CHAPTER 2 EXPERIMENT DESIGN 2el DESIGN CRITSRIA 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 taat the maximum radius of the surge from the CASTLE devices could be from 15,000 to 34,000 ft, depending upon the yleld 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 instrumented for dbase 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 fall=out cellectors in the region were ruggedly built. These collectors were set for I-min intervals. &xperience 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 occu more than 6 hr after the detonation, which was the maximum sampling time of the IVY collector. Thus, two collectors were generally placed at each stations (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-nin intervals for a total time of 12 hr. Basically, the same type of instruments were used to sample falle out on the surface land and surfece water shotSe 2.2 THE INTERMITTENT FALLOUT COLLECTCR The intermittent fallout collector (IFC) consisted of a circular dise (or "spider") divided intc 24 sectors, a driving and timing mech- anism and a housing (Figs. 2.1-2.3). ach sector contained a triangu~- lar tray 3 3/7 ine x 10 in., anu 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