Neutron Scattering

L= (1) ( k ) a e -(k/k T ) 2 Ak
(8 .3)
27c k T k
for neutrons with wave vector k, the irradiated area of the sample F, and the divergency of the
primary beam described by the space angle AS2 . The luminosity L is determined by the total
Sample
AS4, A;,/a,
Figure 8 .1 : Traces ofneutrons in real- und reciprocal space
thermal flux of the neutrons 1), the temperature of the moderator (h/2n) Z kT/2m=k,T and
the resolution of wave length distribution according to Ak/k and determined by the
monochromator. The scattered intensity in a detector element with space angle AS2D and
scattering angle 20 or scattering vector Q respectively is given as
(0; Q) -AS2D (8 .4)
Al, (o ; Q)=Al o -D. T .
dE
with sample thickness D and diminution coefficient T ofthe primary intensity (transmission) .
The macroscopic scattering cross section dE/M is the experimental result and is usually
given in absolute units [1/cm] .
8 .3 . Small Angle Scattering with Neutrons
The method of small angle scattering (SANS) is a broadly used tool in research. There are
three different SANS techniques : The pin-hole SANS, the double crystal diffractometer, and
the focusing SANS . The First two types of instruments are being used in our laboratory in
Jülich, and a first focusing SANS instrument is presently built and will start operation in our
laboratory within the next year.
8-2