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85748 Garching


Small angle scattering diffractometer


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 x 10-4 and 0.5 Å-1 can be explored.

The instrument 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 [2].

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) [3, 4], and the possibility to use large sample area using focussing 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 [5], which allows the variation of the wavelength spread between 2 and 20%. This offers a high flexibility in optimising the instrument performance towards improved characterisation of structural details and accurate beam characteristics (avoid the gravity and chromatic effects while using the lenses).

[1] Radulescu, A. et al., J. Phys. Conf. Series 351, 012026 (2012)
[2] A. Radulescu et al., J. Vis. Exp. 118, e54639 (2016), KWS-2 film
[3] Radulescu, A ., Ioffe, A., Nucl. Inst. Meth. A, 586 , 55 (2008)
[4] Radulescu, A. et al., Nucl. Inst. Meth. A 689, 1 (2012)
[5] A. Radulescu et al., J. Appl. Cryst. 48, 1860 (2015)

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

Self-assembly of block-copolymers in micellar structures is a widely studied topic at KWS-2. The properties of block-copolymer micelles tuned by changing e.g. solvent quality, temperature, solvent selectivity, block copolymer composition, and molecular weight are investigated thoroughly benefiting from the adjustable instrumental resolution between 2 and 20%.

Another kind of typical application relate to fast structural changes of micellar systems (formation, transformation or chain exchange at equilibrium) or polymer crystallisation which are investigated by time-resolved SANS in the second or sub-second (up to 50 ms) regimes. More recently, the determination and control of the morphological parameters of biocompatible gels and amphiphiles became an important topic of study stimulated by the demands from nanomedicine related to the design of new functional drug delivery vehicles.

Sample Environment
  • Anton-Paar fluid rheometer
  • Stopped flow cell
  • Sample holders: 9 horizontal x 3 vertical (temperature controlled) for standard Hellma cells
  • Oil & water thermostats (typical 10 …100°C)
  • 8-positions thermostated (Peltier) sample holder (-40°C … 150°C)
  • Magnet (1.5 T, vertical)
  • Cryostat with sapphire windows
  • Pressure cells (500 bar, 5000 bar)
  • Humidity chamber, 5% … 95% for 10°C … 60°C

Complementary in-situ techniques (optional at sample aperture, see instrument drawing)

  • FT-IR spectroscopy
  • DLS & SLS
  • 3He spin analyzer (SEOP)

Technical Data

Overall performance

  • Q = 0.0001… 1 Å-1
  • Maximal flux: 2 x 108 n cm-2 s-1
  • Typical flux: 2.5 x 107 n cm-2 s-1 (collimation 8 m, 50 x 50 mm², λ = 5 Å)

Velocity selector

  • Astrium, Δλ/λ = 10% standard) or 20% tilted selector), λ = 3… 20 Å


  • 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


  • Transmission, P > 95% for λ > 4.5Å

Sample stage

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

Detector 1

  • Detection range: continuous 1 – 20 m
  • 3He tubes array
  • active area ~0.9 m2
  • count rate for no deadtime >2 MHz
  • resolution = < 8 mm
  • stability of pixel response ~0.1%
  • efficiency 85% for 5 Å

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

Dr. Christian Lang
Telefon: +49 (0)89 289-10739

Dr. Marie-Sousai Appavou
Phone: +49 (0)89 289-10747

Phone: +49 (0)89 289-14326 /-14873

Operated by



Find the latest publications regarding KWS-2 in our publication database iMPULSE:

Citation of the instrument

Heinz Maier-Leibnitz Zentrum. (2015). KWS-2: Small angle scattering diffractometer. Journal of large-scale research facilities, 1, A29.

For citation please always include the DOI.



Instrument KWS-2 in the Neutron Guide Hall West.

Neutron flux KWS-2 October 2016
Neutron flux KWS-2 October 2016

The neutron flux at the sample position, including the new configuration with short wavelength, which was commissioned in 2016

New 3He detector
New 3He detector

The counting rate and the dead-time of the new [^3]He detector.

Qmax at KWS-2
Qmax at KWS-2

The Qmax reached at KWS-2 by using tilted velocity selector and short neutrons wavelength.

Dynamic Q-range
Dynamic Q-range

The dynamic Q-range for different instrument configurations.


The absolute neutron flux at the sample position.


The available range of momentum transfer Q for a selection of instrument configurations (the experimental data are described by model
function convoluted with the instrument resolution).

Time evolution
Time evolution

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).


KWS2_10%_wavelength_resolution_jpg © ja

MLZ is a cooperation between:

Technische Universität München> Technische Universität MünchenHelmholtz-Zentrum Geesthacht> Helmholtz-Zentrum GeesthachtForschungszentrum Jülich> Forschungszentrum Jülich
MLZ App (Android)
MLZ App> MLZ App