ebook img

NCNR 2001 PDF

80 Pages·2002·7.4 MB·English
Save to my drive
Quick download
Download
Most books are stored in the elastic cloud where traffic is expensive. For this reason, we have a limit on daily download.

Preview NCNR 2001

JST SP 971 NAT'L j^*"" NlST j jj*! ^|*|ll 1 PUBL!CATiC;f;S NIST Q^^f^fTf^i, Neutron Research Accomplishments and Opportunities Nisr National Institute of Standards and Technology TechnologyAdministration QC U.S. Department of Commerce 100 U57 March 2002 no.977 2002 OntheCover Thetwo photosdramatizethedevelopmentoftheNISTCenterforNeutron Research overa 12-yearperiod. ThelowerphotoshowstheCold Neutron Guide Hall before installation ofequipment. Theupperpicture,takenfromapproximatelythesame vantage point, ispackedwith7guidetubesserving 13 instrumentstations. See pages2-3fora layoutand briefdescriptionoftheinstruments. Pages4-5 provide aselected pictorial historyoftheCenter. (Topphotoby L.A. Shuman.) NCNR 2001 NIST Center for Neutron Research Accomplishments and Opportunities NIST Special Publication 977 J. Michael Rowe, Director Ronald L. Cappelletti, Editor Linda K. Clutter, Assistant Editor March 2002 U.S. DEPARTMENT OF COMMERCE Donald L. Evans, Secretary TechnologyAdministration Phillip J. Bond, Under Secretary forTechnology National Institute of Standards and Technology Arden L. Bement, Jr., Director DISCLAIMER Certaincommercialentities,equipment,ormaterialsmaybeidentifiedinthis documentinordertodescribeanexperimentalprocedureorconceptadequately. Suchidentificationisnotintendedtoimplyrecommendationorendorsementby theNational InstituteofStandardsandTechnology,norisitintendedtoimplythat theentities,materials,orequipmentarenecessarilythebestavailableforthe purpose. National InstituteofStandardsandTechnologySpecial Publication977 Natl. Inst. Stand.Technol. Spec. Publ. 977, 76pages(March2002) C0DEN;NSPUE2 U.S. GOVERNMENTPRINTINGOFFICE-WASHINGTON:2001 ForsalebytheSuperintendentofDocuments, U.S. Government PrintingOffice — — Internet: bookstore.gpo.gov Phone: (202) 512-1800 Fax: (202) 512-2250 Mail: StopSSORWashington, DC20402-0001 8 Contents Foreword iv Introduction 1 NISTCenterforNeutron Research Layout 2 Chronology ofthe NCNR in Photographs 4 Research Highlights Measurementofthe Free Neutron Lifetime 6 ETS-4: IVlaxweli'sZeolite 8 MeasuringStressReliefin ElectronBeamWeldJointsofSuperalloys 10 EXPGUI: SmoothingthePathto PowderCrystallography 12 Neutron DiffractionContributestoImprovingtheFatigueLifeofBridges 14 CapillaryNeutron LensforPromptGammaActivation Micro-Analysis 16 GiantAnharmonicityand Electron-PhononMediatedSuperconductivityin MgB^at39K 1 Polaron FormationandColossalMagnetoresistanceinManganites 20 FerromagnetismandSpontaneousVortexFormationinSuperconducting ErNi^B^C 22 StructureofLocalSpin ExcitationsinaGeometrically FrustratedAntiferromagnet 24 Pressure-Induced PhaseTransitionofC^^EjMicelles 26 ProbingtheStructureofAerosol Nanodroplets 28 NanoporousUltra-LowDielectricConstantMaterials 30 NeutronReflectivityStudiesofSurfactantsatElectrodeSurfaces 32 MagneticSemiconductorSuperlattices 34 PinpointingChiralStructuresWith Front/BackPolarizedNeutron Reflectometry 36 TheNatureofVibrationalSofteningin a-Uranium 38 NativeandPartiallyUnfoldedProteins: NeutronInelasticScatteringandSimulations 40 AtomicMotionsinConfined PolymerFilms 42 Tuningthe PropertiesofCarbon NanotubesbyDeformation 44 ServingtheScientificandTechnological Communities 46 The NCNR User Program 46 TheCenterforHigh Resolution NeutronScattering 46 SummerSchoolon MethodsandApplicationsofNeutronSpectroscopy 47 Collaborations 47 IndependentPrograms 48 Operations 50 Instrumentation Developments 51 TheAdvancedCold NeutronSource 51 DevelopmentofanAir-Padand FloorSystemforNew NeutronSpectrometers 52 Developmentofan IntercalatedGraphiteMonochromator 52 NCNR ComputerandSoftware Environment 53 Sample EnvironmentTeam 55 Publications 56 Instrumentsand Contacts 72 Contacts InsideBackCover NIST Center for Neutron Research iii Foreword - La,^.-:^, ...,. . ..... .. -... : . _ AS this is being written, we havejust begun a three- tor drums and focusing devices. A new cold neutron triple month shutdown during which we will, among other axis spectrometer is currently entering detailed design phase changes, install a next-generation liquid hydrogen cold as ajoint construction project with Johns Hopkins Univer- source, which will increase cold neutron intensities by sity (partially funded by the NSF). In orderto create more almost a factor oftwo. This is an excellent example ofthe research space in the guide hall, a new building for our necessary operating philosophy for any facility - improve- technical support activities is nearing completion. In re- ment and change are the only constants. During the past sponse to many recommendations, we have significantly year, we have had many changes in reactor systems, in strengthened our sample environment support and our data instrumentation, in staff, and in science, all ofwhich are acquisition and analysis computing effort, adding additional aimed at continuing the development ofthe NIST Center for staffand refocusing efforts. The number ofresearch partici- Neutron Research as a first rate neutron facility. pants continues to grow, surpassing all ofour expectations. Anew cooling tower, which is specially designed to Overall, we are moving forward on many fronts to reduce the visible vaporplume during winter months, as well strengthen ourresearch facility operations efforts, in orderto as to provide full cooling ability for the next 20 years, has better serve our customers. been constructed. It will be connected into the reactor And, as always, the scientific results are the true secondary systems during the shutdown that hasjust started. measure ofsuccess, and the highlights that form the largest A new analysis ofmajorreactor systems has been initiated portion ofthis report comprise an excellent set ofexamples using the most modem tools as part ofpreparing the applica- ofthe exciting outputs ofthe facility. I hope that you enjoy tion for a license extension through 2024. Many other reading them as much as I did. improvements, ranging from instrumentation renewal to better provision for maintenance to improved electrical distribution, are under way as part ofthe preparation forre- licensing. In spite ofthe shutdown thatjust started, the reactor has once again performed admirably, operating for 240 days during the fiscal year, meeting our scheduled operating time. The three new inelastic scattering instruments, which werejust coming on line last year, are now being fully incorporated into the user program, with encouraging user demand. Thejoint National Science Foundation (NSF)/NIST Center for High Resolution Neutron Scattering is being expanded to include operation ofthese instruments in addition to the prior SANS and triple axis instruments. The thermal neutron upgrade program, which includes two new triple axis spectrometers, an improved filter analyzer spectrometer, and other instruments, is advancing well, with characterization ofmonochromator crystals now complete, and contracts awardedforthe manufacture ofmonochroma- i,' iv Introduction to the NIST Center for Neutron Research (NCNR) Modem technological society is dependent upon process, that provides a stringent test ofnuclear theory; and increasingly sophisticated use ofmaterials with the effects ofvarious external influences such as gravity or attributes dictated by their sub-microscopic structural and magnetic fields on neutrons. dynamical properties. A wide range oftechniques provides The NCNR's 20-MW NIST Research Reactor provides knowledge ofthese properties. Scattering probes (for anational user community with facilities, including the example: x-rays, light, electrons, neutrons) are arguably the nation's only internationally competitive cold neutron most important. Ofthese probes, neutrons are perhaps least facility, for all ofthe above types ofmeasurements. There familiar, but they provide important advantages formany are about 35 stations in the reactor and its associated beams types ofmeasurements. that can provide neutrons for experiments. At the present Modem sources provide neutrons moving at speeds time 28 ofthese are in active use, ofwhich 6 provide high comparable to those ofatoms at room temperature, thus neutron flux positions in the reactor for irradiation, and 22 providing the ability to probe dynamical behavior. Neutrons are beam facilities. The following pages show a schematic are also well matched to probe lengths ranging from the layout ofthe facility. More complete descriptions ofinstru- distances between atoms to the size ofbiological orpolymer ments can be found at http://www.ncnr.nist.gov. macromolecules. Neutrons are sensitive to the magnetic These facilities are operated both to serve NIST properties ofatoms and molecules, allowing study ofthe mission needs and as a national facility, with many different underlying magnetic properties ofmaterials. They also modes ofaccess. Some instrumentation was built years ago, scatter differently fromnormal hydrogen atoms than they do and is not suited to general user access; however, time is from heavy hydrogen (deuterium), allowing selective study available for collaborative research. NIST has recently built ofindividual regions ofmolecular systems. Finally, neutrons new instrumentation, and reserves 1/3 ofavailable time for interact weakly with materials, providing the opportunity to mission needs with the balance available to general users. In study samples in different environments more easily (at high other cases, instrumentation was built and is operated by pressures, in shear, in reaction vessels, etc.), and making Participating Research Teams (PRT); PRT members have % them a non-destructive probe. These favorable properties are access to 75 ofavailable time, with the balance available offsetby the weakness ofthe best neutron sources compared to general users. Additionally, NIST and the National to x-ray orelectron sources, and by the large facilities Science Foundation operate the Center for High Resolution required to produce neutrons. As aresult, major neutron Neutron Scattering at the NCNR, with one thermal and five sources are operated as national user facilities to which cold neutron instruments. Forthese facilities, most time is researchers come from all over the United States and abroad available for general users. While most access is forre- to perform small-scale science using the special measure- search, with results that are freely available to the general ment capabilities provided. public, proprietary research can be performed under full cost In addition to scattering, neutrons can be captured by recovery. Each year, about 1600 researchers (persons who nuclei to probe the atomic composition ofmaterials. The participated in experiments at the facility, but did not subsequent characteristic radioactive decays provide "finger- necessarily come here) from all areas ofthe country, from prints" for many atomic nuclei, allowing studies ofenviron- industry, academia, and govemment use the facility for mental samples forpollutants (e.g., heavy metals), character- measurements not otherwise possible. The research covers a ization ofStandard Reference Materials, and other measure- broad spectrum ofdisciplines, including chemistry, physics, ments. There are important areas in physics that can be biology, materials science, and engineering. explored by measuring fundamental neutron behavior. Examples include the lifetime ofthe free neutron, important for the theory ofastrophysics; the neutron beta decay NIST Center for Neutron Research 1 NIST Center for Neutron Research Layout 11 ! i ACold Neutron Depth 3 BT-8 Residual Stress 7 BT-2TripleAxisCrystal 10 NG-7Horizontal Sample i Profiling instrument(not Diffractometeroptimizedfor Spectrometerwithpolarized Reflectometerallows { shown)forquantitativeprofiling depthprofilingofresidualstress beamcapabilityformeasure- reflectivitymeasurementsof ! ofsubsurfaceimpurities in largecomponents. mentofmagneticdynamicsand freesurfaces, liquidvapor ) currentlyatthissitewill be ^ BT-9TripleAxisCrystal structure. interfaces, aswellaspolymer ! movedtoanotherposition. Spectrometerformeasure- 8 BT-4 FilterAnalyzerNeutron coatings. } ShownisaproposedTriple mentsofexcitationsand Spectrometerwithcooled Be/ 11 Neutron Interferometryand ! AxisCold Neutron Crystal structure. Graphitefilteranalyzerfor OpticsStationwith perfect Spectrometerwithdouble | focusingmonochromatorand ^ Thermal Column Averywell- chemicalspectroscopy. siliconinterferometer;vibration | dmueltteicptloerscrtyhsattalcaannalbyezfelre/xibly tuhseerdmaflorizreaddiboegraamphoyf,nteoumtorgornas- 9 BDiTf-f5raPcetrofmeectteCrrySsAtNalSsmall eisxocleapttiioonnsaylsptheamspersotvaibdileistyand j'j configuredforseveralenergies phy,dosimetryandother angleneutronscattering fringevisibility. I! simultaneouslyorforhigh experiments. instrumentformicrostructureon 12 Spin PolarizedTripleAxis j throughputatoneenergy. 6 BT-1 PowderDiffractometer the 10"nmlengthscale, Spectrometer (SPINS)using sponsoredbytheNational cold neutronswithposition BT-7TripleAxisSpectrometer with32detectors; incident Science FoundationandNIST, sensitivedetectorcapabilityfor 'j withfixedincidentenergyfor wavelengthsof0.208nm, partoftheCenterforHigh high resolutionstudies—partof amnedassutrruecmtuernet.sofexcitations 0hi.g1h5e4stnmr,esaolnudti0o.n15of95ndm/,dw=ith (ReCsHoRlNuSti)o.nNeutronScattering CHRNS. ' 8x10". 2 Layout 2001 13 Spin EchoSpectrometer 16 Neutron PliysicsStation 18 Disl<CliopperTOFSpectrom- 21 8m SANSforpolymer offeringneVenergyresolution, acoldneutron beam eterversatiletime-of-flight characterization,sponsoredby baseduponJulichdesign, 150mmX60mm,availablefor spectrometer,withbeam NISTPolymersDivision. sponsoredb-yNISIJulichand fundamentalneutronphysics pulsingandmonochro- 22 VerticalSampleReflectometer ExxonMobil partofCHRNS. experiments. matizationeffectedby7disk instrumentwithpolarization 14 PromptGammaActivation 17 Fermi ChiopperTOFSpec- choppers. Usedforstudiesof analysiscapabilityformeasur- Analysiscoldneutronfluxes trometerahybridtime-of-flight dynamicsincondensedmatter, ing reflectivitiesdownto 10"Mo allowdetectionlimitforH of spectrometerforinelastic including—macromolecular determinesubsurfacestructure. 1 |igto10|ag. Focusedbeams scatteringwithincident systems partofCHRNS. 23 VerticalSampleReflectometer areavailableforprofiling. wavelengthsbetween0.23nm 19 NG-330m SANSformicro- instrumentwithpolarization 15 NG-730m SANSformicro- and0.61 nmchosen byfocusing structuremeasurements analysiscapabilityformeasur- structuremeasurements pyrolyticgraphitecrystals.A sponsoredbytheNational ing reflectivitiesdownto 10"^ simpleFermichopperpulses ScienceFoundationand NIST sponsoredbyNIST, - optimizedforbiological ExxonMobil,andtheUniversity thebeam. partofCHRNS. applications. Itwill havea ofMinnesota. 20 Bacl^scatteringSpectrometer: position-sensitivedetectorfor highintensityinelasticscattering measuringoff-specular instrumentwithenergy reflections. resolution<1 |aeV,forstudies ofmotioninmolecularand — biologicalsystems partof CHRNS. NiST Center for Neutron Research 3 NCNR Chronology of the in Photographs 1966 Fred Shortenand ChuckWareatbeamtubeopening(BT-4) Awaitingcriticality, December7, 1967. Chianti notyetuncorked. during construction in 1966. ConstructionoftheGuideHailoftheColdNeutron Facility RayKammer,TawfikRaby, BobCarter, ErnieAmbler, MikeRowe begins in 1988. (currentNCNRdirector),andJackRush(currentsciencegroup leader)inthecontrol roomasthesourcegoesto20MW in 1984. | GeorgeBalticand MikeRinehartintheGuideHall John BarkermakesadjustmentsasSusan Krueger insertingacold neutronguidetube, ca. 1990. and Min Lin getsettorecordresultsattheNG-7 30mSANS, 1991. 4 Chronology of the NCNR in Photographs

See more

The list of books you might like

Most books are stored in the elastic cloud where traffic is expensive. For this reason, we have a limit on daily download.