Neutron Scattering

tails. This reflection curve leads alter folding to a much sharper resolution curve .
Experimental resolution curves of single-single and triple-triple reflections are shown in
Fig .8 .10 . One clearly see the effect of multiple reflections .
8 .4. Reflectometer
Investigations of surface properties by surface reflection of neutrons or X-rays is a relatively
new technique and is presently very active field in research . In Fig . 8 .11 the specular
Figure 8 .11 :
Traces ofneutrons and diagram ofmomentum ofspecular refection
reflection of neutrons at a surface is shown and in Fig . 8 .12 a reflectometer for neutrons has
been schematically depicted . Similarly to the pin-hole SANS instrument in Fig .8 .2 the
divergency of the monochromatic neutron primaiy beam is determined by two apertures . In
this example the monochromatic neutron beam is determined by a single crystal within the
neutron guides . A linear position detector measures the reflected neutrons . Specular reflection
as shown in Fig . 8 .11 is defmed by the saine incoming and outgoing angle. In this case the (Q
vector has an orientation perpendicular to the surface and only heterogeneities in direction
perpendicular to the surface e .g . parallel te, Q are measured. An example is shown in Fig . 8 .13
giving the reflection profile of a Nickel metallic film coated on glass . In this case one
measures the heterogeneities formed between Nickel and glass and in addition the surface
roughness between Nickel and vacuum according to thé différent values of thé cohérent
scattering length densities . The intensity profile shows total reflection at small angles and then
at larger angles strongly decreases with periodic oscillations . From this profile one can
determine thickness and roughness ofthé metallic film.
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