HASL AERIAL SURVEY SYSTEM
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INTRODUCTION
The measurement of fall-out over extensive areas has become
necessary in view of the increased yield of radioactive debris from
the larger nuclear devices,
The use of aircraft for long range
radiation survey makes feasible a rapid determination of the dise
tribution of fall-out debris,
The limit of detectability depends on
the sensitivity of the measuring instrument, the energy and intensity
of the surface radioactivity and the absorption of the intervening
layer of air,
When the altitude is known, it is then possible to
relate an aerial radiation measurement to the intensity at the surface.
The resolution, that is, the degree at which an area can be
de linea ted is proportional to the aircraft altitude,
The radius of
the ground area in feet which is viewed by the detector is approxe
imately equal to the aircraft altitude in feet,
Since fall-out is
distributed fairly wiformily over wide areas, the aircraft reading
is directly related to the surface radiation field,
This aerial survey system uses a scintillation cowmter which
is sensitive over a range extending from 0,005 mr/hr to 200 r/nr,
as measured in the aircraft.
A signal from the airplane radar
altimeter corrects the aircraft radiation reading to a radiation
intensity at three feet from the surface.
This level is recorded
and simultaneously converted to a time=-modulated pulse-train by a
“Telepulse” Coding Unit for radio transmission to a plot center.
At this center, a "Telepulse* Receiving Unit decodes the information
and presents the ground-level radiation intensity on a strip=chart
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