Chapter 2 PROCEDURE 2.1 SHOT PARTICIPATION This project participated in Shots Cherokee, Zuni, Flathead, Navajo and Tewa. is given in Table 2.1. 2.2 Shot data INSTRUMENTATION The instrumentation featured standardized arrays of sampling instruments located at a vari- ety of stations and similar sets of counting equipment located in several different laboratories. Barge, raft, island, skiff, and ship stations were used, and all instruments were designed to document fallout from air, land, or water bursts. The standardized arrays were of two general types: major and minor. of both was to establish a basis for relative measurements. The overail purpose Major arrays were located on the ships, barges, and Site How; minor arrays were located on the rafts, skiffs, and Sites How, George, William, and Charlie. All major array collectors are identified by letter and number in Section A.1, Appendix A. Special sampling facilities were provided on two ships and Site How. The instrument arrays located at each station are listed in Table 2.2. 2.2.1 Major Sampling Array. The platforms which supported the major arrays were 15 or 20 feet in diameter and 3 feet 8 inches deep. Horizontal windshields were used to create uniform airflow conditions over the surfaces of the collecting instruments (Figures 2.1 and 2.2). All platforms were mounted on towers or king posts of ships to elevate them into the free air Stream (Figure 2.3). Each array included one gamma time-intensity recorder (TIR), one to three incremental collectors (IC), four open-close total collectors (OCC), two always-open total collectors, Type 1 (AOC,), one recording anemometer (RA), and one trigger-control unit (Mark I or Mark I). The TIR, an autorecyclic gamma ionization dosimeter, is shown dissambled in Figure 2.4. It consisted of several similar units each of which contained an ionization chamber, an integrating range capacitor, associated electrometer and recyclic relay circuitry, and a power amplifier, fed to a 20-pen Esterline-Angus operational recorder. Information was stored as a line pulse on a moving paper tape, each line correspondingto the basic unit of absorbed radiation for that channel. In operation, the integrating capacitor in parallel with the ionization chamber was charged negatively. Ina radiation field, the voltage across this capacitor became more Positive with ionization until a point was reached where the electrometer circuit was no longer nonconducting. The resultant current flow tripped the power amplifier which energized a re- cycling relay, actuated the recorder, and recharged the chamberto its original voltage. ApProximately Y, inch of polyethylene was used to exclude beta rays, such that increments of gamma ionization dose from 1 mr to 10 r were recorded with respect to time. Dose rate could then be obtained from the spacing of increments, and total dose from the numberof increments. This instrument provided data on the time of arrival, rate of arrival, peak and cessation of fallout, and decayof the radiation field. The IC, shown with the side covers removed in Figure 2.5, contained 55 to 60 trays with Sensitive collecting surfaces 3.2 inch in diameter. The trays were carried to exposure position by a pair of interconnected gravity-spring-operated vertical elevators. 19 Each tray was exposed