title: Castle Bravo
context: Castle Bravo was the first in a series of high-yield thermonuclear weapon design tests conducted by the United States at Bikini Atoll, Marshall Islands, as part of Operation Castle. Detonated on March 1, 1954, the device was the most powerful nuclear device detonated by the United States and its first lithium deuteride fueled thermonuclear weapon.[1][2] Castle Bravo's yield was 15 megatons of TNT, 2.5 times the predicted 6.0 megatons, due to unforeseen additional reactions involving 7Li,[3] which led to the unexpected radioactive contamination of areas to the east of Bikini Atoll.
question: What was the last high-yield thermonuclear weapon design test conducted by the US at Bikini Atoll?
answers: Castle Bravo