The NNSA experimental
setup consists of two segmented Clover detectors and two Planar detectors all of them Compton
Suppressed. The detector array is deployed on the NSSA area.
Each Clover detector consists of four individual crystals sharing a common cryostat. Each crystal is electronically
segmented into two halves, and has an individual efficiency of 25% relative to a 3-inch by 3-inch NaI detector.
By minimizing the dead layer between the adjacent crystals, the signals from all four crystals may be added together
to obtain the total pulse height for an incident gamma ray that scatters from one crystal to one or more of the
other three crystals. This so called add-back mode increases the photo efficiency of a Clover detector from about
100% to more than 150% for Co-60 lines, and provides excellent efficiency for detection of high-energy gamma rays.
When operated in the add-back mode, a single Clover detector has a photopeak efficiency of 0.2% for detection of
1.33 MeV gamma rays. Furthermore, since the segmented Ge crystals have an effective width of 2 cm, the Doppler
broadening resulting from is minimized. The peak-to-total ratio of the Compton-suppressed clover detectors,
when operated in add-back mode, is approx. 0.55 for Co-60. The four individual crystals of a Clover detector
may also be used as a polarimeter.
The NNSA experimental
setup consists of two segmented Clover detectors and two Planar detectors all of them Compton
Suppressed. The detector array is deployed on the NSSA area.
Each Clover detector consists of four individual crystals sharing a common cryostat. Each crystal is electronically
segmented into two halves, and has an individual efficiency of 25% relative to a 3-inch by 3-inch NaI detector.
By minimizing the dead layer between the adjacent crystals, the signals from all four crystals may be added together
to obtain the total pulse height for an incident gamma ray that scatters from one crystal to one or more of the
other three crystals. This so called add-back mode increases the photo efficiency of a Clover detector from about
100% to more than 150% for Co-60 lines, and provides excellent efficiency for detection of high-energy gamma rays.
When operated in the add-back mode, a single Clover detector has a photopeak efficiency of 0.2% for detection of
1.33 MeV gamma rays. Furthermore, since the segmented Ge crystals have an effective width of 2 cm, the Doppler
broadening resulting from is minimized. The peak-to-total ratio of the Compton-suppressed clover detectors,
when operated in add-back mode, is approx. 0.55 for Co-60. The four individual crystals of a Clover detector
may also be used as a polarimeter.
