  Fast neutrons are a large background to measurements of gamma-rays emitted
from excited nuclei, such that detectors which can efficiently distinguish
between the two are essential. In this paper we describe the separation of
gamma-rays from neutrons with the pulse shape information of the CsI(Tl)
scintillator, using a fast neutron beam and several gamma-ray sources. We find
that a figure of merit optimized for this separation takes on large and stable
values (nearly 4) between 5 and 10 MeV of electron equivalent deposited energy,
the region of most interest to the study of nuclear de-excitation gamma-rays.
Accordingly this work demonstrates the ability of CsI(Tl) scintillators to
reject neutron backgrounds to gamma-ray measurements at these energies.
