CHAPTER 2 EXPERIMENT DESIGN 2el DESIGN CRITARIA The collectors were designed to collect liquid and solid fallout samples at preset, successive time intervals which could be adjusted to between 1 min and 30 min. The samples were at least large enough to be analyzed by standard counting techniques. Base surge estimations from work done by the Naval Ordnance Laboratory Task 152 indicated that the maximum radius of the surge from the CASTLE devices could be from 15,000 to 34,000 ft, depending upon. the yield of the devices. The phenomena should he complete within 10 or 15 min after detoration. The base surge was primarily expected from the surface water shots; however, Shot 1, detonated on a reef, was in~ strumented for base surge samples because it was thought that the reef was so narrow that the shot would be, in effect, a water shot. Since high overpressures are encountered in the base surge region, the fallout ccllectors in the region were ruggedly built. These collectors were set for l-min intervals. Experience at IVY_3/ indicated that the heaviest fallout on the atoll cccurred within the first 30 min after the detonation and thet fallout continued to occur more than 6 hr after the detonation, which was the maximum sampling time of the IVY col- lectore Thus, two collectors were generally placed at each station: (1) one sampling at l-or—5=<min intervals for a total time of 24 min or 2 hr respectively, to document the base surge or early fallout; and (2) the other sampling at 30-min intervals for a total time of 12 hre Basically, the same type of instrumenis were used to sample falle out on the surface land and surfece water shotse 2e2 THE INTERMIITENT FALLOUT COLLECTCR The intermittent fallout collector (IFC) consisted of a circular disc (or "spider") divided intc 24 sectors, a driving and timing mech- anism and a housing (Figse 201-203). Each sector contained a triangu~ lar tray 3 3/7 ine x 10 in., ano 3/4 in. deep. One tray at a time was exposed to fallout throwh an opening of equal size in the top covere The wide end of each tray held four glass counting cups (1 in. in 17