2.4.13 UW-1 The UW-1 underwater instruments functioned excellently. When check calibrated, they were found to retain accuracy with no drift. 2,4,14 Rad-Chem Trailer Equipment The radiation measuring equipment in the Rad-Chem trailers functioned adequately. The Berkley Model 2000 scalers presented some trouble, but were generally accurate and reliable. These units were calibrated and tested with a Rutherford Model 300 pulse generator using a 0.25 volt, 1ms rise time, 2 msduration, negative pulse, The best GM tube was the Tracerlab TGC-2 with a window thickness of less than 2 mg/cm’, which gave counting efficiencies of from Z0 to 30 percent, The alpha counter head and amplifier-power supply system functioned well for low level alpha counting, providing good discrim- ination against beta and gamma pulses. The laboratory monitor, SU-3B, was used to monitor bench tops and miscellaneous items. Initially the voltage regulation at the Site Elmer trailer was poor, due to a defective Sorenson voltage regulator. The voltage reg- ulation stability was carefully examined with a fast trigger oscilloscope, and line disturbances were damped out by careful tuning to resonance, 12