Chapter 2
PROCEDURE
2.1
OPERATIONS
Table 2.1 lists shot participation and instrumentation. The instrument stations were
placed in previously prepared positions at the latest practicable time prior to each shot
and were recovered postshot as soon as Rad-Safe conditions permitted. The residual
stations were activated upon placement. Their 5-day operating period allowed for 2
days of data-recording and three 1-day shot delays.
For the surface bursts, the initial
stations were activated by a minus-i-minute-timing signal for warmup, and a minus15-second signal to start the recorder. Shot Zuni was an exception; only a minus~-1-
second signal was available to start the recorder.
Timing signals were necessary on
the initial stations because of the limited recording time available (Cook Research
Laboratory MR 33 recorders, 4 minutes; Sanborn recorders, 15 minutes). For Shot
Cherokee, the recorders were noi started until after the device release.
2.2.
INSTRUMENTATION
In designing instrumentation for this project, there were two objectives: (1) to design
instruments to best fulfill the requirements; and ‘2) io design Mexible instruments readily adaptable to u wide variety of field measurements. In view of this dual objective, the
instruments were designed to be compact, drift-free, reliuble, wide in dynamic-range
coverage, and low in cost. The basic circuit evolved measured discrete increments of
charge.
Essentially, this circuit could be used with any sensing element that had an out-
put which was a known function o« the radiation field. Thus, the circuit was equally
applicable to ion chambers, scintillation detectors, or phote-conductive crystals.
In operation, the charge on C, (Fizure 2.1) held tube T; well beyond cutoff. The output
current of the sensing element discharged C, at a rate dependent upon the radiation level.
Whenthe voltage ut the grid of T; reached the grid base, T, conducted, fed a negative signal to the grid of T., aud initiated a regenerative action which rapidly cut off T,. Then C;
charged to a potential equal to B-plus tess the cathode voltage and the grid-to-cathode
drop through the diode action of the grid of T;. When C; was completely charged, the
circuit returned to its normal! condition of 1, conducting ani T, cutoff.
The circuit
remained in this condition until Cy was once more discharged by the output of the sensing
element. The output of this circuit consisted of pulses that had a repetition rate proportional to the output current of the sensing element.
2.2.1 The Residual Instrument System, Conrad 1 Detector.
gamma-exposure rate from fallout contamination is given by:
In general, decay of the
l=1,t*
Where:
(2.1)
I= the gamma-exposure rate at time t
I, = the gamma-exposure rate at unit time
x = the decay constant (given as 1.2 for gross fission products)
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