Neutron Source - FRM II - Technische Universität München

KWS-3 very small angle scattering diffractometer
Entrance Slit
r E
δQ = k ·r E
L
2π
(k = )
λ
Description
KWS-3 is a very small angle neutron scattering experiment
running on the focusing mirror principle
with a wave vector transfer resolution between 10 -4
and 10 -3 Å -1 , bridging a gap between Bonse-Hart
and pinhole cameras. After the transfer into the
guide hall of the FRM II neutron source in Garching
a major upgrade became necessary, with the aim
to make proper use of the enhanced neutron flux,
which is larger by a factor of 7. Especially the
neutron mirror was refurbished with a new 65 Cucoating.
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 at FRM II. After mirror
refurbishment and optical alignment the upgrade
activities are going on at the end of the dedicated
neutron guide.
The principle of this instrument is a one-to-one
image of an entrance aperture onto a 2D positionsensitive
detector by neutron reflection from a
double-focusing elliptical mirror. It permits to perform
SANS studies with a scattering wave vector
resolution between 10 -4 and 10 -3 Å -1 with considerable
intensity advantages over conventional
pinhole-SANS and Double Crystal Diffractometers.
Therefore it perfectly bridges the “Q-gap” between
U-SANS and SANS: Very Small Angle Scattering
(V-SANS).
Mirror Sample
λ = 12 Å
k = 0.5 Å -1
r E = 2 mm
L = 10m
L
Detector
δQ = 10 -4 Å -1
Figure 1: Principle of KWS-3 - superior flux of focusing optics in the resolution regime at very low
Q ≤ 10 -2 Å -1 compared to pinhole geometry. Length scales up to 1 µm are accessible.