................................................107 FIGURE56 Transmissionfringesofthecavitywithandwithoutdithering..107 FIGURE57 Resonances of the piezo actuator frequency response curve andphaseshift .....................................................................108 FIGURE58 Softwareinterfaceofthelock-box...........................................109 FIGURE59 Photo-diode and lock-in signal with and without the 10kHz trigger .................................................................................110 FIGURE60 Photodiodeandlock-insignalwiththecavitylocked...............110 FIGURE61 Seededoutputpowervs. pumppower. ..................................111 FIGURE62 SeededTi:sa signalin theFPI(1GHzFSR) showingtwo trans- missionpeaks.......................................................................112 FIGURE63 FPIspectrumatdifferentTi:sapowerlevels............................113 FIGURE64 LinewidthdependenceonTi:saoutputpowerandpumppower113 FIGURE65 Wavelengthtuningcurvewithbroadbandmirrorset...............115 FIGURE66 Wavelengthtuningcurvewithamixedmirrorset ...................116 FIGURE67 Seedefficiencydependenceoninjectedpowerat725nm,745nm and775nmwithmixedmirrorset. .........................................116 FIGURE68 Power required to achieve 95% seed efficiency as calculated fromrateequations...............................................................118 FIGURE69 Simulated transmissioncurves of thesingle plate birefringent filterinsertedatBrewsterangle..............................................119 FIGURE70 Tuningrangewithandwithoutthebirefringentfilterplate.......119 FIGURE71 Viewlookingdownintotheatomicbeamunit(ABU)showing thecollimatingslitandionoptics. ..........................................120 FIGURE72 Single scan of the 244nm transition in CuI illustrating the hyperfinestructure ...............................................................122 FIGURE73 Saturationofthe244nmtransitioninCuI...............................125 FIGURE74 Effectoffirststepintensityonhyperfinecomponentamplitude andwidth ............................................................................125 FIGURE75 Photodiodesignalsofexcitationandionizationlaserpulse.......127 FIGURE76 Dependenceofionsignalonionizationpulsedelaytime..........127 FIGURE77 DependenceofLorentzianlinewidthonionizationpulsedelay.128 FIGURE78 Effect ofionization pulse delayon hyperfine component am- plitudeandwidth.................................................................129 FIGURE79 Hyperfineparametersforeachofthe12copperscans ..............130 FIGURE80 Setupoftheinjection-lockedTi:safortheactiniumandpluto- niumexperiment,seetextfordetails.......................................132 FIGURE81 Oscillsocope trace of the spectrum of the seeded Ti:sa in the confocalFPIinMainz............................................................133 FIGURE82 Broadbandlaser systemsforthe ionizationstep,optical path andtheMainzAtomicBeamunit(MABU)..............................134 FIGURE83 3DschematicillustratingtheworkingprincipleoftheMABU system.................................................................................135 FIGURE84 Transitions in actinium probed for hyperfine structure with theinjectionlockedTi:sasystem.............................................136 FIGURE85 Actiniumhyperfinestructure-transitionA(388.67nm). Data inblack,fit curveinred. Dashedlinesindicatethepositionof theHFScomponentsandarelabeledwiththeF→F’notation....136 FIGURE86 Actiniumhyperfinestructure-transitionB(438.58nm)............137 FIGURE87 Actiniumhyperfinestructure-transitionC(383.64nm)............137 FIGURE88 Actiniumhyperfinestructure-transitionD(419.56nm). The verylow statisticsatthe rightmost peaksaredue totheatomic sampleexhaustion. Alargerbinwidthof60MHzwasusedfor thistransition. ......................................................................137 FIGURE89 Actiniumhyperfinestructure-transitionE(439.79nm)............138 FIGURE90 Ionizationschemesforplutoniumusedtodeterminehyperfine structureandisotopeshifts....................................................140

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The School of Physics and Astronomy. University of Sirah Matisse TS. Table 3 .. FIGURE 22 Sketch of the path of the laser beam through the four-prism beam expander .. more time consuming manual approach was taken.
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