Xx temperature structure in the higher yield region, accurate determination of the yield of an explosion from the observed cloud height could not be determined, As previously discussed, some radioactive material could lay at lower altitudes, The distance below the primary cloud mass was in general, a function of the burst conditions, tut usually the amount decreased rapidly with increasing distance, Sampling aircraft with 15,000-foot altitude capability were suitable for the range yields and burst conditions discussed, For explosions with yields above 10 to 15 kilotons an aircraft of the B-29-type was marginal because of limited altitude capability. sample the lower portion of these clouds, considered Such aircraft could only An aircraft to sample the maximm altitude requirements foreseen was expected to operate sufficiently long at lower altitudes when required,’ Radiation Characteristics of Primary Clouds While there were some activities derived from the neutron activation of nonfissionable tomb components, associated equipment, or dirt from the explosion sight, the major source of gamma radiation energy within the cloud derived from the fission products created in the explosion, . ey ' padiation from this source decreased with time after burst, Gamma The rate of decrease of—the gamma radiatim flux within the cloud reflected both the radiation decay source and the rate of decrease of the volumetric concentration of the source material as a result of cloud dispersal, Although the radiation intensity within an atomic cloud at shot times ~_e % According to the familiar fission product decay law (Way-Wigner),. 205 APWUHO SVEH-2-003 po