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ScatteringScattering of Neutronsof NeutronsBasicsBasics

Regine Regine WillumeitWillumeitGKSS Research CenterGKSS Research Center

How are neutrons produced?

What are the properties of neutrons?

The concept of contrast variation

Experimental set up of a SANS instrument

Data analysis: what is different to X-rays

1.11.2010: Helmholtz Zentrum Geesthacht Zentrum für Material und Küstenforschung

Fission

200 MeV

n = 2 MeV

Natural abundance 0.71 %

HowHow areare Neutrons Neutrons ProducedProduced??

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ViewView of of thethe FRG1FRG1

HowHow areare Neutrons Neutrons ProducedProduced??ShutShut down in

down in JuneJune 2010

2010

Reactor hall

warm water

Schematic picture of FRG-1

controll center

reactor poolsecond pool

reactor core

first cooling system

Heat exchanger

beryllium reflector

beamlines

experimental hall

second cooling system

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ComparisonComparison Power : Research Power : Research ReactorReactor

enrichment 3.3-3.5 % <20 %

# fuel elements 840 12

therm. power 3690 MW 5 MW

moderator H2O H2O

neutron flux << 1014 n/s cm2 1.4x1014 n/s cm2

type pressure swimming-pool

fuel UO2 U3Si2

Power Research

[Krümmel] [FRG-1]

ILL: = 1.5*1015 n/s cm2 [Prof R. Scherm]

= 1.5*1021 n/s m2

average speed: v = 2000 m/s

density = /v = 6.8*1017 n/m3

comparison air: p=10-7 mbar!

WhatWhat doesdoes thethe fluxflux meanmean??

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Spallation

Particles with high energy hit a target

neutrons come out

HowHow areare Neutrons Neutrons ProducedProduced??

SNSSNS

[H-]Protons

liquid Mercury1 GeV H+

1 Protons -> 20-30 Neutrons

European Spallation Source „ESS-I“

HowHow areare Neutrons Neutrons ProducedProduced??

Three sites were competing: Lund (S), Bilbao (E)

and Debrecen (H)

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European Spallation Source „ESS-I“

HowHow areare Neutrons Neutrons ProducedProduced??

ESS

MAX-Lab

Malmö

ComparisonComparison of Neutron of Neutron SourcesSources

ESS

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CorrelationCorrelation betweenbetween Energy and Wave Energy and Wave LengthLength

pm

pm

Neutron Neutron PropertiesProperties

no charge

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Neutron Neutron PropertiesProperties

magnetic moment

Neutron Neutron PropertiesPropertiesDeep Penetration

deep inside materials or technical components

residual stress, texture, cavities, precipitates, cracks ...

Strong Magnetic Interaction

magnetic surface and bulk structures ...

magnetic structure on atomic scale, domane structures ...

Strong Interaction with H2 and D2

surface and bulk structures, ordered layers, solution ...

Soft matter research: polymers, colloids, biological macromolecules ...

Nuclear Reactions

chemical analysis of more than 50 elements in bulk ...

-Spectrum => nuclear activation analysis

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Neutrons X-Rays

Intensity low high

H-sensitivity high none

Isotope-sensitivity strong none

Heavy elements low high

Spin-sensitivity strong average

Penetration depth high low

Sample size/amount large small

Measurement time long short

Interaction with nuclei electron shell

electron shell

unsystematic Z

Radiation damage none high

To To RememberRemember::

Interaction of Interaction of RadiationRadiation withwith MatterMatter

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Interaction of Interaction of RadiationRadiation withwith MatterMatter

Interaction with electrons

Light scattering

Interaction with electrons

X-ray scattering

Scattering ‘strength’ is proportional to Z

Interaction with electron spin possible

Interaction with nuclei (protons and neutrons)

Neutron scattering

Scattering ‘strength’ does not vary systematically

Interaction with nuclear spin possible

Interaction with electrons and electron spin possible

Atomic Scattering factors / length

H

R.Winter, F. Noll: Methoden der biophysikalischen Chemie, Teubner (1998)

X-Rays

Neutrons

atomic mass / g mol-1

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ComparisonComparisonNeutronNeutron-- and and XX--rayray--scatteringscattering lengthlength

somesome relevant relevant elementselements [10[10--12 12 cm]cm]

n X-ray1H -0.37 0.282H 0.67 0.2812C 0.66 1.6814N 0.94 1.9616O 0.58 2.2431P 0.51 4.232S 0.28 4.4856Fe 0.95 6.72

Neutron Neutron ScatteringScattering LengthLengthof of biologicalbiological relevant relevant elementselements [10[10--12 12 cm]cm]

[F. Sears (1986), H. Glättli und M. Goldmann (1987)]

deuterate whenever possible!

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ContrastContrastVariationVariation

When the monster came, Lola, like the pepperedmoth and the arctic hare, remained motionless and undetected.

Harold of course, was immediately devoured.

TheThe ConceptConcept of of ContrastContrast VariationVariationContrast = Difference of Scattering Length Densities

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Contrast =Difference of

Scattering Length Densities

p(R) = Particle(R) - LM(R)

p(R) = Particle(R) - LM

(R) = Scattering Length Densitiy =Sum of Scattering Length of

all Atoms in a Volume

X-Ray Scattering

Neutron Scattering

Volume Fraction D2O

Scattering Length Density of the Solvent [1010 cm/cm3]

Sca

tter

ing

Len

gth

Den

sit

yo

f th

eS

olu

te[1

010

cm

-2]

Water Sugar

Synaptic Arrangement of the Neuroligin/b-Neurexin Complex Revealedby X-Ray and Neutron Scattering. D. Comoletti et al. Structure 15 (2007) 693–705

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Synaptic Arrangement of the Neuroligin/b-NeurexinComplex Revealed by X-Ray and Neutron Scattering. D. Comoletti et al. Structure 15 (2007) 693–705

Synaptic Arrangement of the Neuroligin/b-Neurexin Complex Revealedby X-Ray and Neutron Scattering. D. Comoletti et al. Structure 15 (2007) 693–705

Imp

ossib

leto

crystallize

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Synaptic Arrangement of the Neuroligin/b-Neurexin Complex Revealedby X-Ray andNeutron Scattering. D. Comoletti et al. Structure 15 (2007) 693–705

Deuterated!

Synaptic Arrangement of the Neuroligin/b-Neurexin Complex Revealedby X-Ray andNeutron Scattering. D. Comoletti et al. Structure 15 (2007) 693–705

Deuterated!

42% D2O

We „see“ the deuterated with neutronsand the whole complex with X-rays

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Synaptic Arrangement of the Neuroligin/b-Neurexin Complex Revealedby X-Ray andNeutron Scattering. D. Comoletti et al. Structure 15 (2007) 693–705

Distance Distribution

Setup of a SANS InstrumentSetup of a SANS Instrument

GKSS

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A A TypicalTypical SANS InstrumentSANS Instrument

Monochromator

Crystal

Selector

29 cm

25 cm

Number of plates: 72thickness [mm]: 0.4twist angle: 48.27°material: carbon fiber in

epoxy with 10B or Gd

MonochromatorsMonochromators: Time of : Time of FlightFlight

t=0 t=x

Chopper

REFSANS@FRM-II

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A A TypicalTypical SANS InstrumentSANS Instrument

Collimation Line

A A TypicalTypical SANS InstrumentSANS Instrument

Collimation Line

Neutron Neutron guidesguidesbased on total reflection

kC 2 b = atoms / cm3

b = scattering length

critical angle: sin c = / b/

Materials c [mrad] c [°] dc [nm]

Al 0.81 0.048 62Ni 1.70 0.10 2958Ni 2.03 0.12 25Fe 1.62 0.095 31Co 0.86 0.051 58glass 1.06 0.062

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A A TypicalTypical SANS InstrumentSANS Instrument

Collimation Line

Sample Position

Detektor

Materials c [mrad] c [°] dc [nm] Al 0.81 0.048 62Ni 1.70 0.10 2958Ni 2.03 0.12 25Fe 1.62 0.095 31Co 0.86 0.051 58glass 1.06 0.062

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Measurements Raw Data [Chaperonin GroEL]

Data Integration

Principle

Beam center

Pixel size

'Mask' measurements

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Data Integration

Correction: cos3()

Solid angle correction

Integration

Q [Å-1]

I tot/ m

onito

r

'pure'

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Measurements Detector response: H2O

Measurements

Detector response

Water (H2O) 1mmVanadiumPlastic

Strong incoherent scatterer

Normalization

Water (H2O) 1mm

Vanadium

Knowledge about the coherent cross section

I(q)norm = I(q) / T

I(q)H2O / T H2O

for all detector pixels

G.D. Wignall, F.S. Bates: Absolute calibration of small angle neutronscattering data. J. Appl. Cryst. (1987) 20, 28-40

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Integration

Q [Å-1]

Nor

mal

ized

I tot/ m

onito

r'divided by water'

SANS-1@FRG-1

10 m 10 m

SANS-2@FRG-1: 2 x 20 mD11@ILL: 2 x 40 m

Rule of thumb: collimation length = sample-detector distance

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SANS-1@FRG-1

10 m 10 m

Neutron guide Collimator

Integration

Q [Å-1]

'with collimation correction'

Nor

mal

ized

I tot/ m

onito

r

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Considerations about Scattering data

Beam profile

Wave length profile

Sample concentration, dark current, backgroudsubtraction (cuvette), dead time corrections

Detektor resolution

Smearing Effects

solid angle correction

We considered so far:

detector response (division by water)

flux reduction by collimation

We still have to consider:

Influences on the measured intensity: Smearing

Detektor resolution

Gauss-distribution WD

I(q) = I(q) WD dqm

Influence on mediumand large q-range

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Finite collimation

Influences on the measured intensity: Smearing

Detektor resolution

I(q) = I(q) WD WC dqm

Gauss-distribution WC

Influence on smallq-range

Finite collimation

Influences on the measured intensity: Smearing

Detektor resolution

Wavelength resolution

I(q) = I(q) WD WC W dqm

Gauss-distribution W

Influence on mediumand large q-range

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Influences on the measured intensity: Smearing

http://www.neutron.anl.gov/ Neutron Scattering Home Pagehttp://pathfinder.neutron-eu.net/idb The Neutron Pathfinderhttp://ess-scandinavia.eu/about-esss ESS Scandinaviahttp://www.ill.fr/ ILL homehttp://www.isis.stfc.ac.uk/ ISIShttp://sni-portal.uni-kiel.de/kfn/ Komitee Forschung mit Neutronen

Argonne National Lab

Thank your foryour Attention!