26
detonation.
Little,
if any,
correlation exists between the probe values
and the actual levels of radioactivity present in sea water 4s
determined from samples taken curing the Marsh expedition (Fig. 7).
The lack of sensitivity might possibly have been due to faulty
"a" and "B" pattertes in the probe assembly although this is not
likely.
The instrument was sensitive to a J source inserted into
the calibration port several times throughout the duration of the
trip.
Although the instrument,
in its present form, cannot be used
for detecting low levels of contamination the following modifications might be made to increase its sensitivity and usefulness.
1.
Incorporate suitable voltege stabilization circuits in
the filament, B+, and high voltage supplies (the ship-
line supply fluctuates from 80 v to 135 v).
2.
Replace the present crystal and photomultiplier with a
7-inch diameter unit.
3.
Rebuild the water tank to minimize vibration effects on
the scintillation probe and inorease the volume of water sround the probe,
4k,
Inoorporate intermediate ranges into the control box
with the following ranges: 5, 30, 50, 300, 500 and 3000
microroentgens.
Fish
Levels of radioactivity in fish tissues are given in Table
4,
They are remarkably uniform in the three skipjack taken near
station 23; the liver has the highest level of activity, 186 a /efg
a
at