DEVELOPMENT OF AIRBORNE SURVEILLANCE INSTRUMENTATION.
Abstract
A gamma ray detector was constructed using an inorganic scintillator, CsI(T1), that is viewed by three photomultiplier (PM) tubes. The phosphor is encased in a plastic fluor so that the PM tube array also detects scintillations in the fluor. The detector forms a phoswich assembly (Rev. Sci. Inst. 23:414-417 (1952)), permitting pulse shape discrimination against charged particle reactions occurring within it. External circuitry rejects single signals from the fluor, and fluor/phosphor coincident signals. The unit approaches 100% rejection effectiveness in preventing charged-particle reactions in the detector from introducing signals into the measurement circuitry. Gamma ray losses resulting from gamma-fluor reactions are less than 9% of the total recorded gamma activity in the main CsI(T1) detector for energies below 1.4 Mev. The detector incorporates a small inset-well crystal lying on the central axis, that is optically separated from the CsI; the ratio of inset-well count rate to main crystal count rate provides a directionality parameter defining source position with respect to crystal axis. The detector shows an energy response linearity within the limitations of the analyzer used in the measurements, + or - 1/2%. The resolution for Cs-137 gamma rays exhibited by the assembly is 15.4%. Gamma ray spectral data can be collected with the charged particle rejection feature in operation. (Author)
Document Details
- Document Type
- Technical Report
- Publication Date
- Feb 01, 1966
- Accession Number
- AD0630866
Entities
People
- Harold A. Lamonds
- John E. Hand
Organizations
- EG&G