good. Not.sme NRL-operated instrument failed; at the LASL end 57 oscil- loscope chani®™ recorded out of a possible 61, and Bowen spectrograph ¢ ls operated. The total thermal radiation recorded on Orange was The time-interval measurement encountered similar difficulties as on feak, except that they were more severe. Both primary and secondary signals were recorded, but because of scattering in the deep cloud layer the time smear of the primary light pre_ vented the initial sharp rise required for a valid measurement. However unfolding of the otherwise well-written records should yield a useful number, The majority of the spectrographs and cameras registered either weak signals or none. However, three instruments (two NRL, one LASL) recorded relatively late time information which appears valuable. Also many photoelectric channels wrote a readable signal. These data describe qualitatively the fireball behavior from approximately 1 msec on. Aljlthough information for earlier times ia not entirely absent, it is very sketchy. Nevertheless there is a fair chance that one will arrive at a useful qualitative picture of Orange fireball development, especially if the spectroscopic data analysis can be supplemented by analysis of the EG&G high speed photographic records taken from airplanes. Program 11, Radiochemistry The objectives of Program 11 were (1) to determine the fission yield of the device, (2) to ascertain when possible what nuclear reactions take place in the device, (3) to study specific aspecta of the reactions by radiochemical tracers placed within the device, and (4) to determine the production of specific activities in certain areas of the devices arising from mate- rials included in them by design necessity or by intent. Samples of radioactive material from the cloud were obtained by manned aircraft equipped with specially designed sampling tanks, Radiochemical analyses were made at LASL to determine the fraction of the bomb included in the sample and the number of fission events. The fission yield was determined from these data. Analyses were made to determine the production of various radioisotopes of interest from the bomb materials or from detector samples placed in or near the device. The results of measurements of fission yields by various methods are included in Table 2.1. An investigation of water samples taken from the lagoon shortly after Walnut shot showed marked fractionation, indicating that such samples were not an adequate replacement for aircraft sampling. Program 12, External Neutron Measurements Program 12 was designed to determine the configuration of the active material of certain devices during the nuclear reactions by the Pinex tech- nique, whereby a neutron collimating "pinhole" is placed between the device and detector. A pinhole camera image of the device is formed on the detector, which is a sandwich of various materials to be activated by the neutrons. The sample may be cut into segments and counted on a scintlilation counter or placed against a photographic film to produce an autoradiographic image. 46 ¥0