Appendix 8
DETAILS of MAJOR INSTRUMENTS
B.1
AERIAL RADIATION DETECTOR,
HASL TH-10-B
output of the telemeter is a 1,000-cps tone, gated on and
off within a l-second cycle.
The Top Hat aerial radiation detector is a scintillation detector utilizing plastic phosphors. The phos-
The ratio of on to off time
within the 1-second time inturval is proportional to the
input de signal.
phors are coupled to photomultiplier tubes, and the
integrated current output is amplified by a de amplifier
The amplifier has a logarithmic response and covers a
4-decade range of radittion intensity. By switching
between two photomultipliers which have different-size
phosphors, two ranges of 4-decades each are achieved:
Range A, 0.01 to 100 mr/hr, and Range B, 10 mr/hr
These bursts of 1,000 cps may be
coupled directly into the microphone input of a radio
transmitter or stored on an audio tape recorder.
A high-fidelity transmitter, U.S. Navy ART-13,
was used in the P2V-5 aircraft. It has an output power
rating of 100 watts.
Continuous operation is not possi-
ble because of heat dissipation limitations.
Also, the
transmitted signal blocks the receivers in the aircraft.
to 100 r/h.
The A phosphoris 3 inches in diameter and 3 inches
Therefore, the telemeter output, the gated 1,000-cps
high, and the B phosphor is ly, inches in diameter and
tone, is recorded on a tape recorder running at 3%-in/
to 1 ma and drives a strip-chart recorder, Esterline
recorder, which runs at 30-in/sec.
% inch high.
sec.
The output of each range varies f-om 0
Angus Co., AW.
The tape is then manually shifted to a playback
The recording
reel, containing up to 30 minutes of data, is played
The radiation calibration of a typical
unit is shown in Figure B.1. Both phosphors are collimated by an annular lead shield, which was added to
reduce the effect of aircraft contamination.
For a more detailed description of the instrument,
back through the radio transmitter in less than 4
minutes.
An electronically regulated power supply, HASL
TB-6-A, supplies all the voltages to the telemeter and
the detector control assembly. The regulators compensate for the varying 28-volt input power from the
see Reference 11.
aircraft generators.
B.2 ALTITUDE COMPENSATOR
The telemeter central station is connected to the
earphone output jack of a receiver, which is tuned to
The surface radiation reading, R; is related to the
the transmitter frequency.
aircraft reading, Ra/e, by a constant, fa, which de-
pends on the height above the surface.
Ra/c * f,-
bels of radia noise above the signal level.
However, the circuit current is related to
The indicated multiplica-
tion can be performed bythe addition of the logarithms:
Ry = Ia/etkh
Where:
This is
followed by a conventional ratemeter which converts
the logarithm of Rg/c, and the altitude, h, is proportional to the logarithm of fg.
The input to the central)
station has a noise filter, designed to reject 54 deci-
Thus, R; =
(200 <h <1,000)
the bursts of 1,000~-cps tone to a deflection of the pen
on a strip-chart recorder.
B.4 AUTOMATIC GAMMA MONITOR, HASL TN-4-C
[ is a current measured in milliamperes
The automatic gamma monitor is based on a detec-
k is a circuit constant
tor similar to the Top Hat aerial radiation detector.
The altitude-compenstion circuit electrically adds an
altitude signal, derived from the aircraft radio altimeter, APN-1, to the output of the detector circuit. The
aircraft radiation reading is continuously modified for
changes in flight altitude, and the surface readings remain proportional to the gamma intensity at 3 foet above
the surface.
A plastic phosphor is optically coupled to a photomultiplier, whose output is converted in a de amplifier to
a logarithmic response. The unit reproduces a radiation range from 1 mr/hr to 10 r/hr on a single scale.
The output is continuously recorded on an Esterline
Angus strip-chart recorder.
The monitor operates on
115-volt, 60-cps current and is completely sealed in
an immersionproof case.
B.3 TELEMETER, HASL TT-3-X
8.5 SCINTAMETER SURVEY METERS
The telemeter is connected in series with the stripchart recorder and converts its drive current, 0 to 1
ma direct current, to an alternating-current wave form
suitable for transmission through audio circuits. The
63
The scintameters are portable survey meters that
are powered by dry batteries and are completely selfcontained.