[Halld-cal] Radiation hard shashlyk calorimeters

[Eugene Chudakov]

FYI: options for the radiation hard FCAL insert.

We need about 200 radiation hard modules at the center of the FCAL.

The current plan is to use radiation hard lead glass.

We are also considering shashlyk modules of the same size, 
which may provide some advantages with respect to lead glass:

a) Better energy resolution. The best resolution was obtained
    (see the 1-st reference)
    with 0.275mm Pb/1.5mm Plastic plates: 2.8%/sqrt(E)+1.3%
    which is about twice better than the resolution of rad.hard
    lead glass detectors.

    A coarser sampling 1.5mm Pb/4 mm plastic, as in PHENIX
    (3-rd reference) lead to 5.9%/sqrt(E)+0.8%. A comparable
    resolution of 5.5%/sqrt(E) was obtained with the GAMS modules
    38x38mm**2 (see the attached photo). The helix-like fibers
    arrangement removes the position dependence of the response.
    The Santa Maria group is going to use such modules
    in Hall B.

b) Radiation hardness up to 1 Mrad, depending on the plastic used.

c) 30-50% cheaper than lead glass

There are groups that might be willing to manufacture 
such modules for us.

http://www.slac.stanford.edu/spires/find/hep/www?irn=7976135

http://www.slac.stanford.edu/spires/find/hep/www?irn=7400306

http://www.slac.stanford.edu/spires/find/hep/www?irn=5662001

http://www.slac.stanford.edu/spires/find/hep/www?irn=8035881

Eugene
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