> The radiation hardness of the crystals from this vendor should be investigated, in particular in 
> view of using the new calorimeter for other experiments in Hall D.
> The central blocks of the existing lead-glass calorimeters are expected to degrade 
> significantly in a few years of running. The new technical problem to be solved is 
> a stronger magnetic field in the photodetector area, which may require a different 
> photodetector or an extra magnetic shielding

The original idea is to replace the inner part of the Hall-D FCAL with
about a factor of 10 more radiation resistant PbWO crystals. The hybrid 
calorimeter would be beneficial for many experiments in Hall-D. 
Replacing the inner part of the FCAL due to the lead-glass degradation
may anyway be required by the time the PbWO crystal insert is constructed.

The radiation hardness of PWO crystals provided by Chineese ceramic institute, 
yype II crystals, is being intensively tested by JLab HPS collaborators [] 
indicating (acceptably) high quality of crystals produced in China.

The final decision on  photo detectos to be used in the calorimeter will
be based on optimazing the photodetector cost and performance. The hybrid
(PbWO / lead-glass) calorimeter will be operated under the nominal solinoid
magnet field. The preliminary studies of the magnetic field which we have 
performed for the Primex PMTs indicate, that the single clad mu metal shield 
with the thickness of 500 um would reduce the longitudinal and the transverse 
components of the field to the level below 0.4 Gauss and 0.03 Gauss, that 
seems to be acceptable. Further detailed studies on improving shielding
will be performed in the future. Using APDs