  Geometric-phase-induced false electric dipole moment (EDM) signals, resulting
from interference between magnetic field gradients and particle motion in
electric fields, have been studied extensively in the literature, especially
for neutron EDM experiments utilizing stored ultracold neutrons and
co-magnetometer atoms. Previous studies have considered particle motion in the
transverse plane perpendicular to the direction of the applied electric and
magnetic fields. We show, via Monte Carlo studies, that motion along the field
direction can impact the magnitude of this false EDM signal if the wall
surfaces are rough such that the wall collisions can be modeled as diffuse,
with the results dependent on the size of the storage cell's dimension along
the field direction.
