Neutron Scattering

Current methods for complete polarization analysis of magnetic neutron scattering are
based on zero-field techniques[9], which impose severe limitations and cannot be applied
on multi-detector or time-of-flight instruments . Recently, a new method for full vector polarization
analysis lias opened new possibilities[18] . Using precessing neutron polarization
on the DNS instrument (Jülich the off diagonal terms of the (3 x 3) polarization matrix
can be determined . It is noteworthy, that polarisation analysis is simultaneously achieved
for all scattering angles and energy transfers, which is of interest for diffuse (inelastic)
magnetic scattering, and also in view of new instruments at spallation sources . This
new method utilises precessing polarisation by operating the flipper in a -F/2-mode . By
varying the magnetic field integral the precessinn angle at the sample is determined, and
scattered neutrons with a finally non-precessing polarisation can be analysed . Fig . 4 .18
shows a simulation of scattering processes changing the incident polarization from P X
into a final polarization P y for different scattering angles . Since the final polarisation is
parallel to the magnetic field the polarisation is adiabatically rotated and guided to the
final polarisation analysers .
pII
0
v
iiiif
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Figure 4 .18 : Simulation of precessing neutron polarisation analysis for scattering processes
with changes in polarisation from P x to Py .
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