ruggedized like the PAC 15, the instrument was much more sensitive, using an
air chamber with an effective area of 100 em” and an aluminized (on both sides)
mylar effective window thickness of 0.85 me/om’.
Also, the probe guard was
half again as thin as the PAC-15 probe and enabled near contact measurements
of surfaces to be made.
objects.
The air chamber was also subject to damage by sharp
More so, in fact, than the PAC-1S.
However, unless a large hole
Lad been torn in the mylur it was still serviceable.
The detector was connected to a nonruggedized survey meter which had
three ranges, 0-1,000, 0-10,000, 0-100,000 counts per minute, full scale
with 27mgeometry.
Both the PAC-1S and the LLL "Blue Alpha Meter" were calibrated on 239py,
Alpha sources, attached to the survey instruments were used for field checking.
2.
FPeta-Gamma Detectors.
Two instruments were used for beta-gamma detection capability, the
E-400B, G-M survey meter and the Ludlum Model 3 survey meter with a modified
Model 44-9 "Pancake" G-M probe.
These instruments were used to obtain contact
readings on contaminated/activated radioactive scrap.
ae
E-500B.
This instrument is a portable Geiger counter used for con-
ducting beta-gamma radiation surveys.
A tube sensitive to lower level gamma and beta radiation is located in
the external probe.
Discrimination between the two types of radiation is
made by means of a rotary shield on the probe.
off at 0.31 MeV.
The probe has an energy cut
The instrument was calibrated for gamma fields using
137s.
b.
\
4
Ludlum Model 3, with Model 44-9 Pancake Probe.
This "thin window"
detector was used for low energy gamma and beta radiation detection on scrap.
The survey meter itself was used only as a relative indicator of contamination
levels,
®
“
The Model 44-9 Pancake Probe uses an LND 7311/8767 detector with an
Gf