Abstract
The energy spectra observed in a CsI crystal in the 20 keV-2 MeV range, due to the decay of radioactive isotopes produced in the crystal by bombardment with 155 MeV protons, are presented as a function of time after irradiation.
It is shown that the large number of decay products produced by spallation can account for these spectra and that these spectra are in quantitative agreement with the predictions of a semi-empirical formula due to Rudstam, which gives the numbers of different isotopes produced. This formula is used to predict the spallation that would occur in such a crystal on board a satellite due to cosmic rays and passages through the South Atlantic Anomaly. Inspection shows that the spallation produced in the latter case is well approximated by that at 155 MeV. Hence the experimental results are used to explain previously observed background rates and to predict the background rates that would occur in the U.K.5 X-ray telescope of Imperial College. Using the Rudstam formula an estimate of cosmic ray induced background is also made.
The relative importance of activity resulting from neutron interactions (atmospheric albedo and spacecraft secondaries) is considered.
It is suggested that the Rudstam formula provides a general method of predicting induced radio-activity in satellite materials and that observed breaks in the diffuse cosmic X-ray spectrum could be due to inadequate allowance for this source of background.
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References
Dennis, B. R.: 1970, Private Communication.
Dudziak, W. F., Kleinecke, D. D., and Kostigen, T. J.: 1963, ‘Graphic Displays of Geomagnetic Geometry’, RM 63 TMP-2, DASA 1372, General Electric Company
Ebeoglu, D. B., Wainio, K. M., More, K., and Tiffany, O. L.: 1966, ‘Monte Carlo Calculations Radionuclide Production in Iron Targets bombarded with 400 MeV Protons’,J. Geophys. Res. 71, 1445.
Elliot, H.: 1965, ‘Some Cosmic Ray and Radiation Belt Observations based on Data from the Anton 302 G.M. Counter in Ariel I’, inRadiation trapped in the Earth's Magnetic Field (ed. by B. M. McCormac), D. Reidel Publishing Company, Dordrecht-Holland, p. 76.
Funk, H., and Rowe, M. W.: 1967, ‘Spallation yield of Xenon from 730 MeV Proton Irradiation of Barium’, Earth Planet. Sci. Letters2, 215.
Lingenfelter, R. E.: 1963, ‘The Cosmic Ray Neutron Leakage Flux’,J. Geophys. Res. 68, 5633.
Peterson, L. E.: 1965, ‘Radioactivity induced in Sodium Iodide by Trapped Protons’,J. Geophys. Res. 70, 1762.
Peterson, L. E.: 1970, ‘An SKY survey Experiment for 0.3–10 MeV γ-Ray sources for HEAO-A’, U.C.S.D., 3674.
Rudstam, G.: 1966, ‘Systematics of Spallation Yields’,Z. Naturforsch. 21 a, 1027.
Schwartz, D. A.: 1969, ‘The Spatial Distribution of the Diffuse Component of Cosmic X-ray’, Thesis, U.C.S.D.
Strominger, D., Hollander, J. M., and Seaborg, G. T.: 1958, ‘Table of Isotopes’,Rev. Mod. Phys. 30, 585.
Vette, J. I.: 1966, ‘Models of the Trapped Radiation Environment, Volume I: Inner Zone Protons and Electrons’,NASA SP-3024.
Waddington, C. J.: 1969, ‘The Fragmentation of Cosmic Ray Nuclei in Interstellar Hydrogen’, Univ. of Minnesota Preprint.
Webber, W. R.: 1967, ‘The Spectrum and Charge Composition of the Primary Cosmic Radiation’,Handbuch der Physik,46, 181.
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Dyer, C.S., Morfill, G.E. Contribution to the background rate of a satellite X-ray detector by spallation products in a caesium iodide crystal. Astrophys Space Sci 14, 243–258 (1971). https://doi.org/10.1007/BF00649205
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DOI: https://doi.org/10.1007/BF00649205