Quantitative time resolved neutron imaging methods at the high flux neutron source FRM-II [Elektronische Ressource] / Johannes Brunner

Description

Technischen Universit¨at Munc¨ henFakultat¨ fur¨ PhysikInstitut fur¨ Experimentalphysik E21Quantitative time resolved neutronimaging methods at the high flux neutronsource FRM-IIJohannes BrunnerVollst¨andiger Abdruck der von der Fakult¨at fur¨ Physikder Technischen Universit¨at Munc¨ hen zur Erlangung des akademischen Grades einesDoktors der Naturwissenschaftengenehmigten Dissertation.Vorsitzender: Univ. Prof. Dr. M. KleberPruf¨ er der Dissertation: 1. Univ. Prof. Dr. P. B¨oni2. Univ. Prof. Dr. W. PetryDie Dissertation wurde am 19.09.2005 bei der Technischen Universit¨at Mu¨nchen ein-gereicht und durch die Fakult¨at fu¨r Physik am 01.03.2006 angenommen.”One picture is worth a thousand words”chinese sayingAbstractEnglishIn the current work various new experimental methods and computation proceduresin the field of neutron imaging are presented. These methods have a significant technicalimportance in non-destructive material investigations.Withstroboscopicneutronradiographyperiodicprocessescanbeinvestigatedonasub-millisecond time scale. This opens great opportunities for the study and the developmentof combustion engines.Energy selective time of flight neutron radiography at neutron spallation sources usesthe energy dependence of the neutron cross section to distinguish between materials. Theenergy resolution of this technique is very good and allows the identification of specificmaterials.

Sujets

• Physik

Informations

• Publié par: technische_universitat_munchen
• Publié le: 01 janvier 2006
• Nombre de lectures: 25
• Langue: English
• Poids de l'ouvrage: 42 Mo

Extrait

TechnischenUniversit¨atM¨unchen
Fakult¨atf¨urPhysik
Institutf¨urExperimentalphysikE21

Quantitativetimeresolvedneutron
imagingmethodsatthehighfluxneutron
IFRM-Isource

BrunnersneJohan

Vollst¨andigerAbdruckdervonderFakult¨atf¨urPhysik
derTechnischenUniversit¨atM¨unchenzurErlangungdesakademischenGradeseines
DoktorsderNaturwissenschaften
.ertationDissgenehmigten

Vorsitzender:Univ.Prof.Dr.M.Kleber
Pr¨uferderDissertation:1.Univ.Prof.Dr.P.B¨oni
2.Univ.Prof.Dr.W.Petry

gereicDiehtunDissdduertatrchiondiewuFrdeakuamlt¨atfu¨r19.09.2005Physikbameid01er.Tec03.2006hnischenangenommUniveren.sit¨atMu¨nchenein-

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English

Inthecurrentworkvariousnewexperimentalmethodsandcomputationprocedures
inthefieldofneutronimagingarepresented.Thesemethodshaveasignificanttechnical
importanceinnon-destructivematerialinvestigations.
Withstroboscopicneutronradiographyperiodicprocessescanbeinvestigatedonasub-
millisecondtimescale.Thisopensgreatopportunitiesforthestudyandthedevelopment
ofcombustionengines.
Energyselectivetimeofflightneutronradiographyatneutronspallationsourcesuses
theenergydependenceoftheneutroncrosssectiontodistinguishbetweenmaterials.The
energyresolutionofthistechniqueisverygoodandallowstheidentificationofspecific
ials.rmateSoftwaretoolsforneutronradiographydataevaluationanddatavisualizationwere
programmed:calibrationalgorithms,imagedeconvolutionprocedures,toolsforimage
assessment,agraphicaluserinterfaceforfastdatainspectionandmanybatchprocessing
routinesforlargeneutronradiographyimageseries.
Thedevelopedmethodsandsoftwaretoolsareinuseattheneutronradiographyand
tomographyfacilitiesatnewresearchreactorFRM-IIinMunich,Germany.

enfassungusammZ

hDeutsc

IndervorliegendenArbeitwerdenverschiedeneneueexperimentelleMethodenund
RechenverfahrenausdemGebietderRadiographieundTomographiemitNeutronen
vorgestellt.DieseDurchstrahlungsverfahrengewinnenzunehmendanBedeutungfu¨rdie
zerst¨orungsfreiePru¨fungvonneuenMaterialien.
MitderstroboskopischenNeutronenradiographie-Methodek¨onnenperiodische
ProzesseaufeinerSubmillisekunden-Zeitskalauntersuchtwerden.Daser¨offnetviele
verheißungsvolleM¨oglichkeitenf¨urdasStudiumunddieWeiterentwicklungvonVerbren-
nungsmotoren.
Dieenergieaufgel¨osteFlugzeit-NeutronenradiographieanNeutronen-
Spallationsquellenn¨utztdieEnergieabh¨angigkeitderSchw¨achungskoeffizientenaus,um
zwischenverschiedenenMaterialienzuunterschieden.DurchdiehoheEnergieau߬osung
dieserMethodewirddasgezielteSuchennachbestimmtenMaterialienineinem
unbekanntenObjektm¨oglich.
Softwarewerkzeugef¨urdieAuswertungundVisualisierungvonNeutronenradiographie-
Datenwurdenprogrammiert:Evaluierungsalgorithmen,ProgrammezurEntfaltungder
Bildunsch¨arfeundzurKorrekturvonArtefakten,einegraphischeBenutzeroberfl¨achef¨ur
dieschnelleDateninspektion,AlgorithmenzurBestimmungderBildqualit¨atsowieRouti-
nenf¨urdieStapelverarbeitungvongroßenBildserien.
DieneuenexperimentellenMethodenundSoftwarewerkzeugewerdenanden
Neutronenradiographie-und-tomographieanlagenamneuenForschungsreaktorM¨unchen
FRM-IIeingesetzt.

Contents

1Physicsofneutronimaging2
1.1Exponentialattenuationmodel.........................3
1.2Effectsofneutronscattering...........................4
1.3Effectsoftotalreflection.............................6
1.4Spectraleffectsinneutronimaging.......................7
1.5MonteCarloSimulations.............................10

ductiontroIn

2

2Experimentalsetupforneutronimaging11
2.1Neutronsource..................................11
2.1.1TheneutronradiographyfacilityANTARESatFRM-II.......12
2.2Neutronradiographydetectors.........................14
2.2.1Scintillators................................15
2.2.2Detectoroptics..............................16
2.2.3CCDcameras...............................17
2.2.3.1LCDshutters..........................18
2.2.3.2InterlinetransferCCDs....................19
2.2.3.3CCDswithimageintensifier.................20
2.2.3.4ShutteredCCDs........................21
2.2.4TheNRdetectoratANTARES.....................22
2.3Theobjectforneutronradiographyandtomography.............23
2.4Imagequality...................................26
2.4.1Apracticalexaminationofimagequality...............27

3Dataevaluationandvisualization33
3.1HardandsoftwarefordataanalysisatANTARES..............33
3.2Artefactcorrection................................34
3.2.1Beamfluctuations............................34
3.2.2Gammaspots...............................34
3.2.3Scintillatordegradation.........................35
3.2.4Lensdistortions..............................36
3.2.5NRdeconvolution............................36
3.3Normalization...................................37
3.4ReproducibilityanduncertaintyofaNRimage................38
3.5QuantitativeNR.................................40
3.6NRdatavisualization..............................42
3.6.1Softwaretoolsfordataevaluationandvisualization..........42
3.6.2Visualizingdifferencesbetweenimages.................44
3.6.3Fusingimages...............................46

CONTENTS

vi

3.7Limitationsbythehumaneye..........................47

4Measurements51
4.1StroboscopicNR:Combustionengines.....................51
4.1.1FirstNRofarunningcombustionengine...............52
4.1.2Carcombustionengine..........................54
4.1.3Injectionnozzle..............................57
4.1.4FirstneutronradioscopyofancombustionengineatFRM-II....60
4.2EnergyselectivetimeofflightNR.......................62
4.3QuantitativeNR:acompressortyperefrigerator...............69

ANewapplication:fossilstone

BVisualizationmethod:DifferenceNRofanoilpump

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91

Introduction

whichuNeutronsethepimagingenetrati(NI)onisofaneucollectivtronseteforrmtheforinvnones-tidegationstructivofethetestiningternal(NDTstr)meucturethodsof
anobject.TheuniqueinformationdeliveredbyNeutronRadiography(NR)andNeutron
inTsighomograptintohyhistori(NT)calconandtriarbutcehetoologithcealdevobeljectopmes.ntofhightechproductsandconcedes
appTheliedfirstatNRtheresimearcageshwreaceretortakenFRMinin1940,Garchatingthewithbeginthermalningofandthesoon80’swiththefasmtnethoeudtronwsas.
Withtheuseoflarge2DdetectorsandincreasingcomputingpowertheNImethodsreally
gotestablished.InthelastyearsnewmethodslikeenergyselectiveNR,phasecontrast
NRandmanynewareasofapplicationsopenedup.Highfluxneutronsourcesanda
growinginterestfromindustryandsciencepushedtheactivitiesinthefieldandgavenew
opportunitiesformethodicalimprovements.InthelastfiveyearseightdiplomaandPhD
thesesaboutNIappeared.
Thisworkisdedicatedtonewexperimentalmethodsfortimeresolvedneutronimaging
andmethodsforquantitativedataanalysis.Itconsistsoffivechapters:
attenChapuationter1modstartsel.FwithorathewiderprincipundleersandtanthdinegphofysicsneutofronNRimandagingpresdenevtsiationtheesxpfonromentithale
simplemodellikeneutronscattering,totalreflection,effectsduetothebeamgeometry
andspectraleffectsarediscussed.
faciliThetiesfexporenrieumentrontalsimagingetupofareaaNIvailfacilitable:yisThtreeatedANTinARESchaptefacilitr2.ywAitththaecoldFRM-IneutItwrono
spectrumandtheNECTARfacilitywithafastfissionspectrum.TheANTARESfacility
ispresentedanddescribedfocussingonthebeam,thedetectorandpossibleobjectsof
.estigationvinAmajorpartofthisworkconsistsofnewandpowerfultechniquesforquantitative
evaluationandvisualizationofNRdata(chapter3).Allimportantstepsoftheevaluation
proceWitdurehinarethisdewscrorkibtedwoandnewtheexpesoftriwmareentalm”Neutrethooneydsew”erefordevviseulopedalizationandisapplexpiedlainined.prac-
timeticalofmeasflighutremNR.enInts:chtheapterstrob4boscothopticechneutrniquesonarimeagiintngrodtecucehdniqanduethandeexptheerenimeerngyts,secarlectriedive
outatneutronimagingfacilitiesinEurope,aredescribedandtheirresultsarediscussed.

1erChapt

Physicsofneutronimaging

TheobjectofinvestigationisplacedinawelldefinedneutronbeamI0(x,y)anda2D
pgraposithyionsimageensitiv(1.1).edeteThisctorshadorecordswimtheagetrconansmtaiinstteindforrmadiatationionabinoutensitttheyIin(tex,rynal),sthteructurradio-e
oftheobject.

Figure1.1:Principleofneutronradiography
Forneutrontomography,aseriesofNRimagesfromdifferentdirectionsaremeasured
byrotatingtheobject.Fromtheimagesstackthecomplete3Dvolumeoftheobjectis
reconstructed.Adetailedmathematicaldescriptionofthetomographicreconstructioncan
befoundin[Kak88,0].Thegreylevelsofeachvolumeelement(voxel)correspondtothe
attenuationcoefficientofthatelement’smaterial.Inthiswaymaterialsdifferinginthe
neutronattenuationcoefficientscanbedistinguishedandtheindividualcomponentsofa
multicompositeobjectcanbeseparated.
NeutronimagingiscomplementarytootherNDTmethodsandoftenpermitsanonde-
structiveanalysiswhenothermethodsfail.CharacteristicforNIistheuniqueability
topenetratelargemetallicobjectsandatthesametimethesensitivityforhydrogenous
materials.Inthefollowingsomeexamplesoftypicalapplicationsarelisted:
•penetrationbehaviourofwaterinsoil,wood,stone,concrete,textilesanddevel