CHAPTER 4 .
RESULTS
The densitometer at Station 690.01 did not function properly. The recording camera did
not run, as shown bythe film footage indicator and the unexposed section of film following the
record of voltage calibration made just prior to closing the station on M—5 days.
The densitometer at Station 690.02 functioned successfully. The data obtained are given in
a later paragraph.
At Station 690.03 the camera ran, but the timing oscillator and the oscilloscope were
never turned on. At Station 690.04 all components operated, but in reversed timing sequence
so that the camera power was turned off before the blast wave arrived.
The instruments and instrument stations withstood the stresses due to heat and blast.
The only damaged parts were the two front guy wires in Station 690.01, which were snappea and
bent. However, the source holder was undamaged and the relative pcaition of the beta source
and detector was unchanged. Stations 690.01 and 690.02 were washed over. Both were covered
with coral rock and sand on recovery. Washing over, obviously, must have occurred long after
biast arrival, or else the record at Station 690.02 could not have been obtained.
An enlargement of a portion of the densitometer film record at Station 690.02 is shown in
Fig. 4.1. As was predicted, zero time, characterized by a burst of gamma radiations, was
distinctly identified on the record by a discontinuity of the beta trace. The electron beam recording the beta signal was driven off the oscilloscope screen but came back to its preshot
position in approximately 0.30 sec. It remained at this position until the blast arrival.
The noise-monitoring trace remained at the same level from the start to the finish of the
record run, thus proving the relative immunity of the circuit components from electromagnetic
disturbance and other spurious signals.
From the densitometer record at Station 690.02, the following data were obtained (Fig. 4.1):
Time of blast arrival, 9.86 sec
Density at H + 9.86 sec, 1.76 g/liter
p/p, at H + 9.86 sec, 1.53 + 0.03
(where p, is the density of unshocked air and p is the density of the material along the
beta path)
Maximum density messured (at H + 12.01 sec), 9.20 g/liter
Maximum p/p, measured (at H + 12.01 sec), 8.00
In general, during the period 0.1 to 3.5 sec after blast arrival, the material density varied
randomly (suggesting swirling and turbulence) from about 2.5 to 4.3 times preshot atmospheric
density. This indicates considerable loading of the air by dust, pebbles, coral, rock, and other
debris.
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