were activated by removalof the battery potential from the dosimeters during various intervals of the first minute after the detonation. The dosimeters recorded the radiation that arrived after they were activated. The devices were mounted vertically in a plastic and aluminum frame (Figures 2.4 and 2.5). A spring-loaded solenoid was below each dosimeter, mounted so that it depressed the charging pin at the base of the quartz-fiber dosimeter. A battery charged the dosimeters to zero reading. Upon activation, a Hayden chronometric motor programmed the operation. The latching solenoids were activated in intervals of about 2 seconds, varying with position and event. The charging potential was removed from the dosimeters, thus the dosimeters integrated the exposure that arrived after the activation time. Several dosimeters were included to read the total exposure. One dosimeter was activated at 58 seconds after the detonation to give an estimate of the effects of residual radiation. At 60 seconds, a solenoid-release mechanism caused the entire instrument to drop down the 8-inch steel-pipe stations to 6 feet below the surface. Thus, the instruments were shielded from most of the residual radiation. The device was housed in an aluminum canister 32 inches high and 7-Y, inches in diameter, with a 0.10-inch wall thickness. The battery pack that powered the mechanism was in the bottom half of the canister. A 6-inch space at the top of the canister was utilized for the placement of various other dosimeters, and Project 2.51 gold and sulphur neutron detectors for Shots Zuni and Cherokee. The instrumcnt was activated when an eutectic element was melted by thermal radiation. The eutectic element consisted of two pieces of 0.008-inch brass shim stock, plated black with Ebanol-C, and soldered with Cerrolow 136, an eutectic that melts at 136 F. The total activation delay from time of detonation was estimated at ¥, second. 2.2.7 Mechanical Drop Mechanism. A mechanical drop mechanism wasinstalled in the pipe caps of someof the 4-inch and 8-inch steel-pipe stations. These stations were instrumented with five sets of dosimeters. Three sets were suspendedin the top of the station and fell to the bottom when activated. The first set of dosimeters was suspended by a black nylon string extending from an arm attached to the cap top through a hole in the cap. The gammadata indicated that the string burned through in about Y, secondafter the detonation. A second set of dosimeters was suspended by a wire from a piece of angle iron on top of the cap. The shock front activated this group. A third set of dosimeters was suspendedfrom a mechanical 60-second photographic timer. The timer was activated when the thermal radiation burned through a piece of black nylon string. The instruments dropped approximately 1 minute after the detonation. In addition, one set of dosimeters remained fixed at the top and another at the bottom of the station. The dosimeters were affixed in this fashion to afford an opportunity to measure the radiation up to the time of activation and then be dropped to the bottom of the pipe for shielding from residual radiation. Thus, the dosimeters integrated the dose received up to the time of arrival of thermal and shock pulses, the dose received up to 1 minute, ant total radiation. 2.2.8 Station Layout, Utilization, and Construction. The station layout and utilization are given in Table 2.3. The station construction is shown in Table 2.4, since the amount of shielding surrounding the detector was of importance in the data analysis. Series 210 stations consisted of an 18-inch open-end aluminum cylinder mounted 36 inches above the ground on a 2-inch-diameter aluminum rod. The dosimeters were retained by a bolt at each end of the cylinder, Series 210, 211, 212, and 213 stations were constructed of steel pipe capped at both ends, The pipes were mounted vertically in the ground with the exception of Series 212, where the pipes were mounted vertically in the center of a 6-foot concrete cube, the surface of which was flush with the ground, Series 113 stations were located on the coral reef east of Site Charlie and were constructed of steel pipe. These stations were primarily for use by Project i.1 but were utilized by Project 2.1 for Shots Cherokee and Tewa. 18