Neutron Scattering

complex sample environments, such as extreme temperatures, magnetic fields, external
pressures, etc . due to its fiedd scattering geometry . The resolution of the time-of-flight
analysis Ot/t depends on the wavelength-dependant pulse structure of the moderator, on the
length of the flight path, and on the scattering angle 20 (a back-scattering geometry is
recommended). As there are normally relatively short wavelengths in the beam, too, also
higher indexed reflections with shorter dhki-values mat' be reached . Some typical technical
data ofthe IIRPD installed at the spallation source ISIS/RAL in England are shown in Fig . 8 .
A special feature of this instrument consists in the vert' long flight path of about 100 m .
6m 9m
choppers
95K liquid
methane moderator
curved guide
Fig . 8 . FIRDP (high-resolution powder diffractometer) at the spallation source ISIS/RAL,
England. A resolution of Ad/d z 4 .10-4 is achieved with a samplc position at 95 m .
6
allI li IlI IIIIIIIIHII1 I IIIII1 ICI I IIIIII II~1!Hi1 1111 0111r
50-
Fig . 9 . Powder diffractogram of bcnzene : (a) section from 0.72 Â