Neutron Imaging and Applications: A Reference for the Imaging Community PDF
Preview Neutron Imaging and Applications: A Reference for the Imaging Community
Neutron Imaging and Applications NeutronScatteringApplicationsandTechniques SeriesEditors: IanS.Anderson AlanJ.Hurd NeutronSciencesDirectorate LujanNeutronScatteringCenteratLANSCE OakRidgeNationalLaboratory LosAlamosNationalLaboratory Building8600,MS6477 POBox1663,MSH805 OakRidge,TN37831 LosAlamos,NM87545 USA USA [email protected] [email protected] RobertL.McGreevy ISIS ScienceandTechnologyFacilitiesCouncil RutherfordAppletonLaboratory HarwellScienceandInnovationCampus Chilton,DidcotOX110QX UK [email protected] NeutronApplicationsinEarth,EnergyandEnvironmentalSciences LiyuanLiang,RomanoRinaldi,andHelmutSchober,eds. ISBN978-0-387-09415-1,2009 NeutronImagingandApplications:AReferencefortheImagingCommunity IanS.Anderson,RobertL.McGreevy,and HassinaZ.Bilheux,eds. ISBN978-0-387-78692-6,2009 Ian S. Anderson Robert L. McGreevy l Hassina Z. Bilheux Editors Neutron Imaging and Applications A Reference for the Imaging Community 1 3 Editors IanS.Anderson RobertL.McGreevy OakRidgeNationalLaboratory RutherfordAppletonLaboratory, OakRidge,TN,USA Oxfordshire,UK [email protected] [email protected] HassinaZ.Bilheux OakRidgeNationalLaboratory OakRidge,TN,USA [email protected] ISBN978-0-387-78692-6 e-ISBN978-0-387-78693-3 DOI10.1007/978-0-387-78693-3 LibraryofCongressControlNumber:2008936128 #SpringerScienceþBusinessMedia,LLC2009 Allrightsreserved.Thisworkmaynotbetranslatedorcopiedinwholeorinpartwithoutthewritten permissionofthepublisher(SpringerScienceþBusinessMedia,LLC,233SpringStreet,NewYork, NY10013,USA),exceptforbriefexcerptsinconnectionwithreviewsorscholarlyanalysis.Usein connectionwithanyformofinformationstorageandretrieval,electronicadaptation,computer software,orbysimilarordissimilarmethodologynowknownorhereafterdevelopedisforbidden. Theuseinthispublicationoftradenames,trademarks,servicemarks,andsimilarterms,evenifthey arenotidentifiedassuch,isnottobetakenasanexpressionofopinionastowhetherornottheyare subjecttoproprietaryrights. Coverillustration:CovergraphicscourtesyofDrJohnKatsaras,NationalResearchCouncil,Chalk RiverLaboratories,andDrTanerYildirim,NISTCenterforNeutronResearch. Printedonacid-freepaper springer.com Preface ThefirstsuccessfulexperimentsinNeutronRadiographywerecarriedout(to ourknowledge)in1935,justafewyearsafterthediscoveryoftheneutron,by H. Kallmann and E. Kuhn using a small neutron generator [1]. Not surprisingly, the field has developed and diversified over the last 70 years so thatneutronimaging,inthebroadsense,isnowroutinelyusedinawiderange of applications. The aim of this book (one of a series on the applications of neutron scattering [2]) is to introduce to the reader, whether novice or experienced researcher, the basic techniques used to image objects using neutron beams and to give a flavor of the vast range of applications where theseimagingcapabilitiesprovideuniqueinsight(Fig.1). Fig.1 Lefttoright:Pressuregaugewithmetalbackplate;firehydrantandtesttubesfilledwithHO 2 andDOimagedwithgamma-rays(top)andneutrons(bottom)[3] 2 v vi Preface Traditionally,‘‘neutronimaging’’isusedtodescribethedirectproductionof imagesbytransmitting abeamofneutrons through anobject ontoadetector (e.g.,film),i.e.,exactlythesameasisdonewithX-raystoimagebrokenbones. An extension of this two-dimensional method (radiography) is to take many images of the same object in different orientations, and then to use the set of imagestoreconstructathree-dimensionalimage(tomography).Althoughthis maystillseem tobe ‘‘direct’’imaging, infact theimageis‘‘re-constructed’’by softwareinacomputerandsophisticatedmathematicalprocessescanbeusedto enhanceparticularfeaturesorgeneratevirtualslicesoftheimagedobject.We refertosuchapproachesas‘‘constructed’’orindirectimagingmethods. Therearemanyotherwaysinwhichvirtualpicturesorimagesofanobjectcanbe renderedfrommoreindirectmeasurements.Ultrasoundimagingofanunbornbaby involvesthereconstructionofanimagefromscatteredsoundwaves.Asthesizeof the object being imaged decreases then simple direct imaging becomes effectively impossible,asthewavelengthoftheradiationbeingusedbecomesofcomparable size.‘‘Indirect’’imagingmethodssuchaselectrondiffractioncanproduceessentially thesame‘‘images’’ofcrystalstructuresasthoseproducedbyanapparently‘‘direct’’ methodsuchastransmissionelectronmicroscopy,andindeeditiscommontouse thecombinationofthesetwotechniquestoenhancetheimages. For example Fig. 2 shows a TEM/STEM image of Si N . The sample 3 4 progressesfromcrystallineatthebottomtoamorphousstructureatthetop.In additionthereisalayeroflanthanumatomsontopofthecrystallinepartofthe sample.Thecrystallinestructureisoverlaidwithaball-and-stickimageobtained bydiffractionfromthecrystal. Directimagingresolvesthecrystalstructurethe same way that diffraction (indirect imaging) does; it does not resolve the amorphous structure, but amorphous structure can be determined by diffraction[4]. Fig.2 ImagecourtesyofDavidCockayne(OxfordUniversity) Preface vii The current extreme example of indirect imaging is probably the reconstruction of three-dimensional images of single nanoparticles from coherentX-raydiffraction. Inthisbookwehaveintentionallytakenabroadviewofneutronimagingto include any process by which a picture or image of an object, or part of an object,can be produced based on theinteractionwitha neutron beam. These methodsandtheirapplicationsinclude (cid:2) Direct imaging methods such as neutron radiography being used to study operatingfuelcells (cid:2) Three-dimensionaltomographicalreconstructionsofmechanicalobjects (cid:2) Theuseofindirectmethods suchasdiffractionorsmall-angle scatteringto imagestrainpatternsinmaterials (cid:2) Indirectimagingoftheshapesofbiologicalmoleculesbyreconstructionfrom small-angleneutronscatteringdata. Clearly,neutronimagingisalesswell-knowntechniquethanX-rayimaging; mostpeopleknowofthesimplemedicalapplicationsofX-rayradiographyand themorerecentextensiontotomography(CATorcomputedaxialtomography scanning). This is largely due to the fact that it is simpler, and less costly, to generate and manipulate high-intensity sources of X rays than of neutrons. Hence theapplications highlightedin thisbook rely heavily on thedistinctive propertiesofneutronbeams,whichallowusefulandoftenuniqueinformation tobederivedfromtheimage. (cid:2) Neutronsareweaklyinteractingneutralparticlesthatpenetratedeeplyinto mostmaterials,sotheycanbeusedtointernallyimagelargeobjects,e.g.,a full-sizeoperatinginternalcombustionengine,non-destructively. (cid:2) Theamountofscatteringorabsorptionofneutronsbyatomicnucleivaries in an apparently random fashion through the periodic table. Hydrogen in particularhasaverylargescatteringcross-section.Neutronscantherefore providegoodcontrastforlightatomsinthepresenceofheavyatoms,e.g., the ‘‘classical’’ neutron image of a rose inside a lead flask (Fig. 3). This makesneutronimaginghighlycomplementarytoX-rayimaging(Fig.1). (cid:2) Theamountofscatteringorabsorptioncanalsovarysignificantlybetween isotopes of the same chemical element; e.g., hydrogen has a very different scattering cross-section from that of its isotope deuterium. The contrast of particular elements/materials in an image can therefore be enhanced by substitutingoneisotopeforanother(Fig.1). (cid:2) ‘‘Thermal’’ neutrons have wavelengths similar to inter-atomic distances, so mechanismssuchasrefractionordiffractioncanbeusedtoenhanceimages ortoproduceindirectimages. (cid:2) Neutrons have a magnetic moment and a magnetic scattering cross-section that is comparable to the nuclear cross-section for many atoms. They can thereforebeusedtoimagemagneticstructures. viii Preface Fig.3 Neutronradiographofaroseinaleadflask[5] Hencetheintrinsicpropertiesofneutronsallowawiderangeofobjectstobe imaged, ranging from massive structures such as helicopter blades to the fine details of crystal structures and passing through the delicate composition of biological organisms and plants. Furthermore, these intrinsic properties pro- vide for an extensive range of contrast enhancement mechanisms including absorption, scattering, diffraction, refraction, magnetic interactions, and, potentially,vibrations.Thesemechanismscanbeusedtodeterminetheelemen- talcompositionsofobjects,whichmayevenbehidden,buried,orencapsulated withinanimpenetrableenvironment.Thepossibilityofstudyingobjectsinsitu, orinrealoperationalenvironments,ispromisingforarangeofindustrialand academicapplications. Neutronimagingtechniqueshaveahugepotentialbutinthepast,applica- tionshavebeenslowtodevelop,mainlybecauseoftheweaknessofthesource Preface ix itself.Eventhemostpowerfulneutronsourcesinexistencetodayhaveasource brightness that is comparable to a simple X-ray tube and many orders of magnitude lower than a third-generation synchrotron X-ray source. Hence, whilesynchrotronX-raysourcesprovidethecapabilityofimagingsinglenano- particleswithnanometerresolution,ordynamicimagesoflargerobjectswith micrometer spatial resolution and microsecond time resolution, neutrons are presentlylimitedtostaticimageswithspatialresolutionsoftheorderoftensof microns, or dynamic images of 100 microns and microsecond exposure times for stroboscopic processes. Neutron imaging of smaller objects can only be achievedindirectly,usingscatteringtechniquesfromanensembleofparticles. Despite these limitations, the following chapters give a flavor of the wide range of applications that presently (or will potentially) benefit from neutron imagingtechniques.Thebookisorganizedintothreemajorsections. Section A provides a comprehensive overview of basic neutron techniques aimedmorespecificallyatanon-specialistaudience.Frequentreferenceismade to the two introductory chapters in the first book of this series [2] by Roger Pynn (Neutron Scattering – a Non-Destructive Microscope for Seeing Inside Matter),andHelmutSchober(NeutronScatteringInstrumentation).Boththese chapters are freely available at www.springerlink.com. In Chapter 1 Kenneth Herwig summarizes the essential neutron properties and techniques which are relevant to the majority of neutron imaging applications. Masatoshi Arai and KentCrawfordprovide,inChapter2,anexcellentsurveyofthedifferenttypes and characteristics of neutron sources, including nuclear reactors, high-power spallationsources,andportablegenerators,whicharetypicallyusednowadays forneutronimaging.Althoughthereisconsiderableoverlapintheuseofthese sources,eachtypeofsourcehasspecificadvantagesforcertaintypesofapplica- tions. Due to the low-intrinsic brightness of neutron sources, efficient optical systemsareimperative,soKenAndersen’schapter(Chapter3)presentsthebasic concepts of the neutron optics that are typically used on imaging beam lines. Finallyinthissection,LowellCrow(Chapter4)examinesmodernneutrondetec- tion methods for imaging. The first section reviews neutron capture converters which form the basis for thermal neutron detection, and the following sections examinedetectorsystemswithanemphasisonimagingapplications. SectionBfocusesontheneutronbeamimplementationofsomewell-known imaging techniques. Arthur Heller and Jack Brenizer (Chapter 5) present a summary of the history, methods, and related variations of neutron radio- graphy techniques including a section on the application of standards. Even today,conventionalfilmradiographyremainsthemainstayofhigh-resolution, largefield-of-view,neutronimaging.InChapter6,WolfgangTreimerextends the basic theories and applications to include three-dimensional tomography and introduces some of the newer methods for enhancing contrast such as wavelength dependent (‘‘Bragg edge’’) imaging and small-angle scattering. KennethTobinetal.(Chapter7)provideareviewofneutronimageformation, resolution analysis concepts, and methods for both the design and characterization of radiography systems and conclude with a discussion of x Preface volumetric reconstruction techniques using analytic or iterative computed tomographyalgorithms. The next two chapters describe techniques that depend intrinsically on the wave nature of the neutron. Franz Pfeiffer (Chapter 8) provides a fascinating overviewofneutronphaseimaginganditsnaturalextensiontoneutronphase tomography. This technique offers the potential to image fundamental quan- tummechanicalinteractions.BhaskarSuretal.(Chapter9)showinitialresults fromneutronholographyexperimentsusingboththeinternalandtheexternal sourceapproaches.Althoughinitsinfancy,neutronholographyhasthepoten- tialtoresolvetoatomicresolutionthestructuresofmaterials,whicharedifficult to crystallize. Finally in this section Nikolay Kardjilov et al. (Chapter 10) describe some novel imaging techniques using the magnetic properties of the neutron.Afterdemonstratingthepowerofneutronstoimagemagneticfieldsin and around objects, they go on to describe theoretically some tantalizing but challengingpotentialapplicationsofspincontrastimagingandneutron-based magneticresonanceimaging. Section C provides the reader with an excellent, though non-exhaustive, overview of some specific applications of neutron imaging in diverse fields of research. Muhammad Arif et al. (Chapter 11) describe in situ neutron radio- graphy and tomography studies of operating fuel cells and hydrogen storage systems, undoubtedly a high priority global research field for the foreseeable future, where the ability of neutrons to ‘‘see’’ hydrogen provides essential information to improve the practical chemical and mechanical engineering design. Dayakar Penumadu (Chapter 12) provides an overview of some recent applicationsofneutronimagingmethodstobroadclassesofmaterialsscience andengineeringstudiesincludingmetalcasting,strainimaging,andcharacter- izationofdiscreteparticlesystems. Carla Andreani et al. (Chapter 13) discuss the growing use of neutrons to imageartifactsofinterestinthedomainofculturalheritage.Novelcharacter- izationmethodsallowdeterminationoftheprovenanceofancientobjectsand canshedlightonthemethodsandtoolsusedatthetimeofmanufacture. In Chapter 14 Kenneth Watkin et al. summarize past and recent research effortstoapplyneutronradiographytobiologicalspecimens,intheexpectation thatclinicalandmedicalresearch,aswellasforensicscience,maybenefitfrom advancedneutronimagingmethods. Moving on to prospective techniques for live imaging, Anuj Kapadia describes (in Chapter 15) the development of a tomographic technique that usesneutron inelasticscatterinteractionstoquantitativelyidentifythespatial distributionofelementsinthebody.Thetechnique,calledNeutronStimulated Emission Computed Tomography (NSECT), uses a beam of fast neutrons to excitestableisotopesofelementsinthebodytodeterminetheirconcentration andspatialdistributionwithinthebody.Ithasthepotentialtodiagnoseseveral element-related disorders in humans that are characterized by a change in elementconcentrationinthediseasedtissue.
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