NCNR 2001

80 Pages·2002·7.4 MB·English

by  Cappelletti, Ronald L.

JST SP 971
NAT'L
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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: [phone] Fax: [phone]
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