Wrapping with protective felt
Module Light Leak testing
While every module from the first batch of production passed the light leak test without any problems, the same was not true for the second batch of production modules. In the second batch, 4 out of 5 of the modules had one or more light leaks. The light leaks were due to damaged Tedlar mostly at the bottom surface edge, and in cases where modules had multiple leaks, the leaks consistently spaced. We tracked the problem to the module transport structure, and how the structure was being tilted to fit in our freight elevator.
We have now improved our procedures for transporting modules, but to insure module protection each modules is now wrapped in a protective black felt. This protective felt will remain individually on each module and will be removed just prior to installation in the TOF frame at JLAB.