Project Y: the Los Alamos Story - Edith C. Truslow, Ralph Carlisle Smith
Edith C. Truslow, Ralph Carlisle Smith - Project Y: the Los Alamos Story, p.275.
[For "Able", "Baker", and "Charlie" tests at the Bikini atoll in 1946 the Los Alamos agreed to make] at least one definite estimate of the weapon's equivalent high-expiosive yield. It was decided to attempt this by radiochemical methods, photographic methods (for the air burst), and fast neutron measurements (for the air burst). The technique of estimating yield from blast measurements was assigned to the Navy Bureau of Ordnance. The underwater burst presented the greatest measurement problem because of possible failure of the radiochemical technique. This problem was particularly serious because no weapon had ever been detonated using water as the surrounding medium. Also, it was not known whether an atomic weapon would transfer energy to a denser medium exactly as it would transfer energy to air. Accordingly, one timing measurement was to measure the time from first current to the detonators to first appearance of ionization due to the gamma rays emitted by the bomb. A proper value of this time would indicate "normal" performance, whereas too small or too great a value would suggest "subnormal" performance. Fortunately, the radiochemical technique was successful, and the time measurement merely supported the radiochemical observations.
[For "Able", "Baker", and "Charlie" tests at the Bikini atoll in 1946 the Los Alamos agreed to make] at least one definite estimate of the weapon's equivalent high-expiosive yield. It was decided to attempt this by radiochemical methods, photographic methods (for the air burst), and fast neutron measurements (for the air burst). The technique of estimating yield from blast measurements was assigned to the Navy Bureau of Ordnance. The underwater burst presented the greatest measurement problem because of possible failure of the radiochemical technique. This problem was particularly serious because no weapon had ever been detonated using water as the surrounding medium. Also, it was not known whether an atomic weapon would transfer energy to a denser medium exactly as it would transfer energy to air. Accordingly, one timing measurement was to measure the time from first current to the detonators to first appearance of ionization due to the gamma rays emitted by the bomb. A proper value of this time would indicate "normal" performance, whereas too small or too great a value would suggest "subnormal" performance. Fortunately, the radiochemical technique was successful, and the time measurement merely supported the radiochemical observations.