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The Use of Large Lithium-Drifted, Germanium Diodes for Gamma-Ray Spectral Measurements at Balloon AltitudesA series of balloon-borne experiments has been initiated at the Oak Ridge National Laboratory (ORNL) in cooperation with the Space Sciences Laboratory of the NASA G. C. Marshall Space Flight Center to determine the feasibility of using large (greater than 20 cc) lithium-drifted, germanium diodes to investigate the spectrum of atmospheric gamma rays (60 keV < E < 1.5 MeV) at altitudes corresponding to a few grams per cm (sup 2) residual atmosphere. The results of these measurements will also provide a basis for designing an appropriate shield for a multi-diode, highly directional gamma-ray spectrometer for use in astrophysical measurements. Two flights were accomplished during 1967 using the same two diodes and basic instrument package. Both flights were launched at the NCAR Scientific Balloon Flight Base, Palestine, Texas, and attained a float altitude of 117, 000 ft. The measured atmospheric gamma-ray spectrum shows at least one distinct line at 511 keV (annihilation radiation) superimposed on a continuous distribution of gamma rays attributable to both energy-degraded gamma rays and brems-strahlung photons. A second diode, encased in a passive shield of plastic and lead, shows the expected lines resulting from both neutron inelastic scattering and capture in the germanium. Data acquisition was accomplished on an event-by-event basis through the use of 512-channel, on-board ADC and word-generator circuits and a ground-based, on-line telemetry decoder. The decoder makes it possible to store the data in the memory of a modified pulse-height analyzer simultaneously with storage on magnetic tape. This provides a real-time visual observation of the data as it is accumulated and greatly facilitates preflight calibrations.
Document ID
20000014162
Acquisition Source
Marshall Space Flight Center
Document Type
Conference Paper
Authors
Chapman, G. T.
(Oak Ridge National Lab. TN United States)
Cumby, R. P.
(Oak Ridge National Lab. TN United States)
Gibbons, J. H.
(Oak Ridge National Lab. TN United States)
Macklin, R. L.
(Oak Ridge National Lab. TN United States)
Nutt, R.
(Oak Ridge National Lab. TN United States)
Packer, H. W.
(NASA Marshall Space Flight Center Huntsville, AL United States)
Date Acquired
August 19, 2013
Publication Date
December 1, 1968
Publication Information
Publication: Proceedings: Fifth AFCRL Scientific Balloon Symposium
Subject Category
Space Radiation
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.
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