Neutron Scattering

For a ADP-powder diffractometer the measuring time can be reduced substantially by the
simultaneous use ofmany single detectors or of linear multidetector systems .
As an example for a 2-axes diffractometer specially designed for the investigation of
amorphous systems and liquids the 7C2-instrument installed at the hot neutron source of the
ORPHEE-reactor in Saclay (F) is shown in Fig . 7 . Combined with an exchange of
monochromator crystals there are there différent standard wavelengths available : A,(Ge(111))
= 1 .1 A, ;,(Cu(111)) = 0 .7 A, A,(Ge(311)) = 0.57 A. The linear multidetector allows a
continuous intensity measurement over a range in scattering angle of 128° . The angular
resolution of this instrument is limited as there is no collimation in between the sample
position and the detector. But the I (Q I -range is very large . For the shortest wavelength
k(Ge(311)) = 0.57 A the accessible values extend up to (~ ,aX = 2n I H 20 A- ' .
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Fig . 7 . Plan of the 2-axes diffractometer 7C2 at the hot source of the ORPHEE-reactor in
Saclay (F)
In the case of the EDP method a polychromatic white beam is used with the scattering angle
being fixed (20 = const .). The dhkl-values result from the time-of-flight measurement of the
neutron velocities - converted to wavelengths - for the hkl reflections . This technique is
specially suitable for pulsed neutron sources . Moreover, it offers some advantages for
7- 9