More information please find in the JCNS Experimental Report 2007/2008.

KWS-3 is the world only very small angle neutron scattering instrument running on the focusing mirror principle. It allows to perform scattering experiments with a wave vector transfer resolution between 10^-4 and 10^-3 Å^-1, bridging a gap between Bonse-Hart and pinhole cameras. The principle of this instrument is a one-to-one image of an entrance aperture onto a 2D position-sensitive detector by neutron reflection from a double-focusing elliptical mirror.



The instrument has considerable intensity advantages over conventional pinhole-SANS and Double Crystal Diffractometers and perfectly bridges the "Q-gap" between U-SANS and very small angle scattering (V-SANS). In addition, a second sample chamber at the distance of 1 m allows the extension of the Q-range up to 3.5 10^-2 Å^-1 giving proper overlap to the Q-range of the other SANS machines KWS-1 and KWS-2 of JCNS at FRM II.

After the transfer of the instrument from Jülich into the neutron guide hall of the FRM II in Garching a major upgrade was performed in order to make proper use of the enhanced neutron flux at the FRM II. Especially the neutron mirror was refurbished with a new ⁶⁵Cu coating (Carl Zeiss Laser Optics GmbH) and the mirror housing was equipped with protecting sapphire windows enabling a vacuum pressure of 10^-3 mbar. In parallel comprehensive upgrade activities in the entire vacuum system (new user-friendly SPS control), the electronic system and programming were performed. Finally conceptual improvements were achieved by implementing a new sample chamber at about 1 m distance. After optical alignment the beam line was commissioned since the reactor cycle of June/July 2009 and is now running in normal user operation.

Applications:

Structural analysis on a length scale up to (beyond) 1 micrometer for numerous materials from physics, chemistry, materials science and life science, like alloys, diluted chemical solutions and membrane systems.

Below the V-SANS (Very Small-Angle Neutron Scattering) measurement of an ordered polymer (PMMA) with a radius of 776 nm is depicted. The spherically shaped polymer particles with a diameter of about 1.5 micro meter causes rings of scattered neutron intensity around the beam centre. The very high scattering intensities caused by the primary beam in the centre of the rings are not depicted on the full scale.

Instrument parameters: Distance sample to detector = 10 m (1 m at second sample position) Wavelength resolution of MgLi Selector Δλ/λ = 0.2 Wavelength λ = 12 Å (24 Å with an order of magnitude less in flux) Size of aperture (focus): 2 x 2 mm2 5 x 5 mm2 optional with a flux 6 times higher but reduced Q-resolution Resolution δQ = 10-4 Å-1 (extension to 4 10-5 Å-1 possible) Neutron flux (focus) = 5000 n/sec = factor 7 compared to Juelich Q-range: 1.6 10-4 - 3.5 10-3 Å-1 at 10 m distance Q-range: 1.6 10-3 - 3.5 10-2 Å-1 at 1 m distance

Image of the 2 mm x 2 mm aperture on the pixel detector with pixel size 0.4 mm