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The Abundances of Ultraheavy Elements in the Cosmic Radiation

Citation

Newport, Brian John (1986) The Abundances of Ultraheavy Elements in the Cosmic Radiation. Dissertation (Ph.D.), California Institute of Technology. http://resolver.caltech.edu/CaltechTHESIS:10092014-143512211

Abstract

Analysis of the data from the Heavy Nuclei Experiment on the HEAO-3 spacecraft has yielded the cosmic ray abundances of odd-even element pairs with atomic number, Z, in the range 33 ≤ Z ≤ 60, and the abundances of broad element groups in the range 62 ≤ Z ≤ 83, relative to iron. These data show that the cosmic ray source composition in this charge range is quite similar to that of the solar system provided an allowance is made for a source fractionation based on first ionization potential. The observations are inconsistent with a source composition which is dominated by either r-process or s-process material, whether or not an allowance is made for first ionization potential. Although the observations do not exclude a source containing the same mixture of r- and s-process material as in the solar system. the data are best fit by a source having an r- to s-process ratio of 1.22+0.25-0.21, relative to the solar system The abundances of secondary elements are consistent with the leaky box model of galactic propagation, implying a pathlength distribution similar to that which explains the abundances of nuclei with Z < 29.

The energy spectra of the even elements in the range 38 ≤ Z ≤ 60 are found to have a deficiency of particles in the range ~1.5 to 3 GeV/amu, compared to iron. This deficiency may result from ionization energy loss in the interstellar medium, and is not predicted by propagation models which ignore such losses. ln addition, the energy spectra of secondary elements are found to be different to those of the primary elements. Such effects are consistent with observations of lighter nuclei, and are in qualitative agreement with galactic propagation models using a rigidity dependent escape length. The energy spectra of secondaries arising from the platinum group are found to be much steeper than those of lower Z. This effect may result from energy dependent fragmentation cross sections.

Item Type:Thesis (Dissertation (Ph.D.))
Subject Keywords:Physics
Degree Grantor:California Institute of Technology
Division:Physics, Mathematics and Astronomy
Major Option:Physics
Thesis Availability:Restricted to Caltech community only
Research Advisor(s):
  • Stone, Edward C.
Group:Space Radiation Laboratory
Thesis Committee:
  • Stone, Edward C. (chair)
  • Frautschi, Steven C.
  • Barnes, Charles A.
  • Newman, Harvey B.
Defense Date:21 May 1986
Funders:
Funding AgencyGrant Number
CaltechUNSPECIFIED
NASANAG8-502
NASANGR05-002-160
NASANAS8-27978
Record Number:CaltechTHESIS:10092014-143512211
Persistent URL:http://resolver.caltech.edu/CaltechTHESIS:10092014-143512211
Default Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:8688
Collection:CaltechTHESIS
Deposited By: John Wade
Deposited On:09 Oct 2014 22:07
Last Modified:15 May 2019 23:50

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