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Publié par | ruprecht-karls-universitat_heidelberg |
Publié le | 01 janvier 2010 |
Nombre de lectures | 24 |
Langue | English |
Poids de l'ouvrage | 3 Mo |
Extrait
Dissertation
submittedtothe
CombinedFacultiesfortheNaturalSciencesandforMathematics
oftheRupertus-CarolaUniversityofHeidelberg,Germany
forthedegreeof
DoctorofNaturalSciences
Putforwardby
Master-Phys.:AlexeySokolov
Bornin:Kingisepp,Russia
Oralexamination:29.01.2010
ECBhISar/gTeabnredecdoilnligsiionnvessttuigdaytioofniionns
withcoldatomsforHITRAP
Referees:
Priv.Doz.Dr.WolfgangQuint
Prof.Dr.AndreasWolf
UntersuchungenzumLadungsbru¨teninEBIS/TundKollisionsex-
perimentemitkaltenAtomenfu¨rHITRAPLangsameodersichin
RuhebendlichehochgeladeneIonensindinteressanteSystemefu¨ratom-
physikalischeExperimente.Fu¨rUntersuchungenanschwerenhochgeladenen
IonenwurdedieIonenfallenanlageHITRAP(Highlychargediontrap)ander
GSI/Darmstadtaufgebaut,diegeku¨hlteStrahlenhochgeladenerIonenbei
einerEnergievon5keV/qliefernwird.DiehochgeladenenIonenwerdenin
einerStripper-FoliebeirelativistischenEnergienerzeugtundimExperimen-
tierspeicherringESRundinderHITRAP-Anlageabgebremst,bevorsiezu
denExperimentengeliefertwerden.EinExperimentistderMehrelektronen-
LadungsaustauschinSto¨ßenhochgeladenerIonenmitkaltenAtomen,die
mitderMOTRIMS-Methodeerforschtwerden.EinStoßexperimentmitle-
ichtenIonenauseinerEZR-IonenquelleundkaltenAtomenineinermagne-
tooptischenFallealsTargetwurdedurchgefu¨hrtunddieResultatewerden
dargestellt.EineElektronenstrahl-Ionenfalle(EBIT)fu¨rdieInbetriebnahme
derHITRAP-Experimentewurdegetestetundoptimiert.DerProzessdes
Ladungsbru¨tenswurdeinderEBITerfolgreichmitEdelgasenundeinem
Alkali-Element,dasauseinerexternenIonenquelleeingeschossenwurde,er-
folgreichuntersucht.
ChargebreedinginvestigationinEBIS/Tandcollisionstudyofions
withcoldatomsforHITRAPHighlychargedions(HCI)atlowvelocities
oratrestareinterestingsystemsforvariousatomicphysicsexperiments.For
investigationsonHCIofheavystableorradioactivenuclidestheHITRAP
(HighlychargedIonTRAP)deceleratorfacilityhasbeensetupatGSIto
delivercooledbeamsofHCIatanenergyof5keV/q.TheHCIareproduced
inastripperfoilatrelativisticenergiesandaredeceleratedinseveralsteps
atESRstorageringandHITRAPbeforetheyaredeliveredtoexperimental
setups.Oneoftheexperimentsistheinvestigationofmulti-electroncharge
exchangeincollisionsofheavyHCIwithcoldatomsusingnovelMOTRIMS
technique.CollisionexperimentsonlightionsfromanECRionsourcecol-
lidingwithcoldatomsinaMOThavebeenperformedandtheresultsare
described.Anelectronbeamiontrap(EBIT)hasbeentestedandopti-
mizedforcommissioningoftheHITRAPphysicsexperiments.Theprocess
ofchargebreedingintheEBIThasbeensuccessfullystudiedwithgaseous
elementsandwithanalkalineelementinjectedfromanexternalionsource.
Themachinedoesnotisolate
plungeshimmoredeeplyinto
manfrom
t.meh
eht
taerg
problemsofnaturebut
AntoinedeSaint-Exupery
Contents
1GeneralIntroduction1
2HITRAP5
2.1Overview...............................5
2.1.1Double-DriftBuncher....................8
2.1.2IH-structure.........................11
2.1.3RFQandLEBTsection..................12
2.1.4CoolerTrapandbeamlinetoexperiments........14
2.2HITRAPexperiments.......................15
2.2.1g-factormeasurements..................15
2.2.2Massmeasurements.....................16
2.2.3Laserspectroscopy.....................17
3TheoryofIon-Atomcollisions19
3.1Introduction.............................19
3.2Perturbationtheory.........................20
3.3Ion-atominteractionsatdierentvelocities...........22
3.3.1Highvelocity........................24
3.3.2Intermediatevelocity....................24
3.3.3Lowvelocity.........................26
3.4Classicalover-barriermodel....................29
3.5Statisticalinterpretationoftransferionization..........32
4Ion-Atomcollisionexperiment35
4.1Ion-atomcollisionkinematics...................35
4.2Experimentalmethods.......................37
4.3MOTRIMSsetupatKVI......................40
4.3.1MOT.............................41
4.3.2RIMS............................42
4.3.3Experimentalresultsanddiscussion............43
5Ionsources51
5.1EBIS/T...............................51
5.1.1Introduction.........................51
5.1.2Ioncreation.........................53
I
IICONTENTS
5.1.3Ionchargeexchange....................54
5.1.4Electronbeam........................55
5.1.5Iontemperature.......................57
5.2ECRIS................................58
5.3Singlychargedionsources.....................60
6EBIS/Tsetupsandexperiments61
6.1MAXEBISsetupandexperiments.................61
6.2SPARCEBITsetupandexperiments...............66
6.2.1SPARCEBITsetup....................66
6.2.2Emittancemeasurements.................68
6.2.3Extractionpulsemeasurements..............70
6.2.4Chargestatespectra....................71
6.2.5X-rayspectra........................76
7ChargeBreedingofexternallyinjectedsinglychargedions79
7.1Motivation..............................79
7.2Basicsofchargebreeding......................81
7.3AdvancedchargebreedinginMAXEBIS.............82
7.4ChargebreedingintheroomtemperatureEBITs........84
8Summaryandoutlook93
AAtomicunits97
BMagneticeldincaseofcylindricalsymmetry99
CEmittancemeasurementsusing3-(multi-)gradientmethod101
Bibliography105
Acknowledgements113
ListofAcronyms115
ListofTables
1.2
1.3
44..12
1.A
Parametersofthedeceleratorelements.................
CrosssectionsforA12+Rb(Mg)collisionfromCBMmodel....
Q-valuesandreferencetotalcapturecrosssections.........
DierentcrosssectionsforHe2+Nacollisions...........
Atomicunits................................
III
7
13
6449
79
VI
TSIL
FO
TABLES
ListofFigures
2.1OverviewoftheGSIacceleratorcomplex................
2.2ExperimentalStorageRing.......................
2.3TheHITRAPbeamline.........................
2.4Double-DriftBuncher..........................
2.5IonbeamcurrentbeforeandaftertheDDB..............
2.6IonbeambunchesaftertheDDB....................
2.7InterdigitalH-type(IH)structure....................
2.8Signalsfromthesinglecrystaldiamonddetector...........
2.9AnalysisoftheionsignalsaftertheIH-structure...........
2.10Radiofrequencyquadrupole.......................
2.11CoolerTrap................................
3.1Possibleprocessesinion-atomcollisions...............
3.2TheMadison-Merzbachermap.....................
3.3Thomasmechanism...........................
3.4Capturecrosssections,comparisonwiththeBLmodel........
3.5MgionizationcrosssectionsfromRutherfordformula.........
3.6Schematicdiagramofpotentialcurvesforelectroncapture......
3.7CrosssectionsforA10+NacollisionfromCBMmodel.......
3.8FractionsofRb(1+n)+inArq+Rbcollisionfromstatisticalmodel.
4.1Geometriesforrecoilionmomentainvestigations...........
4.2HeidelbergRIMSanditssimulationusingSIMION7.0........
4.3Magneto-opticaltrap...........................
4.4RecoilIonMomentumSpectrometer..................
4.52DpatternofrecoilionsontheRIMSdetector............
4.6Q-valuespectrumoftheNa1+recoilions..............
4.7TheresultingelectroncapturecrosssectionsforHe2+Nacollisions
4.8TheresultingionizationcrosssectionsforHe2+Nacollisions...
5.1EBISsketch................................
5.2CBSIMsimulationofoxygenchargestateabundances........
5.3Dierentionspeciesinthetrap.....................
5.4ECRIS...................................
5.5Singlychargedionsource........................
6.1MAXEBISsetupatGSI.........................
V
5789901112131414102324262728203438393143444748494255585950626
IV
LISTOFFIGURES
6.2SimulationoftheMAXEBISsetup...................63
6.3Calculatedandsimulatedmagneticeld................64
6.4Abeamspotonthescreenandsimulatedphasespaceellipse....64
6.5TOFspectraindependenceonconnementtime...........65
6.6ExtractionpulsefromtheEBIS,dependenceonconnementtime..66
6.7SPARCEBITsetupatGSI.......................67
6.8SimulationsoftheSPARCEBITpotentials..............68
6.9Beamprolesandasimulationtoobtainafocallength........69
6.10Arionbeamemittanceindependenceontheelectroncurrent....69
6.11Dependenceofionextractionpulsesontheelectroncurrent.....71
6.12Dependenceofionextractionpulsesonconnementtime......72
6.13Magneticscansfordierentconnementtimes............73
6.14TOFspectraforlongconnementtimes................74
6.15Chargedistributionafter50msand1000msfordierentpressures.75
6.16Chargestatesabundanceoncon