  Two types of wedge-shaped CsI(Tl)s were designed to be placed behind the
annular double-sided silicon detectors (ADSSDs) to identify the light charged
particles with the $\Delta E-E$ method. The properties of CsI(Tl)s with
different shapes and sizes, such as energy resolution, light output
non-uniformity and particle identification capability, were compared by using a
$\alpha$-source and a radioactive beam of $^{15}$C. The big-size CsI(Tl) was
finally adopted to form the $\Delta E-E$ telescope due to better properties.
The property differences of these two types of CsI(Tl)s can be interpreted
based on the Geant4 simulation results.
