For the Conrad I detector, n = -2, and:
Ar . -2At
(2.7)
t
r
In practice, at high-pulse~repetition rates, a number of pulses N over a period T
were used to read out the data. Hence, from equation 2.5:
Ar . (Nt + Atv? - (Nt)?
int)?
Ar . (T+ Atj® - (T)P
r
(2.8)
= fat
T
Where:
At nowincludes all errors in reading the time interval T.
The time-base error for the Conrad recorders was +0.069 percent; therefore, the
readout error was negligible, and the errors of the Conrad I system (of the order of
10 percent) could be attributed to the detector itself.
For the Gustave I system, n = -1, and:
Sr. rat
r
T
(2.9)
Hence the Gustave I system error was essentially that of the detector (the time-base
error £0.02 percent), and was of the order of 10 percent.
2.4
BEACH-BALL-KADIATION-DETECTOR-TELEMETER UNIT
To attain the objective of measuring the residual-exposure rate on the crater of a
land-surface burst, a droppable radiation-detector-telemeter unit was devised. A
Gustave I detector system was connected to key a 1, -watt VHF transmitter that had
been constructed in the field.
The detector and transmitter were mounted in a poly-
ethylene bottle suspended at the center of an air-inflated, 5-foot, plastic beach ball.
The beach ball was attached to a 27-pound lead brick by means of a 6-foot line. This
made it possible to drop the system from a helicopter more accurately with a minimum
of impact shock to the instrumentation. The lead brick hit the ground first and allowed
the beach ball to slow down over the 6-foot distance before hitting the ground.
In ad-
dition, the beach ball itself acted as a good impact absorber. Once the beach ball was
released, the helicopter could go a short distance away and orbit in a radiologically
safe region, while receiving the data transmitted from the beach~ball unit.
26