with Number 100 black Epo-lux. The hexcel] inserts were used to prevent collected material from being subsequently swept out by winds and were black to aid in the location of ind.vidua fallout particles, the majority of which were expected to be light in color. The hexcel! was coated, and the aluminum tray was lined to obtain chemically inert surfaces from which the fallout material could be easily removed. Upon recovery, the trays were closed with a preformed polyethylene lid over which was placed an aluminum cover; the whole assembly was then temporarily sealed by means of a gasket of surgical tubing, which was compressed by external pressure maintained by two cloth cinches (Figure 2.7). The polyethylene liner and lid were later permanently heat-sealed together. With an aluminum cover banded to the tray, the sealed assembly could maintain internal pressures of 7 psi indefinitely. The AFI was installed on the instrument plattorm aboard the DD-592 (Figures 1.16 and 2.8). The present model represents the redesign of an instrument used during Operation Redwing (Reference 33). The original design was modified to obtain a more complete series of fallout and base surge samples. The instrument used a series of chemical filters so designed that any large amounts of water arriving with fallout would be immediately removed from the solid material and stored in a separate water reservoir (Figure 2.9}. Dimethylterephthalate (DMT), recrystallized into its acicular form, was uSed as the filter material (Reference 65). Sucha filter had been determined to have a high efficiency for 0.3-micron-diameter particles and permitted later recovery of solids by Sublimation. The filter head is 334 inches in diameter (inside diameter, 3.55 inches), uses a 34-inch filter bed of DMT cryStals, and is known to withstand very heavy rains (50 in/hr) without plugging or loss of efficiency. The filter also is so designed that both the solid and the liquid fractions, together with all surfaces contacted, can be shipped as a single sealed package (Figure 2.9). Mechanically, the AFI can be considered as an assemblage of the following units: the filter heads and the filter-head-raising mechanisms, the pneumatic system, the vacuum pumps, the vacuum switching valves, the recording flow meters, and the control box. The instrument has a series of 30 filter heads, each covered when not actually sampling, and each raised above the level of the other heads when drawing a Sample. All heads sample vertically at a conStant rate of 10 ft?'min. One series of 10 heads sampled in numerical sequence for intervals of 10 minutes each, the entire sequence being started at zero time by the control box. A second series of 20 heads sampled in numerical sequence for intervals of 2 minutes each, the entire sequence being triggered by a preset increase in background. Flow through the filters is maintained by a pair of constant-flow vacuum pumps, which have a line-vacuum- sensing control valve to compensate for increases in pressure drop across the filter due to filter loading. By means of the vacuum-switching valves, this controlled vacuum is applied only to the chamber containing the water reservoir of the filter actually sampling, thus minimizing vacuum evaporation of the water fraction. A pair of recording Flow-rators are incorporated into the vacuum lines of both the short and the long interval filters. The AFI control box governed and recorded the filtering sequences and the other instruments on the DD-592 platform. The activities of all platform instruments including the AFI flow rates were automatically recorded by the AFI control box, So that all samples collected could be correlated intime. The AFI control box was in turn activated by EG&G radio signals received at minus 5 minutes, minus 1 minute and minus 5 seconds. The FS’s were installed at various locations aboard barges or on islands and were specifically designed for very early recovery. They Simply consisted of a large polyethylene funnel (2.6-ft? collecting area), which was fitted into a 2-gallon polyethylene bottle. The bottles were mounted on top of a 10-foot pipe stand in a special bracket that permitted helicopter recovery. Helicopter pickup was effected by snagging a 2-foot diameter sphere made of two hoops welded at right angles. The bottles were set in the previously installed stands just prior to shot time SO that the collection of extraneous material before the shot would be reduced to a minimum. 2.2.7 Instrument Control. All project instrumentation was activated upon receipt of an EG&G radio signal at the instrument control box (ICB). This control box, designed for installation aboard the coracles, started both the standard and the underwater GITR’s, provided 63