The double crystal diffractometer (DCD) at the Geesthacht Neutron Facility
(GeNF) is equipped with triple-bounce channel-cut perfect Si(111) crystals.
In this way the intrinsic background of DCD, i.e. given by the rocking-cur
ve wings, has been decreased dramatically. Its former dependence on the sca
ttering vector q of q(-2) was changed to q(-6). An observed deviation from
the q(-6) behaviour is possibly attributed to neutrons propagating and diff
racting inside the walls of the channel-cut crystals. In order to reduce th
is parasitic intensity and for further improvement of DCD with respect to h
igher sensitivity to weak sample scattering quintuple-bounce side grooved c
hannel-cut crystals have been used. The change in the rocking curves withou
t and with inserting cadmium in the grooves of the walls is pointed out. Th
e efficiency of DCD is shown in the case of neutron scattering from Latex s
pheres with radii of about 2200 nm. (C) 2000 Elsevier Science B.V. All righ
ts reserved.