Transcript Comparison between Different Methods of SANS Data

Students:
Carmen Breazu, Univ. of Craiova, Romania
Bogdan Guster, Univ. of Bucharest, Romania
Horia Pasca, Univ. Babes-Bolyai, Cluj-Napoca, Romania
Simina Rebegea, Univ. A.I.Cuza, Jassy, Romania
Sabina Simon, Univ. of Bucharest, Romania
Claudia Teodorescu-Soare, Univ. A.I. Cuza, Jassy, Romania
Project Coordinator: Dr. A.I. Kuklin
JINR Summer Student Practice, 13 – 29 July 2011, Dubna
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Small Angle Neutron Scattering is a method used to investigate the
properties of different materials by scattered neutrons at small angles.
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Some methods of investigation, like Small Angle X-ray Scattering (SAXS) or
Scanning Electron Microscopy, are limited in providing information about
structure of matter.
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The advantages that SANS presents, due to the neutrons’ properties are:
◦ Contrast variation method
◦ Interaction with nuclei
◦ Deep penetration
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In a SANS experiment, the differential scattering cross section (dΣ/dΩ) is
measured as a function of the momentum transfer:
Q  4 sin  / 2

-
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λ is the neutron wavelength
θ is the scattering angle between the direction of the transmitted and scattered beams
The dimension of a probe is D = 2π/Q
The range of Q (scattering vector) is 0.001÷1 Å-1
BIOLOGY:
- proteins
- viruses
- lipid aggregates
- emulsificators
CHEMISTRY:
- polymers
- precipitates
- surfactants
- colloids
- gels
Materials science:
- alloys
- glasses
- composites
- porous systems
- grained materials
- ceramics
- powders
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Sizes, spatial correlations and shapes of particles, agglomerates, pores and
fractals in crystalline and in amorphous states as well as in solution on a
length scale ranging from 1 nm up to several hundred nanometers
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Phase transitions
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Degree of polydispersity
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Aggregation numbers
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Molecular weight
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Geometric peculiarities
1. Two reflectors
2. Zone of reactor with moderator
3. Chopper
4. First collimator
5. Vacuum tube
6. Second collimator
7. Thermostat
8. Samples table
9. Goniometer
10-11. Vn-standard
12. Ring-wire detector
13. Position-sensitive detector "Volga”
14. Direct beam detector.
YuMO SANS Instrument
Frank Laboratory of Neutron Physics
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Verifying the spherical shell-like structure of apoferritin with SANS
method of investigation
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Determine the parameters of the structure:
◦ Radius of gyration
◦ Inner and outer radii
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Use of different programs (Fitter, “Primus” from ATSAS pocket of
programs, Origin) in order to compare the results
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ATSAS pocket of programs:
◦
Primus: performs the manipulations with experimental small-angle scattering
data files such as: averaging, subtraction, merging, extrapolation to zero
concentration and curve fitting and evaluates the integral parameters from Guinier
and Porod plots such as radius of gyration (for globular, flat and rod-type
particles), Porod's volume, zero intensity and molecular weight
◦ Gnom: is an indirect transform program for small-angle scattering data
processing. It reads in one-dimensional scattering curves (possibly smeared with
instrumental distortions) and evaluates the particle distance distribution
function P(r) (for monodisperse systems) or the size distribution function D(R) (for
polydisperse systems
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FITTER 1.0.1
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ORIGIN 8.0
Distribution function obtained
with GNOM
Guinier approximation for
a globular particle:
Rg  47.2  1.19 Å
tg  1002.62
tg 
Rg2
3
Rg  54.83  6.83 Å
Rth  51.63 Å
Model: SANS Spherical shell
R1 =60.70± 0.78 Å
R2 =36.60 ±1.15 Å
I (q)  ( R13  R23 )  2[ R13 (qR1)  R23 (qR2 )]2
 sint  t cos t 
 (t )  9

3


t
2
t  qR
2
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From the experimental data gathered from the YuMO SANS Instrument we
obtained the experimental curves;
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Using Primus and Origin we determined the radius of gyration from the
apoferritin and compared them, obtaining similar results;
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Successfully modeled the experimental plot with Fitter, thus obtaining the
inner and outer radii for our sample;
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The overlap between analytical function and experimental fit shows us that
the values of radii determined are correct
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Apoferritin has a spherical shell-like structure
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L.A. Feigin, D I. Svergun, Structure Analysis by X-Ray and Neutron
Scattering
Roger Pynn, Neutron Scattering: A Primer
A.G. Soloviev, A.V. Stadnik, A.H. Islamov, A.I. Kuklin, Fitter. The package for
fitting a chosen theoretical multi-parameter function through a set of data
points. application to experimental data of the YuMO spectrometer
M. Balasoiu, M.L. Craus, J. Plestil, V. Haramus, R. Erhan, M. Lozovan,
A.I. Kuklin, I. Bica, Microstructure of magnetite doped elastomers
investigated by SAXS and SANS
P.V. Konarev, V.V. Volkov, A.V. Sokolova, M.H.J. Koch and D. I. Svergun
(2003). PRIMUS - a Windows-PC based system for small-angle scattering
data analysis. J Appl Cryst. 36, 1277-1282
http://flnp.jinr.ru/135/
http://flnp.jinr.ru/476/
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The group would like to thank the members of the Frank Laboratory of
Nuclear Physics and the YuMO SANS team for all their support and
especially our supervisor Dr. A.I.KUKLIN and PhD. students L. ANGHEL
and R. ERHAN for their guidance and patience.

Thanks to Prof. Dr. Gh. ADAM and Dr. S. ADAM for their good advices
during the Summer Practice.
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We would also like to extend our regards to the organizer of the Summer
Student Practice and all members of the JINR involved with this project.