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The Bismuth Germanate (BGO) detectors provide spectral coverage
from about 150 keV to 30 MeV. BGO is a high-density material
that provides good sensitivity over this difficult energy
range. The energy resolution of the 12.7 cm by 12.7 cm
cylindrical BGO crystal will be 14% at 661 keV and 4% at 10 MeV
and there will be significant efficiency overlapping the lower
energy range of the LAT. Each BGO detector is coupled to 2 PMTs
on opposite sides, whose outputs are summed, each with its own
high-voltage control. This design allows a homogeneous light
collection over the detector volume and provides redundancy
should one of the PMT?s fail or degrades. The BGO detectors are
positioned on opposite sides of the LAT, providing nearly full
sky coverage.
[Source: NASA]
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