DESIGN OF A PHOSWICH WELL DETECTOR FOR RADIOXENON MONITORING
The network of monitoring stations established through the Comprehensive Nuclear-Test-Ban Treaty includes systems to detect radioactive xenon released into the atmosphere from nuclear weapons testing. One such monitoring system is the Automated Radio-xenon Sampler/Analyzer (ARSA) developed at Pacific Northwest National Laboratory. For high sensitivity, the ARSA system currently uses a complex arrangement of separate beta and gamma detectors to detect beta-gamma coincidences from characteristic radioxenon isotopes in small samples of xenon extracted from large volumes of air. The coincidence measurement is very sensitive, but the large number of detectors and photomultiplier tubes requires careful calibration. A simplified approach is to use a single phoswich detector, consisting of optically coupled plastic and CsI scintillators. In the phoswich detector, most beta particles are absorbed in the plastic scintillator and most gamma rays are absorbed in the CsI, and pulse shape analysis of the detector signal is used to detect coincidences. As only a single detector and electronics readout channel is used, the complexity of the system is greatly reduced. Previous studies with a planar detector have shown that the technique can clearly separate beta only, gamma only and coincidence events, does not degrade the energy resolution, and has an error rate for detecting coincidences of less than 0.1%. In this paper, we will present the design of a phoswich well detector, consisting of a 1'' diameter plastic cell enclosed in a 3'' CsI crystal. Several variations of the well detector geometry have been studied using Monte Carlo modeling and evaluated for detection efficiency, effects on energy resolution, and ease of manufacturing. One prototype detector has been built and we will present here some preliminary experimental results characterizing the detector in terms of energy resolution and its ability to separate beta only, gamma only, and coincidence events.
- Research Organization:
- Pacific Northwest National Laboratory (PNNL), Richland, WA (US)
- Sponsoring Organization:
- USDOE
- DOE Contract Number:
- AC05-76RL01830
- OSTI ID:
- 891751
- Report Number(s):
- PNWD-SA-7501
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
ARSA
BETA PARTICLES
CALIBRATION
DETECTION
ENERGY RESOLUTION
GEOMETRY
MANUFACTURING
MONITORING
NUCLEAR EXPLOSIONS
NUCLEAR WEAPONS
PHOSPHORS
PHOTOMULTIPLIERS
PLASTIC SCINTILLATORS
PLASTICS
SENSITIVITY
SIMULATION
TESTING
XENON
beta-gamma coincidences
radioactive xenon