Neutron Scattering

a large solid angle with polarizers in front of the detectors an enormous amount (6000)
of magnetic multi-layers had to be produced . A 7r-flipper (Vlezei-type wich a Brookhaven
correction coil) is used in the incident beam .
The following example [14] of a measurement at D7 demonstrates the capabilities of
such an instrument : the dynamic structure factor of liquid sodium, is separated into
the coherent and (spin-)incoherent parts . The quasi-elastic incoherent scattering gives
information about the single particle motion in space and time, while coherent quasielastic
scattering is related to collective relaxations of the ensemble . The measurements
shown in Fig . 4 .15 have been measured on the D7 instrument in time-of-flight spectroscopy,
while the presentation is given in the coordinates of energy and momentum transfer .
15
15
10
3 5
3
49.1
1 2 3 1 0 1 2 3
Seattering Vector [X-1 ]
Scattering Vector [V]
Figure 4 .15 : Contour plots of (a) the (spin-) incoherent scattering and (b) coherent scattering
from liquid sodium at T = 840 K over the plane of energy and momentum transfer
as separated by polarization analysis on D7 . The incoherent scattering is related to the
single particle motion ; the coherent scattering is related to the collective motion . [14] .