50
20
10
N
_—_ 50
&
2 {%
"1S 20
oO
\
a
\
~~”
G
o
1.0
N
LL.
i.
Li
0.6
N
0.2
0.1
10
20
50
100
200
500
1000
ENERGY (keV)
FIGURE 3-6. A TYPICAL DETECTOR EFFICIENCY VERSUS ENERGY CURVE FOR THE
HPGe PLANAR DETECTORS USED AT ENEWETAK.
Conversion factors, in units of pCi/g per cps, can be obtained for these radionuclides, as well as any
others which might be present in detectable quantities, by using Equation (8) in Section 3.2.5 with
the appropriate input parameters. Figure 3-6 shows a typical detector efficiency (A,) curve for the
HPGe planar detectors which were used at Enewetak.
Angular response data, R (6), were also
obtained for a number of gamma ray energies. Figure 3-7 shows the results for 662 keV gamma rays
from 137Cs with and without the collimator. Although the collimator does have a significant effect
on the angular response, it was not thick enough to provide complete cutoff at the higher energies as
it did for the 60 keV gamma rays from 24lam (see Figure 3-3).
100