Downstream of the dump magnet in figure 
on both the 
and 
flight paths are a set of dipoles with horizontal fields
and a superconducting
solenoid. These magnets are used to precess the polarization of the
outgoing neutrons. The primary concern is that the neutron polarimeter can
only measure a polarization if it is transverse to the neutron direction of
motion (
or 
). If one wishes to measure
the longitudinal component of the neutron polarization 
it is necessary to precess that polarization to a measurable state. The
magnets, and in particular the solenoids, are also used to occasionally
flip
the neutron polarization by 
. This, combined with the fact that
the beam polarization is flipped every 
seconds is enough to
cancel out any systematic asymmetries which may exist in the detector.
The dipoles also serve the purpose of sweeping away any charged particles
produced in the target or the surrounding shielding so they will not
interact with the detector downstream.
The
first dipole magnet downstream from the dump magnet on the 
line
is a permanent magnet placed there for safety. Should the dump magnet fail
the entire beam would follow the path of the neutrons and get swept skyward
by the permanent magnet.