the amount of water in it [edit or gas the new one use H gas]
water H2O is an eazy way to store H to heat up and form He
first one needs an atom bomb that splits Plutonium-239 aka undergoes fission
and triggers a fusion reaction in the H by compression of the core of the H-bomb by the A-bomb
do it right the a-bomb outside compresses center core H-bomb
the amount of water [or gas] in the center varys the yield more water = more H = more BANG
NOW THERE IS A LOT MORE TO IT REFLECTING NEUTRONS H IS NOT COMMON HYDROGEN
THERE IS A BIT OF Li IN THE HEAVY WATER
BUT LETS KEEP THE STORY SIMPLE
MORE WATER [or gas] MORE BANG
[This message has been edited by ray b (edited 03-27-2022).]