Test:Yankee; Date:May 4, 1954;The test device used in Yankee test had codename Runt II. Which was the proof test of the TX/EC-24. RUnt II design was very similar to that of Runt I, used earlier in Romeo shot. All major components in both devices were identical except the thermonuclear fusion fuel. Romeo's Runt I used natural Lithium, to be precise 7.5% Li6 and Runt II used partially enriched Lithium 37%-40% Li6. As you can see it was the same fuel used in Bravo test. Other than that, both devices were 61 inches wide and 225 inches long and weighed 39,600 lb using RACER IV primary.
Runt II was included in the test schedule after Runt device's extremally successfull testing. Secondly, two other test devices(Ramrod and Jughead) have been removed from test schedule, because Bravo and Romeo tests instantly made cryogenic fuel thermonuclear weapons obsolete. As with its predecessors Yankee test has been more than successfull. Projected yield of this device was 9.5 Mgt with the range of 7.5-15 mgt. Actual yield was 13.5 Mgt. Which was the second largest test ever detonated by US. The fuel substitution led to significant yield increase - 63%, and it was completely due to fusion reaction. Although not the most powerful in the test, Yankee was the "cleanest" device tested during the operation Castle. It had the highest fusion yield of all the devices.
Immense explosion created gigantic mushroom as well. During the first minute of explosion the cloud reached 34, 000ft in height and 6.5 mile in diameter. Eventually the cloud would rise to 110, 000ft.
Mark 17/24 thermonuclear bomb which was a result of Yankee test, was stockpiled by US from 1954 till 1957 and yielding between 10-15 megatons.