Technische Universität München> Technische Universität MünchenHelmholtz-Zentrum Geesthacht> Helmholtz-Zentrum GeesthachtForschungszentrum Jülich> Forschungszentrum Jülich
Logo

MLZ (eng)

Lichtenbergstr.1
85748 Garching

KWS-2

Small angle scattering diffractometer

KWS-2 scheme KWS-2 scheme

KWS-2 [1] represents a classical pinhole SANS instrument where, combining the pinhole mode using different neutron wavelengths and detection distances with the focusing mode using MgF2 lenses, a wide Q-range, between 1 × 10-4 and 0.5 Å-1, can be explored (fig. 1). It is dedicated to high intensity / wide-Q investigation of mesoscopic structures and structural changes due to rapid kinetic processes in soft condensed matter, chemistry and biology. The high neutron flux, comparable with that of the world leading SANS instruments, which is supplied by the neutron delivery system (cold source, selector, guides) [2,3] and the possibility to use large sample area using focusing lenses, enable high intensity and time-resolved studies. On demand, the instrument resolution can be tuned using the double-disc chopper with adjustable opening slit, which allows the variation of the wavelength spread between 2 and 20 % (fig. 2). This offers a high flexibility in optimizing the instrument performance towards improved characterization of structural details and accurate beam characteristics (avoid the gravity and chromatic effects while using the lenses).

[1] A. Radulescu, et al., J. Phys. Conf. Series 351, 012026 (2012)
[2] A. Radulescu and A. Ioffe, Nucl. Inst. Meth. A, 586, 55 (2008)
[3] A. Radulescu, et al., Nucl. Inst. Meth. A 689, 1 (2012)

Typical Applications
  • Colloids
  • Polymer blends, diblock copolymers
  • Nanocomposites
  • Microemulsions, complex fluids, micelles
  • Membranes, films; in-situ adsorption–desorption / humidifying – drying phenomena
  • Kinetics of demixing, formation, aggregation
  • Shear induced ordering of complex fluids
  • Shear induced micelle deformation, rubber network deformation, nanocomposite ordering
  • Protein structure and folding/unfolding
  • Pressure dependence of phase diagrams, fluctuations, molecular interactions
  • In-situ crystallization
  • Semi-crystalline polymer films and solutions

Typical application relate to fast structural changes of micellar systems (formation, transformation or chain exchange at equilibrium) or polymer crystallization which are investigated by time-resolved SANS in the second or sub-second (up to 50 ms) regimes. For example, the fast structure evolution in polymer clathrates with small guest molecules and the diffusion of guests in the crystalline region can be understood by monitoring the time evolution of the reflection due to crystalline lamellae (fig. 3).

Sample Environment
  • Rheometer shear sandwich
  • Rheowis-fluid rheometer (max. shear rate 10000 s-1)
  • Anton-Paar fluid rheometer
  • Stopped flow cell
  • Sample holders: 9 horizontal x 3 vertical (temperature controlled) for standard Hellma cells 404.000-QX, and 110-QX
  • Oil & water thermostats (typical 10 °C … 100 °C)
  • Electric thermostat (RT … 200 °C)
  • 8-positions thermostated (Peltier) sample holder (-40 °C … 150 °C)
  • Magnet (1.5 T, vertical)
  • Cryostat with sapphire windows
  • High temperature furnace
  • Pressure cells (500 bar, 2000 bar, 5000 bar)
  • Humidity chamber, 5 % … 95 % for 10 °C … 60 °C
Technical Data

Overall performance

  • Q = 0.0001..0.5 Å-1 (0.9 Å-1, mid 2013)
  • Maximal flux: 2 × 108 n cm-2 s-1
  • Typical flux: 1.3 × 107 n cm-2 s-1
  • (collimation 8 m, 30 x 30 mm², λ = 7 Å)

Velocity selector

Astrium, Δλ/λ = 20 %, λ = 4.5 Å – 20 Å; 3 Å (2014)

Chopper

tunable Δλ/λ: 20 % – 2 % (TOF analysis)

Active apertures

2 m, 4 m, 8 m, 14 m, 20 m, sample position

Aperture sizes

rectangular 1 x 1 mm2 – 50 x 50 mm2

Neutron lenses

MgF2, diameter 50 mm, curvature 20 mm
Packs with 4, 6,16 lenses

Polarizer

transmission, P > 95 % for λ > 4.5 Å

Sample stage

XYZθ translational-rotational stage + craddle
Accuracy better than 0.01°, 0.01 mm

Detector 1

  • Detection range: continuous 1 m – 20 m
  • 6Li-Scintillator 1 mm thickness + photomultiplier
  • Efficiency better than 95 %
  • Active area 60cm x 60cm
  • Spatial resolution 5.25 x 5.25 mm2, 128 × 128 channels
  • Max. countrate 0.6 MHz (τdead = 0.64 μs)

Detector 2 (high res.)

  • Spatial resolution 0.45 x 0.45 mm2
  • Active area: Ø = 8.7 cm
  • 6Li-Scintillator 1 mm thickness
  • Fixed position: 17 m after sample position

Instrument Scientists

Dr. Aurel Radulescu
Phone: +49.(0)89.289.10712
E-Mail:

Dr. Noemi Kinga Szekely
Phone: +49.(0)89.289.10739
E-Mail:

Dr. Marie-Sousai Appavou
Phone: +49.(0)89.289.10747
E-Mail:

KWS-2
Phone: +49.(0)89.289.14326 /.14873

Operated by

JCNS

Gallery

Scattering patterns
Scattering patterns

Figure 1: Scattering patterns from silica and polystyrene particles in solution measured in the pinhole and high-resolution (focusing lenses) modes (fits include the form factor and the structure factor of the particles and the instrumental resolution).

Measurements at KWS-2
Measurements at KWS-2

Figure 2: Measurements at KWS-2 with variable resolution on polystyrene latex particles (samples – courtesy of M.Hellsing and A.Rennie, Uppsala University) and silver behenate; the green lines indicate the fit (including instrumental resolution).

Time evolution
Time evolution

Figure 3: Time evolution of SANS intensity profile and integral intensity of crystalline reflection caused by change in contrast due to exchange from d-benzol to h-benzol in syndiotactic-polystyrene / benzol clathrates (F. Kaneko, Osaka University and A. Radulescu, JCNS)

KWS-2
KWS-2

Technische Universität München> Technische Universität MünchenHelmholtz-Zentrum Geesthacht> Helmholtz-Zentrum GeesthachtForschungszentrum Jülich> Forschungszentrum Jülich