E3: Two-pi Counter Array
This counter array consists of 81 segments of BaF2 Crystal
detectors. A picture of one of the crystals is shown below.
Specifications are as follows:
BaF2 crystals :
75 hexagonaltrapezohedTOns 10 cm long
front faee 6 sides of2.8 cm
6 pentagonaltrapezohedrons 10 cm long
front face 2 sides of2.3 cm
3 sides of 2 .8cm
Front window A 1 of 100 micron-m thick
Distance from the center (target position)
to the window 15 .5 cm
Energy resolution < 12.5% for 137Cs 661-key gamma rays
(time constant 1.5 micro sec)
< 32% for the same gamma rays
(time constant 50 nsec)
Time resolution < 700 psec at FWHM
Background <0.1 Bq/g (226Ra)
Total weight 1000kg
Some crystals can be removed to accommodate other
detectors such as Ge counters.
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