D22 - State of the Art
Roland P. May Institut Max von Laue - Paul Langevin, F-38042 Grenoble Cedex 9
SANS is produced by heterogeneities in matter (that can be as well defined as identical viruses in aqueous solution). If these are randomly oriented, every atom pair contributes a sin (Qd) / (Qd) term to the scattering of a sample, where d is the distance between the two atoms of the pair, and Q the momentum transfer, Q = (4π/λ) sin Θ, with 2Θ, the full scattering angle and λ, the wavelength.
Inhomogeneities of sizes larger than atomic distances (10 to 1000 Å) produce scattering patterns with interesting Q ranges 1/D < Q < 10/D, if D is the dimension of the inhomogeneities. The scattering angle 2Θ corresponding to the upper Q limit for D=100 Å is about 9.1 ° for neutrons of 10 Å wavelength.
In most cases, the sample and/or the sample environment are rather bulky. Therefore, SANS instruments usually have to be large themselves in order to yield the desired resolution. Small SANS instruments can only serve a very limited number of applications. For reasons of intensity, a relatively large beam divergence, i.e. a beam cross-section larger than the sample size is accepted as well as wavelength resolutions Δλ/λ of up to about 20 %.
Discovered by Chadwick in 1932 Rest mass
mn = 1.6749543(86) x 10 -24 g
= 1.008665012(37) u
| Temperature dependence of the wavelength
λ(T) [nm] = h / (3m n kT)1/2 = 2.5159 / T1/2
λ(293 K) = 0.147 nm
| Electric charge
q n = - (1.5 ± 2.2 ) x 10 -20 e
| Life time
t = λ 1/2 / ln 2 = 925 ± 11 s
| Magnetic moment
µn = -1.04187564(26) x 10 -3 µ B
= -1.91304308(54) µN
| Frequency
nn = 1.978x10 12 [s -1 ] / λ [nm]
| Speed
v n = h / (m n λ) = 395.6 [m/s] / λ [nm]
| Spin 1/2
|
Total reflection: Ultra-cold neutrons, neutron guides
To top
1983: Proposal (R.P. May, R. Oberthür, P.A. Timmins and A.F.Wright)
1987 (September): Final proposal (R.P. May, M. Thomas) endorsed by Instrument Subcommittee
1989 (December): Delivery of detector tube and collimation by ABT (SIGRI)
1992 (December): Delivery of detector by CERCA (after 24 months)
1995 (February): First tests after reactor overhaul: first users in April
1996 (April): Start of permanent operation after repair of detector
To top
To top
To top
"Classical" pin-hole small-angle scattering instrument
Wavelength selection- DORNIER velocity selector 25 cm long, 28 300 rpm, resolution 10% (fwhm), 4.6 < l < 42 Å for 0 ° tilt
Collimation system- guide cross-section 55 x 40 mm
- 8 drums of lengths varying as a geometical series to yield free flight paths of 1.4 to 17.6 m
- three positions: guide in / apertures (/ optical elements)
- 3 attenuators and 4 round apertures (5, 10, 20, 30 mm diameter), computer controlled
- manually remotely controlled aperture at 19.1 m from sample
To top
- 3He, 2 bars; sensitive surface: 0.96 m x 0.96 m
- 16 K pixels of 0.75 x 0.75 cm
- minimal distance 1.35 m, maximal distance 18 m
- can be translated by half its width, i.e. 50 cm
- can be rotated around its vertical axis (25 °)
- Q-range: 0.7x10-3 Å-1< Q < 1 Å -1
- Qmax/Qmin up to 50, typically 20 with offset, 10 without
To top
- table for mounting equipment in air, e.g. sample changer, shear apparatus
- vessel ("cloche") for working in vacuum
- "orange" cryostats with support permitting direct-beam and reference measurements
- remotely controlled heating/cooling bath (about -10 / +80 °C)
To top
To top
To top
To top
A robot arm for manipulating radioactive (and other) samples
 - ISEL automation
To top
P. Schurtenberger et al. (1998) J. Mol. Biol. 275, 123-132
To top
S. Rycroft and R.J. Stewart (Univ. Reading)
The small-angle neutron-scattering from SiO2 precipitates in a single crystal of silicon which has been heat treated for 500 hours at 600°C; the neutron beam was incident along a <100> direction. The central cross arises from the cushion shaped SiO2 precipitates lying on (100) planes with their edges along <110> directions.
To top
Homogeneous nucleation and growth of oil droplets studied by time-resolved small-angle neutron-scattering
S.U. Egelhaaf (ILL), P. Schurtenberger (ETH Zürich), J. Morris, U. Olsson, H. Wennerström (Lund University)
| 
| 
| Figure 1: Oligodisperse oil-in- water microemulsion droplets are quenched into a two phase area. At final equi- librium, smaller droplets coexist with an excess oil phase that nucleates at a few of the initial droplets which subsequently grow (t > 0), allowing the majority of droplets to decrease in size. This growth phase proceeds with a constant number of large drops (t >> 0).
| Figure 2: Sequence of scattering curves from a time-resolved small-angle neutron-scattering experiment recorded during the nucleation and growth of an excess oil phase from oil-in-water microemulsion droplets. For clarity only every second measurement is shown. As an example the scattering curve obtained at t = 3150 s is added as an inset.
| Figure 3: Time-dependence of the radius of gyration Rg,big as obtained from a Guinier fit. Also shown is the power law behaviour expected for a classical Ostwald ripening process.
|
To top
Jörg Holzinger and Roland May (ILL), Manfred Rößle, Elena Manakova and Hermann Heumann (MPI für Biochemie)
To top
Helium Bubble Growth in a Martensitic Steel for Fusion Reactors
| 
| 
| Fig. 1 (above): Transmission electron micrograph of He bubbles after implantation of 400 appm He at 250 °C (from the work of Bertsch, 1997).
| Fig. 2: Nuclear plus magnetic cross sections of reference and implanted samples for 250 °C (full circles), 825 °C (empty circles), and 975 °C (squares).
| Fig. 3: He-bubble volume distributions (a.u. proportional to bubble volume per unit volume vs. bubble size in Å) obtained from the data of Fig. 2: 250 °C (dotted), 825 ° C (dash-dot), and 975 °C (solid).
|
Our results complete the information available from TEM confirming that a uniform bubble distribution produced by low temperature implantation evolves into a bimodal one, with a population of large bubbles growing when the post-implantation annealing temperature is increased.
To top
Real-time SANS- The high flux allows us to perform real-time experiments
- A much faster detector is needed to work correctly at large Q
Polarization & polarization analysis- Polarized neutrons were used by Neumann et al.
- Werner Heil is interested in developing a 3He spin filter
Spin contrast variation- Oliver Zimmer is adapting a polarized target station
- A test experiment to look at the sizes and the time behaviour of polarized regions in polymers and proteins is planned
Time-of-flight SANS- Space for three chopper systems exists in the design of D22
To top
Design
| Detector
| Electronics
| Hall d'essais
| Mechanics
| Neutron distribution | Organisation | Programming | Technicians | Klaus Gobrecht
John Hayter
Roland May
Radulf Oberthür
Peter Timmins
Michel Thomas
Werner Wagner
Albert Wright
| Roger Chung
Michel Gamon
Bruno Guérard
Jean Jacobé
Anton Oed
André Rambaud
Jochen Uckelmann
| Antony Burton
Frédéric Descamps
Reinhard Klesse
Jacques Munnier
Jacques Ratel
Franck Rey
J.-Antoine Vidal-Garcia
| Claude Gomez
Marc Locatelli
Anthony Pascaud
Émile Stropiano
Pierre Thomas
| Tony Billington
J.-François Carliez
Luc Didier
Guy Gobert
Michel Goursaud
Erwin Hetzler
Jacques Loppé
Philippe Malbert
| Alain Beynet
Peter Suttling Jean-Rémy Villard | Jean-Claude Faudou Marie-Claude Filhol Bernard Guérra Walther Kaiser | Alain Barthélémy
Franck Cécillon Ron Ghosh Georges Messoumian Didier Richard
Michel Roure Helga Schwab Odile Tillier Klaus Wotschack
| Michel Bonnaud David Bowyer
Régis Gay Pierre George |
and many others...
To top
To top
|
Legal notice