The proper surface treatment of the each
of the modules as it affects the light output and the light collection
uniformity along the longitudinal axis of the crystal has been investigated.
Different wrapping materials have been tested for maximum light output and
minimum non-uniformity. One of the crystals has been studied in beam and with
cosmic rays using the various surface treatments. These studies have resulted
in a convergence upon the following wrapping method: three layers of teflon
thick) plus one layer of aluminized mylar () on the lateral
surface with back paper on the front face. Prior to the wrapping, each crystal
is polished using a mixture of aluminium oxide power and ethylene
glycol. However, other surface treatments are currently under investigation. In
addition, a cosmic ray tomography system has been designed to measure the
light collection non-uniformity throughout the entire volume of each module. In
particular, this method will reveal the regions of impurities and imperfections
where the scintillation light is absorbed. For each of the crystals which
eventually will make up the calorimeter, the non-uniformity must be .
Once the crystals have been tested for F/T and their dimensions checked, they
are wrapped as described above and passed on to the tomography system. The
description of the tomography apparatus and some of its results will be
presented in a subsequent chapter.