Operation Latchkey

Operation Latchkey was a series of 38 nuclear tests conducted by the United States in 1966–1967 at the Nevada Test Site. These tests followed the Operation Flintlock series and preceded the Operation Crosstie series.

Persimmon
Persimmon included a vertical line-of-sight pipe fitted with a fast-acting closure. At the time of detonation, this vacuum pipe provided a pathway for neutrons from the nuclear device to travel to instruments in a tower located above the shot hole. A few seconds after detonation, these instruments and their samples were dragged out of the tower on a sled, before the subsidence crater formed and destroyed the tower.