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