  To achieve the physics goals of future Linear Colliders, it is important that
electron and positron beams are polarized. The positron source planned for the
International Linear Collider (ILC) is based on a helical undulator system and
can deliver a polarised beam with positron polarization of 60%. To ensure that
no significant polarization is lost during the transport of the electron and
positron beams from the source to the interaction region, spin tracking has to
be included in all transport elements which can contribute to a loss of
polarization. These are the positron source, the damping ring, the spin
rotators, the main linac and the beam delivery system. In particular, the
dynamics of the polarized positron beam is required to be investigated. The
results of positron spin tracking and depolarization study at the
Positron-Linac-To-Ring (PLTR) beamline are presented.
