thicknesses of aluminum absorbers
Calibration of the pressurized
were placed over an array of dosimeters
ion chamber against a point
at three sites on Bikini Island.
source,
feather analysis of
A
the beta attenua-—
Opa
the method used with the
instrument in this study,
leads to
tion curves gave a maximum beta
about a 3% overestimate in the
energy between 1.5 and 2.2 MeV.
measurement of "typical'' environmen-
Given the known predominance of
tal fields in this country.
70,
r-
90
YY beta activities in the soil,
If a
similar correction were made to
this energy range is consistent with
90
these data,
The analysis also revealed that the
determinations (ion chamber and LiF
average beta contribution to the
TLD) would be within 10%.
total LiF exposure rates was 274% --
considered to be satisfactory
a vather significant contribution.
apreement between the two reference
Therefore,
techniques used in this work.
the 2.27 MeV
Y beta radiation.
it was necessary to reduce
the agreement of the twa
independent exposure-rate
This is
the LiF results by this amount to
Hence,
obtain the free-air gamma-ray
the Nal scintillation readings were
exposure rates.
normalized to the output of the
The comparison between the ion
on the basis of
these results,
pressurized ion chamber.
chamber results and the LiF gamma—
Fig.
3.
<A linear regression of the
two data sets gives agreement of
about 13% between the two methods.
One also finds that the correlation
of points in Fig. 3 is not as good
as
that in Fig.
2.
This difference
is most likely due to the beta contribution to the LiF results, which
may vary throughout the islands,
causing spread in the data.
oy
0
Departure from the 1:1 relationship
in Fig.
lon chamber response — uR/h
ray exposure rates is presented in
O
response or to insufficient
consideration of the ion chamber
30
Fig. 3.
40
50
4
60
|
7
80
Comparison of responses of
the pressurized ion chamber
with LiF TLD's.
The contribution due to cosmic radiation
has been
weducd
~—,
ane
a
‘Senet
data for energy dependence.
20
yy
LiF response — uR/h
3 may be due to an over-
correction of the TLD data for beta
10
to}
subtracted.