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Cosmogenic radioisotopes on LDEF surfacesThe radioisotope Be-7 was discovered in early 1990 on the front surface, and the front surface only, of the LDEF. A working hypothesis is that the isotope, which is known to be mainly produced in the stratosphere by spallation of nitrogen and oxygen nuclei with cosmic ray protons or secondary neutrons, diffuses upward and is absorbed onto metal surfaces of spacecraft. The upward transport must be rapid, that is, its characteristic time scale is similar to, or shorter than, the 53 day half-life of the isotope. It is probably by analogy with meteoritic metal atmospheric chemistry, that the form of the Be at a few 100 km altitude is as the positive ion Be(+) which is efficiently incorporated into the ionic lattice of oxides, such as Al2O3, Cr2O3, Fe2O3, etc., naturally occurring on surfaces of Al and stainless steel. Other radioisotopes of Be, Cl, and C are also produced in the atmosphere, and a search was begun to discover these. Of interest are Be-10 and C-14 for which the production cross sections are well known. The method of analysis is accelerator mass spectrometry. Samples from LDEF clamp plates are being chemically extracted, purified, and prepared for an accelerator run.
Document ID
19920017996
Acquisition Source
Legacy CDMS
Document Type
Conference Paper
Authors
Gregory, J. C.
(Alabama Univ. Huntsville., United States)
Albrecht, A.
(Rutgers Univ. New Brunswick, NJ., United States)
Herzog, G.
(Rutgers Univ. New Brunswick, NJ., United States)
Klein, J.
(Pennsylvania Univ. Philadelphia., United States)
Middleton, R.
(Pennsylvania Univ. Philadelphia., United States)
Date Acquired
September 6, 2013
Publication Date
June 1, 1992
Publication Information
Publication: NASA. Langley Research Center, Second LDEF Post-Retrieval Symposium Abstracts
Subject Category
Atomic And Molecular Physics
Accession Number
92N27239
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.

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