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INTRODUCTION
A method of thin source (i.e. less than the alpha particle range)
nrenaration of samples utilizing a ZnS screen and phototube counting was
developeu.
The counting procedures are the same as for tne method using
thick sources described by Turner et. al. (1), and applied by several
investigators [Turner (2); Cherry (3), (4); Hasson and Cherry (5);
Shannon and Cherry (6)].
Applications of the thin source counting
technique have been made by Osanov and Popov (7) and Curtis and Heyd (8).
Estimation of the range of the alpha particles in the sample and
the detection screeen, and inhomogeneity problems in source preparation
constitute the greatest errors in the accurate determination of alpha
concentrations in sclids.
These problems were reviewed by Cherry (9),
who concluded that the alpha particle ranges in non gaseous media are
complicated and have not been well defined for general application.
The range of an alpha particle in any medium is a function of the
atomic number (Z) of the medium, and the energy (£) of the alpha particle
emitted.
Hence, in environmental samples, the mean value of each of
these two variables, wnich is determined from the composite proportions
of the individual components (Z and E), is needed since only one nuclide
and/or one elemental absorber is rarely present.
In the coralline atoll of
Bikini and matrix of the absorber is constant from sample to sample.
The Z of calciu.. carbonate, which constitutes the sediments of coralline
environments, on an atom fraction basis, is 10.0.
EXPERIMENTAL METHODS
A dried subsample (5-15%) of each sediment sample was ground to a