A video of the 27 May 1956 “Yuma” test from Operation Redwing. This was a small “boosted” fission bomb… 5 inch diameter, designed for air defense use (back when nuking formations of Soviet bombers seemed like it was going to be a thing). The process was that a small fission explosion would set off a small fusion booster… not quite a true H-bomb. In an H-bomb, the fission bomb is “merely” the trigger… a several kiloton fission bomb sets off up to many megatons of fusion explosion, with the fusion yield being up to 20 times that of the fission. In a boosted weapon, a sub-kiloton or low-kiloton fission bomb sets off the fusion booster which doesn’t itself amount to a whole lot of “bang,” but it releases a flood of neutrons which makes that fission explosion a whole lot more efficient and powerful. The neutrons released by the initial fission explosion can cause the lithium-6 in the lithium deuteride booster to fission into tritium; the conditions next to the fission blast are hot enough that the tritium will happily fuse with the deuterium, spitting out neutrons which will race back into the fission explosion and cause more of the plutonium to fission. (Done right, a surrounding case of non-fissionable depleted uranium can add to the power of the blast, as the high energy neutrons from the booster are powerful enough to cause U-238 to fission.)

It’s all well and good, but the resulting bang is a little less impressive when the fusion booster doesn’t actually go off. Which is what happened during the Yuma test, resulting in a paltry 0.19 kilotons yield. Data is sketchy, but I’d imagine the goal was to get close to one kiloton out of the device.