Operation Sunbeam was a series of four nuclear tests conducted at the United States of America's Nevada Test Site

Nevada Test Site

The Nevada National Security Site , previously the Nevada Test Site , is a United States Department of Energy reservation located in southeastern Nye County, Nevada, about northwest of the city of Las Vegas...

 in 1962. Operation Sunbeam tested a number of small, "tactical" nuclear warheads. Most notable of these was the Davy Crockett

Davy Crockett (nuclear device)

The M-28 or M-29 Davy Crockett Weapon System was a tactical nuclear recoilless gun for firing the M388 nuclear projectile that was deployed by the United States during the Cold War...

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The most notable milestone of Operation Sunbeam was that it was the last nuclear test series on the Nevada Test Site conducted in the atmosphere by the United States. Since Operation Sunbeam, specifically the Little Feller 1 test of the Davy Crocket, all US nuclear tests on the Test Site have been carried out underground in accordance with the Partial Test Ban Treaty

Partial Test Ban Treaty

The treaty banning nuclear weapon tests in the atmosphere, in outer space and under water, often abbreviated as the Partial Test Ban Treaty , Limited Test Ban Treaty , or Nuclear Test Ban Treaty is a treaty prohibiting all test detonations of nuclear weapons...

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The individual blasts were:

Name	Date	Size
LITTLE FELLER II	July 7,1962	< 20 kilotons
JOHNNIE BOY	July 11,1962	0.5 kt fission
SMALL BOY	July 14,1962	< 20 kilotons
LITTLE FELLER I	July 17,1962	< 20 kilotons